COGENERATION CORP OF AMERICA
SC 13E3, 1999-09-24
COGENERATION SERVICES & SMALL POWER PRODUCERS
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<PAGE>   1

   As Filed With The Securities And Exchange Commission On September 24, 1999



                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                 SCHEDULE 13E-3

                        RULE 13E-3 TRANSACTION STATEMENT
              (PURSUANT TO SECTION 13(E) OF THE SECURITIES EXCHANGE
             ACT OF 1934 AND RULE 13E-3 ((S) 240.13E-3) THEREUNDER)

                       COGENERATION CORPORATION OF AMERICA
- --------------------------------------------------------------------------------
                             (Name of the Issuer)

                                NRG ENERGY, INC.
                       COGENERATION CORPORATION OF AMERICA
- --------------------------------------------------------------------------------
                      (Name of Person(s) Filing Statement)

                     COMMON STOCK, PAR VALUE $0.01 PER SHARE
- --------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                   628950-10-7
- --------------------------------------------------------------------------------
                      (CUSIP Number of Class of Securities)


        James J. Bender                             Julie A. Jorgensen
Vice President and General Counsel         President and Chief Executive Officer
        NRG Energy, Inc.                    Cogeneration Corporation of America
 1221 Nicollet Mall, Suite 700                 One Carlson Parkway, Suite 240
  Minneapolis, MN 55403-2445                     Minneapolis, MN 55447-4454
        (612) 373-5300                                (612) 745-7900

   (Name, Address and Telephone Number of Person Authorized to Receive Notices
           and Communications on Behalf of Person(s) Filing Statement)

                                   Copies to:

        Jeanine L. Matte, Esq.                     Bruce J. Parker, Esq.
        Pankaj K. Sinha, Esq.                 Kaplan, Strangis and Kaplan, P.A.
Skadden, Arps, Slate, Meagher & Flom LLP           5500 Norwest Center
      1440 New York Avenue, N.W.                 90 South Seventh Street
     Washington, D.C. 20005-2111                  Minneapolis, MN 55402
           (202) 371-7000                             (612) 904-5600



<PAGE>   2





     This statement is filed in connection with (check the appropriate box):

a. [x] The filing of solicitation materials or an information statement subject
to Regulation 14A, Regulation 14C or Rules 13e-3(c) under the Securities
Exchange Act of 1934.

b. [ ] The filing of a registration statement under the Securities Act of 1933.

c. [ ] A tender offer.

d. [ ] None of the above.

Check the following box if the soliciting materials or information statement
referred to in checking box (a) are preliminary copies:  [x]

                           CALCULATION OF FILING FEE


                Transaction Valuation       Amount of Filing Fee

                   $183,174,663.00               $36,634.93

[x] Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
and identify the filing with which the offsetting fee was previously paid.
Identify the previous filing by registration statement number, or the form or
schedule and the date of its filing.

Amount Previously Paid: $36,634.93

Form or Registration Number: Schedule 14A

Filing Party: Cogeneration Corporation of America

Date Filed: September 23, 1999



                                       2


<PAGE>   3


                                  INTRODUCTION

This Rule 13e-3 Transaction Statement on Schedule 13E-3 (the "Schedule 13E-3")
is being filed by NRG Energy, Inc., a corporation organized under the laws of
Delaware ("NRG"), and Cogeneration Corporation of America, a corporation
organized under the laws of Delaware ("CogenAmerica"), pursuant to Section 13(e)
of the Securities Exchange Act of 1934, as amended, and Rule 13(e) 3 thereunder,
in connection with the Agreement and Plan of Merger, dated as of August 26, 1999
(the "Merger Agreement"), by and among Calpine Corporation ("Calpine"), Calpine
East Acquisition Corp. ("Acquisition Sub") and CogenAmerica, pursuant to which
Acquisition Sub will merge with and into CogenAmerica, with CogenAmerica
continuing as the surviving corporation.

The following Cross Reference Sheet, prepared pursuant to General Instruction F
to Schedule 13E-3, shows the location in the Proxy Statement of CogenAmerica
filed with the Securities and Exchange Commission on the date hereof of the
information required to be included in this Schedule 13E-3. The information set
forth in the Proxy Statement, including all exhibits thereto, is hereby
expressly incorporated herein by reference as set forth in the Cross Reference
Sheet and the responses in this Schedule 13E-3, and such responses are qualified
in their entirety by reference to the information contained in the Proxy
Statement.

The information contained in this Schedule 13E-3 concerning CogenAmerica,
including, without limitation, information concerning the background of the
transaction, the deliberations of CogenAmerica's Board of Directors in
connection with the transaction, the opinion of CogenAmerica's financial
advisor, and CogenAmerica's capital structure and historical financial
statements, was supplied by CogenAmerica. NRG, Calpine and Acquisition Sub take
no responsibility for the accuracy of such information. The information
contained in this Schedule 13E-3 concerning Calpine and Acquisition Sub was
supplied by Calpine. CogenAmerica and NRG take no responsibility for the
accuracy of such information. The information contained in this Schedule 13E-3
concerning NRG was supplied by NRG. CogenAmerica, Calpine and Acquisition Sub
take no responsibility for the accuracy of such information.



                                       3
<PAGE>   4


                              CROSS-REFERENCE SHEET


         SCHEDULE 13E-3                         LOCATION IN PROXY STATEMENT
     ITEM NUMBER AND CAPTION                    ---------------------------
     -----------------------

Item 1(a)...................................    Outside Front Cover Page;
                                                QUESTIONS AND ANSWERS
                                                ABOUT THE MERGER; SUMMARY -
                                                The Companies

Item 1(b)...................................    SUMMARY - The Special Meeting;
                                                THE SPECIAL MEETING - Record
                                                Date; Voting Power; Votes
                                                Required

Item 1(c)...................................    HISTORICAL MARKET INFORMATION

Item 1(d)...................................    HISTORICAL MARKET INFORMATION

Item 1(e)...................................    Not applicable.

Item 1(f)...................................    Not applicable.

Item 2(a)-(d),(g)...........................    Not applicable.

Item 2(e)-(f)...............................    Not applicable.

Item 3(a)(1)................................    Outside Front Cover Page;
                                                SPECIAL FACTORS -
                                                Background of the Merger; -
                                                Reasons for the Merger; -
                                                Conflicts of Interest -
                                                Arrangements with NRG


                                       4

<PAGE>   5

Item 3(a)(2)and(b)..........................    Outside Front Cover Page;
                                                SUMMARY - Recommendations of the
                                                Independent Directors
                                                Committee and the Board of
                                                Directors; SPECIAL FACTORS -
                                                Background of the Merger; -
                                                Reasons for the Merger;
                                                -Conflicts of Interest -
                                                Arrangements with NRG

Item 4(a)...................................    QUESTIONS AND ANSWERS
                                                ABOUT THE MERGER; SUMMARY -
                                                Terms of the Merger
                                                Agreement; SPECIAL FACTORS -
                                                Purpose, Timing and
                                                Structure of the Merger;
                                                SUMMARY OF MATERIAL FEATURES
                                                OF THE MERGER

Item 4(b)...................................    QUESTIONS AND ANSWERS ABOUT THE
                                                MERGER; SUMMARY - Terms of the
                                                Merger Agreement; SPECIAL
                                                FACTORS - Purpose, Timing and
                                                Structure of the Merger; SUMMARY
                                                OF MATERIAL FEATURES OF THE
                                                MERGER; SUMMARY OF MATERIAL
                                                FEATURES OF THE CALPINE/NRG
                                                AGREEMENT

Item 5(a)-(b)...............................    SUMMARY - Terms of the Merger
                                                Agreement; SPECIAL FACTORS -
                                                Background of the Merger; -
                                                Plans for CogenAmerica After
                                                the Merger; - Conflicts of
                                                Interest - Arrangements with
                                                NRG; SUMMARY OF MATERIAL
                                                FEATURES OF THE MERGER;
                                                SUMMARY OF MATERIAL FEATURES OF
                                                THE CALPINE/NRG AGREEMENT


                                       5

<PAGE>   6

Item 5(c)-(d)...............................    SUMMARY - Terms of the Merger
                                                Agreement; SPECIAL FACTORS -
                                                Purpose, Timing and Structure of
                                                the Merger; - Plans for
                                                CogenAmerica After the Merger;
                                                SUMMARY OF MATERIAL FEATURES OF
                                                THE MERGER; SUMMARY OF MATERIAL
                                                FEATURES OF THE CALPINE/NRG
                                                AGREEMENT

Item 5(e)...................................    QUESTIONS AND ANSWERS ABOUT THE
                                                MERGER; SUMMARY - Terms of the
                                                Merger Agreement; SPECIAL
                                                FACTORS - Purpose, Timing and
                                                Structure of the Merger; -
                                                Plans for CogenAmerica After the
                                                Merger; SUMMARY OF MATERIAL
                                                FEATURES OF THE MERGER; SUMMARY
                                                OF MATERIAL FEATURES OF THE
                                                CALPINE/NRG AGREEMENT

Item 5(f)-(g)...............................    QUESTIONS AND ANSWERS ABOUT THE
                                                MERGER; SUMMARY - Terms of the
                                                Merger Agreement; SPECIAL
                                                FACTORS - Purpose, Timing and
                                                Structure of the Merger; SUMMARY
                                                OF MATERIAL FEATURES OF THE
                                                MERGER; SPECIAL FACTORS -
                                                Certain Effects of the Merger

Item 6(a) and (d)...........................    SUMMARY OF MATERIAL FEATURES OF
                                                THE MERGER - Financing of the
                                                Merger; Source of Funds

Item 6(b)...................................    EXPENSES OF THE TRANSACTION


                                       6


<PAGE>   7




Item 7(a)-(c)..............................     SUMMARY - Potential Benefits and
                                                Detriments of the Merger to
                                                Unaffiliated Stockholders;
                                                Benefits to Insiders; SPECIAL
                                                FACTORS -  Background of the
                                                Merger; - Purpose, Timing and
                                                Structure of the Merger;
                                                - Reasons for the Merger;
                                                - Perspective of NRG on the
                                                Fairness of the Merger

Item 7(d)..................................     SUMMARY - Potential Benefits and
                                                Detriments of the Merger to
                                                Unaffiliated Stockholders;
                                                Benefits to Insiders; SPECIAL
                                                FACTORS - Background of the
                                                Merger; - Purpose, Timing and
                                                Structure of the Merger;
                                                - Reasons for the Merger; -
                                                Perspective of NRG on the
                                                Fairness of the Merger; SUMMARY
                                                OF MATERIAL FEATURES OF THE
                                                MERGER - Federal Income Tax
                                                Consequences of the Transaction

Item 8(a) .................................     QUESTIONS AND ANSWERS ABOUT THE
                                                MERGER; SUMMARY -
                                                Recommendations of the
                                                Independent Directors Committee
                                                and the Board of Directors; -
                                                Opinion of CogenAmerica's
                                                Financial Advisor; SPECIAL
                                                FACTORS - Background of the
                                                Merger; - Purpose, Timing and
                                                Structure of the Merger; -
                                                Reasons for the Merger; -
                                                Opinion of Financial Advisor; -
                                                Perspective of NRG on the
                                                Fairness of the Merger

                                       7

<PAGE>   8



Item 8(b)...............................        SUMMARY - Recommendations of the
                                                Independent Directors Committee
                                                and the Board of Directors; -
                                                Opinion of CogenAmerica's
                                                Financial Advisor; SPECIAL
                                                FACTORS - Background of the
                                                Merger; - Purpose, Timing and
                                                Structure of the Merger; -
                                                Reasons for the Merger; -
                                                Opinion of Financial Advisor; -
                                                Perspective of NRG on the
                                                Fairness of the Merger

Item 8(c)...............................        SUMMARY - Record Date;
                                                Voting Power; Votes Required;
                                                THE SPECIAL MEETING - Record
                                                Date; Voting Power; Votes
                                                Required; SUMMARY OF MATERIAL
                                                FEATURES OF THE MERGER - The
                                                Merger - Conditions to the
                                                Merger

Item 8(d)...............................        SPECIAL FACTORS - Background of
                                                the Merger; - Recommendations of
                                                the Independent Directors
                                                Committee and the Board of
                                                Directors

Item 8(e)...............................        SUMMARY - Record Date;
                                                Voting Power; Votes Required;
                                                SPECIAL FACTORS - Background of
                                                the Merger; - Recommendations of
                                                the Independent Directors
                                                Committee and the Board of
                                                Directors; THE SPECIAL MEETING -
                                                Record Date; Voting Power;
                                                Votes Required; SUMMARY OF
                                                MATERIAL FEATURES OF THE MERGER
                                                - The Merger - Conditions to the
                                                Merger



                                       8


<PAGE>   9



Item 8(f)...............................        SPECIAL FACTORS - Background of
                                                the Merger; - Reasons for the
                                                Merger; - Recommendations of the
                                                Independent Directors Committee
                                                and the Board of Directors

Item 9(a)-(c)............................       SUMMARY - Opinion of
                                                CogenAmerica's Financial
                                                Advisor; - Recommendations of
                                                the Independent Directors
                                                Committee and the Board of
                                                Directors; SPECIAL FACTORS -
                                                Opinion of Financial Advisor

Item 10(a)...............................       SUMMARY - Record Date; Voting
                                                Power; Votes Required; THE
                                                SPECIAL MEETING - Record Date;
                                                Voting Power; Votes Required;
                                                INTEREST IN SECURITIES OF
                                                COGENAMERICA

Item 10(b)...............................       CERTAIN TRANSACTIONS IN COMMON
                                                STOCK AND STOCK OPTIONS

Item 11..................................       SUMMARY OF MATERIAL FEATURES OF
                                                THE MERGER; SUMMARY OF MATERIAL
                                                FEATURES OF THE CALPINE/NRG
                                                AGREEMENT

                                       9

<PAGE>   10


Item 12(a)-(b).........................         SUMMARY - Recommendations of the
                                                Independent Directors Committee
                                                and the Board of Directors; THE
                                                SPECIAL MEETING - Record Date;
                                                Voting Power; Votes Required;
                                                SPECIAL FACTORS - Reasons for
                                                the Merger; - Recommendations of
                                                the Independent Directors
                                                Committee and the Board of
                                                Directors; - Perspective of NRG
                                                on the Fairness of the Merger; -
                                                Conflicts of Interest; SUMMARY
                                                OF MATERIAL FEATURES OF THE
                                                CALPINE/NRG AGREEMENT

Item 13(a).............................         SUMMARY - Appraisal Rights;
                                                SUMMARY OF MATERIAL FEATURES OF
                                                THE MERGER - Appraisal Rights

Item 13(b)-(c).........................         Not applicable.


Item 14(a).............................         SELECTED CONSOLIDATED FINANCIAL
                                                DATA OF COGENAMERICA;
                                                INCORPORATION OF CERTAIN
                                                DOCUMENTS BY REFERENCE

Item 14(b).............................         Not applicable.

Item 15(a)-(b).........................         THE SPECIAL MEETING - General;
                                                EXPENSES OF THE TRANSACTION

Item 16................................         Not applicable.

Item 17(a).............................         Not applicable.

Item 17(b).............................         Fairness Opinion, dated as of
                                                August 26, 1999, delivered by
                                                Donaldson, Lufkin & Jenrette
                                                Securities Corporation (set
                                                forth as Appendix C to the Proxy
                                                Statement which is filed as
                                                Exhibit (d) hereto)*

Item 17(c)(1)..........................         Agreement and Plan of Merger
                                                among Cogeneration Corporation
                                                of America, Calpine Corporation
                                                and Calpine East Acquisition
                                                Corp., dated as of August 26,
                                                1999 (set forth as Appendix A to
                                                the Proxy Statement which is
                                                filed as Exhibit (d) hereto)*

Item 17(c)(2)..........................         Contribution and Stockholders
                                                Agreement, dated as of August
                                                26, 1999, among Calpine
                                                Corporation, Calpine East
                                                Acquisition Corp. and NRG
                                                Energy, Inc.

Item 17(d).............................         Copies of each of the
                                                Preliminary Proxy Statement of
                                                Cogeneration Corporation of
                                                America, Letter to Stockholders
                                                and Notice of Special Meeting of
                                                Stockholders

Item 17(e).............................         Section 262 of the Delaware
                                                General Corporation Law (set
                                                forth as Appendix D to the Proxy
                                                Statement which is filed as
                                                Exhibit (d) hereto)*

Item 17(f).............................         Not applicable.


* Incorporated by reference to the Proxy Statement

                                       10

<PAGE>   11





ITEM 1.        ISSUER AND CLASS OF SECURITY SUBJECT TO THE TRANSACTION.


       (a)     The information set forth on the Outside Front Cover Page and in
"QUESTIONS AND ANSWERS ABOUT THE MERGER" and "SUMMARY - The Companies" of the
Proxy Statement is incorporated herein by reference.

       (b)     The information set forth in "SUMMARY - The Special Meeting" and
"THE SPECIAL MEETING - Record Date; Voting Power; Votes Required" of the Proxy
Statement is incorporated herein by reference.

       (c)     The information set forth in "HISTORICAL MARKET INFORMATION" of
the Proxy Statement is incorporated herein by reference.

       (d)     The information set forth in "HISTORICAL MARKET INFORMATION" of
the Proxy Statement is incorporated herein by reference.

       (e)     Not applicable.

       (f)     On April 30, 1996, NRG received an option to convert $3,000,000
of the outstanding principal amount of the loan then existing between NRG and
O'Brien (Schuylkill) Cogeneration, Inc. ("Schuylkill") into 396,255 shares of
common stock of CogenAmerica. Such option vested on August 22, 1997 when NRG
loaned additional funds to Schuylkill. On Novermber 25, 1997, NRG converted
$3,000,000 of the loan balance into 396,255 shares at a per share price of
approximately $7.57. The average price of CogenAmerica's common stock was $16.40
and $19.48, respectively, for the third and fourth quarters of 1997.


ITEM 2.        IDENTITY AND BACKGROUND.

               This Statement is being filed jointly by NRG and CogenAmerica
(the "Filing Persons"). The information set forth on the Outside Front Cover
Page and in "SUMMARY - The Companies" of the Proxy Statement is incorporated
herein by reference.


       (a)-(d) Not applicable.

                                       11

<PAGE>   12


       (e)     During the last five years, none of the Filing Persons nor, to
the best of their respective knowledge, any of their directors, executive
officers or controlling persons have been convicted in a criminal proceeding
(excluding traffic violations or similar misdemeanors).

       (f)     During the last five years, none of the Filing Persons nor, to
the best of their respective knowledge, any of their directors, executive
officers or controlling persons was a party to a civil proceeding of a judicial
or administrative body of competent jurisdiction and as a result of such
proceeding was or is subject to a judgment, decree or final order enjoining
further violations of, or prohibiting activities, subject to, federal or state
securities laws or finding any violation of such laws.

       (g)     Not applicable.

ITEM 3.        PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS.

       (a)(1)  The information set forth on the Outside Front Cover Page and in
"SPECIAL FACTORS - Background of the Merger"; "- Reasons for the Merger";
"- Conflicts of Interest - Arrangements with NRG" of the Proxy Statement is
incorporated herein by reference.

       (a)(2) and (b)   The information set forth on the Outside Front Cover
Page and in "SUMMARY - Recommendations of the Independent Directors Committee
and the Board of Directors"; and "SPECIAL FACTORS - Background of the Merger";
"- Reasons for the Merger"; "- Conflicts of Interest - Arrangements with NRG" of
the Proxy Statement is incorporated herein by reference.

               In addition, on September 14, 1998, NRG sent a letter to
CogenAmerica's Chairman requesting that he call a special meeting of
CogenAmerica's stockholders to consider removal of Robert Sherman from
CogenAmerica's Board of Directors. NRG also filed definitive solicitation
materials with the Securities and Exchange Commission pursuant to Section 14(a)
of the Securities and Exchange Act of 1934, as amended, relating to a proposed
solicitation of proxies and consents from CogenAmerica's stockholders to remove
Mr. Sherman from CogenAmerica's Board of Directors. On October 26, 1998,
consents of over


                                       12


<PAGE>   13


50% of CogenAmerica's stockholders in favor of Mr. Sherman's removal from
CogenAmerica's Board of Directors were filed with CogenAmerica and Mr. Sherman
was removed from CogenAmerica's Board of Directors.


ITEM 4.        TERMS OF THE TRANSACTION.

       (a)     The information set forth in "QUESTIONS AND ANSWERS ABOUT THE
MERGER"; "SUMMARY - Terms of the Merger Agreement"; "SPECIAL FACTORS - Purpose,
Timing and Structure of the Merger"; and "SUMMARY OF MATERIAL FEATURES OF THE
MERGER" of the Proxy Statement is incorporated herein by reference.

       (b)     The information set forth in "QUESTIONS AND ANSWERS ABOUT THE
MERGER"; "SUMMARY - Terms of the Merger Agreement"; "SPECIAL FACTORS - Purpose,
Timing and Structure of the Merger"; "SUMMARY OF MATERIAL FEATURES OF THE
MERGER"; and "SUMMARY OF MATERIAL FEATURES OF THE CALPINE/NRG AGREEMENT" of the
Proxy Statement is incorporated herein by reference.


ITEM 5.        PLANS OR PROPOSALS OF THE ISSUER OR AFFILIATE.

       (a) - (b)   The information set forth in "SUMMARY - Terms of the Merger
Agreement"; "SPECIAL FACTORS - Background of the Merger"; " - Plans for
CogenAmerica After the Merger"; "- Conflicts of Interest - Arrangements with
NRG"; "SUMMARY OF MATERIAL FEATURES OF THE MERGER"; and "SUMMARY OF MATERIAL
FEATURES OF THE CALPINE/NRG AGREEMENT" of the Proxy Statement is incorporated
herein by reference.

       (c) - (d)   The information set forth in "SUMMARY - Terms of the Merger
Agreement"; "SPECIAL FACTORS - Purpose, Timing and Structure of the Merger"; " -
Plans for CogenAmerica After the Merger"; and "SUMMARY OF MATERIAL FEATURES OF
THE MERGER"; "SUMMARY OF MATERIAL FEATURES OF THE CALPINE/NRG AGREEMENT" of the
Proxy Statement is incorporated herein by reference.

       (e)     The information set forth in "QUESTIONS AND ANSWERS ABOUT THE
MERGER"; "SUMMARY - Terms of the Merger Agreement"; "SPECIAL FACTORS - Purpose,
Timing and Structure of the Merger"; " - Plans for CogenAmerica After the
Merger"; "SUMMARY OF MATERIAL FEATURES OF THE MERGER"; and "SUMMARY OF



                                       13

<PAGE>   14


MATERIAL FEATURES OF THE CALPINE/NRG AGREEMENT"; of the Proxy Statement is
incorporated herein by reference.

       (f) - (g)   The information set forth in "QUESTIONS AND ANSWERS ABOUT THE
MERGER"; "SUMMARY - Terms of the Merger Agreement"; "SPECIAL FACTORS - Purpose,
Timing and Structure of the Merger"; "SUMMARY OF MATERIAL FEATURES OF THE
MERGER"; and "SPECIAL FACTORS - Certain Effects of the Merger" of the Proxy
Statement is incorporated herein by reference.

ITEM 6.        SOURCE AND AMOUNTS OF FUNDS OR OTHER CONSIDERATION.

       (a) and (d) The information set forth in "SUMMARY OF MATERIAL FEATURES
OF THE MERGER - Financing of the Merger; Source of Funds" of the Proxy Statement
is incorporated herein by reference.

       (b)     The information set forth in "EXPENSES OF THE TRANSACTION" of the
Proxy Statement is incorporated herein by reference.

       (c )    Not applicable.

ITEM 7.        PURPOSE(S), ALTERNATIVES, REASONS AND EFFECTS.

       (a) - (c)   The information set forth in "SUMMARY - Potential Benefits
and Detriments of the Merger to Unaffiliated Stockholders; Benefits to
Insiders"; and "SPECIAL FACTORS - Background of the Merger"; "- Purpose, Timing
and Structure of the Merger"; "- Reasons for the Merger"; "- Perspective of NRG
on the Fairness of the Merger" of the Proxy Statement is incorporated herein by
reference.

       (d)     The information set forth in "SUMMARY - Potential Benefits and
Detriments of the Merger to Unaffiliated Stockholders; Benefits to Insiders";
"SPECIAL FACTORS - Background of the Merger"; "- Purpose, Timing and Structure
of the Merger"; "- Reasons for the Merger"; "- Perspective of NRG on the
Fairness of the Merger"; and "SUMMARY OF MATERIAL FEATURES OF THE MERGER -
Federal



                                       14


<PAGE>   15

Income Tax Consequences of the Transaction" of the Proxy Statement is
incorporated herein by reference.


ITEM 8.        FAIRNESS OF THE TRANSACTION.

       (a)     The information set forth in "QUESTIONS AND ANSWERS ABOUT THE
MERGER"; "SUMMARY - Recommendations of the Independent Directors Committee and
the Board of Directors"; "- Opinion of CogenAmerica's Financial Advisor"; and
"SPECIAL FACTORS - Background of the Merger"; "- Purpose, Timing and Structure
of the Merger"; "- Reasons for the Merger"; "- Opinion of Financial Advisor";
"- Perspective of NRG on the Fairness of the Merger" of the Proxy Statement is
incorporated herein by reference.

       (b)     The information set forth in "SUMMARY - Recommendations of the
Independent Directors Committee and the Board of Directors"; "- Opinion of
CogenAmerica's Financial Advisor"; and "SPECIAL FACTORS - Background of the
Merger"; "- Purpose, Timing and Structure of the Merger"; "- Reasons for the
Merger"; "- Opinion of Financial Advisor"; "- Perspective of NRG on the Fairness
of the Merger" of the Proxy Statement is incorporated herein by reference.

       (c)     The information set forth in "SUMMARY - Record Date; Voting
Power; Votes Required"; "THE SPECIAL MEETING - Record Date; Voting Power;
Votes Required" and "SUMMARY OF MATERIAL FEATURES OF THE MERGER - The Merger -
Conditions to the Merger" of the Proxy Statement is incorporated herein by
reference.

       (d)     The information set forth in "SPECIAL FACTORS - Background of the
Merger"; "- Recommendations of the Independent Directors Committee and the
Board of Directors" of the Proxy Statement is incorporated herein by reference.

       (e)     The information set forth in "SUMMARY - Record Date; Voting
Power; Votes Required"; "SPECIAL FACTORS - Background of the Merger"; "-
Recommendations of the Independent Directors Committee and the Board of
Directors"; "THE SPECIAL MEETING - Record Date; Voting Power;
Votes Required" and "SUMMARY OF MATERIAL FEATURES OF THE MERGER - The Merger -
Conditions to the Merger" of the Proxy Statement is incorporated herein by
reference.

       (f)     The information set forth in "SPECIAL FACTORS - Background of the
Merger"; "- Reasons for the Merger"; "- Recommendations of the Independent


                                       15


<PAGE>   16


Directors Committee and the Board of Directors" of the Proxy Statement is
incorporated herein by reference.


ITEM 9.        REPORTS, OPINIONS, APPRAISALS AND CERTAIN NEGOTIATIONS.

       (a) - (c)   The information set forth in "SUMMARY - Opinion of
CogenAmerica's Financial Advisor"; "- Recommendations of the Independent
Directors Committee and the Board of Directors"; and "SPECIAL FACTORS - Opinion
of Financial Advisor" of the Proxy Statement is incorporated herein by
reference.


ITEM 10.       INTEREST IN SECURITIES OF THE ISSUER.

       (a)     The information set forth in "SUMMARY - Record Date; Voting
Power; Votes Required"; "THE SPECIAL MEETING - Record Date; Voting Power; Votes
Required" and "INTEREST IN SECURITIES OF COGENAMERICA" of the Proxy Statement is
incorporated herein by reference.

       (b)     The information set forth in "CERTAIN TRANSACTIONS IN COMMON
STOCK AND STOCK OPTIONS" of the Proxy Statement is incorporated herein by
reference.


ITEM 11.       CONTRACTS, ARRANGEMENTS OR UNDERSTANDINGS WITH RESPECT TO THE
               ISSUER'S SECURITIES.

       The information set forth in "SUMMARY OF MATERIAL FEATURES OF THE
MERGER"; and "SUMMARY OF MATERIAL FEATURES OF THE CALPINE/NRG AGREEMENT" of the
Proxy Statement is incorporated herein by reference.


ITEM 12.       PRESENT INTENTION AND RECOMMENDATION OF CERTAIN PERSONS WITH
               REGARDS TO THE TRANSACTION.

       (a)-(b)     The information set forth in "SUMMARY - Recommendations of
the Independent Directors Committee and the Board of Directors"; "THE SPECIAL
MEETING - Record Date; Voting Power; Votes Required"; "SPECIAL FACTORS - Reasons
for the Merger"; "- Recommendations of the Independent Directors Committee and
the Board of Directors"; "- Perspective of NRG on the Fairness of the


                                       16


<PAGE>   17


Merger"; "- Conflicts of Interest"; and "SUMMARY OF MATERIAL FEATURES OF THE
CALPINE/NRG AGREEMENT" of the Proxy Statement is incorporated herein by
reference.


ITEM 13.       OTHER PROVISIONS OF THE TRANSACTION.

       (a)     The information set forth in "SUMMARY - Appraisal Rights"; and
"SUMMARY OF MATERIAL FEATURES OF THE MERGER - Appraisal Rights" of the Proxy
Statement is incorporated herein by reference.

       (b)-(c) Not Applicable.


ITEM 14.       FINANCIAL INFORMATION.

       (a)     The information set forth in "SELECTED CONSOLIDATED FINANCIAL
DATA OF COGENAMERICA"; and "INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE" of
the Proxy Statement is incorporated herein by reference.

       (b)     Not Applicable.


ITEM 15.       PERSONS AND ASSETS EMPLOYED, RETAINED OR UTILIZED.

       (a)-(b) The information set forth in "THE SPECIAL MEETING - General";
and "EXPENSES OF THE TRANSACTION" of the Proxy Statement is incorporated herein
by reference.


ITEM 16.       ADDITIONAL INFORMATION.

       Not Applicable.


ITEM 17.       MATERIAL TO BE FILED AS EXHIBITS.

       (a)     Not Applicable.

       (b)     Fairness Opinion, dated as of August 26, 1999, delivered by
Donaldson, Lufkin & Jenrette Securities Corporation (set forth as Appendix C to
the Proxy Statement which is filed as Exhibit (d) hereto)*


                                       17

<PAGE>   18


       (c)(1)  Agreement and Plan of Merger among Cogeneration Corporation of
America, Calpine Corporation and Calpine East Acquisition Corp., dated August
26, 1999 (set forth as Appendix A to the Proxy Statement which is filed as
Exhibit (d) hereto)*

       (c)(2)  Contribution and Stockholders Agreement, dated as of August 26,
1999, among Calpine Corporation, Calpine East Acquisition Corp. and NRG Energy,
Inc.

       (d)     Copies of each of the Preliminary Proxy Statement of Cogeneration
Corporation of America, Letter to Stockholders and Notice of Special Meeting of
Stockholders, filed with the SEC on September 24, 1999

       (e)     Section 262 of the Delaware General Corporation Law (set forth
as Appendix D to the Proxy Statement which is filed as Exhibit (d) hereto)*

       (f)     As of the date of this Statement, no written instruction, form or
other material has been furnished to any person making the actual oral
solicitation or other recommendation (including the proxy solicitor referred to
in "THE SPECIAL MEETING - Voting Procedures; Proxies" of the Proxy Statement)
for such person's use, directly or indirectly in connection with the Rule 13e-3
transaction.




*Incorporated by reference to the Proxy Statement


                                       18

<PAGE>   19


                                   SIGNATURES

         After due inquiry and to the best of our knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated:  September 23, 1999


                                      NRG ENERGY, INC.



                                      By: /s/ James J. Bender
                                         -------------------------------------
                                      Name: James J. Bender
                                      Title: Vice President and General Counsel



                                       19

<PAGE>   20



                                   SIGNATURES

         After due inquiry and to the best of our knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Dated:  September 23, 1999


                                       COGENERATION CORPORATION OF
                                       AMERICA



                                       By: /s/ Julie A. Jorgensen
                                          ------------------------------------
                                       Name: Julie A. Jorgensen
                                       Title: President and Chief
                                              Executive Officer



                                       20

<PAGE>   21


                                  EXHIBIT INDEX

        EXHIBIT                                          DESCRIPTION

99(c)(2)                                Contribution and Stockholders Agreement,
                                        dated as of August 26, 1999, among
                                        Calpine Corporation, Calpine East
                                        Acquisition Corp. and NRG Energy, Inc.

99(d)                                   Copies of each of the Preliminary Proxy
                                        Statement of Cogeneration Corporation of
                                        America, Letter to Stockholders and
                                        Notice of Special Meeting of
                                        Stockholders






                                       21






<PAGE>   1
                                                                  EXHIBIT (c)(2)


                                CONTRIBUTION AND
                             STOCKHOLDERS AGREEMENT



     CONTRIBUTION AND STOCKHOLDERS AGREEMENT (this "Agreement"), dated as of
August 26, 1999, among CALPINE EAST ACQUISITION CORP., a Delaware corporation
(the "Company"), CALPINE CORPORATION, a Delaware corporation ("Buyer"), and NRG
ENERGY, INC., a Delaware corporation ("NRG", and together with the Buyer, the
"Stockholders").

                              W I T N E S S E T H:

     WHEREAS, on the date hereof, the Company is authorized by its Certificate
of Incorporation to issue Capital Stock consisting of 1,000 shares of common
stock, without par value (the "Common Stock");

     WHEREAS, the Company has been formed for the purpose of entering into an
Agreement and Plan of Merger, dated as of the date hereof (the "Merger
Agreement"), and, subject to satisfaction or waiver of the conditions set forth
in the Merger Agreement, consummating a merger (the "Merger") with and into
Cogeneration Corporation of America, a Delaware corporation ("Cogen"), with
Cogen continuing as the surviving corporation;

     WHEREAS, it is contemplated that immediately prior to and following the
consummation of the Merger, NRG will own 20% of the issued and outstanding
shares of Capital Stock of the Company and the Buyer will own 80% of the issued
and outstanding shares of Capital Stock of the Company; and

     WHEREAS, the parties hereto deem it in their best interests and in the best
interests of the Company to provide consistent and uniform management for the
Company and desire to enter into this Agreement in order to effectuate that
purpose and to set forth their respective rights and obligations in connection
with their proposed investment in the Company.

     NOW, THEREFORE, in consideration of the mutual agreements and
understandings set forth herein, the parties hereto, intending to be legally
bound, hereby agree as follows:





<PAGE>   2




                                    ARTICLE I

                                   DEFINITIONS

     Section 1.1.   Certain Definitions. As used in this Agreement, the
following terms shall have the following respective meanings:

     "Actual Adjusted Net Income" has the meaning specified in Section 9.3(a).

     "Adjustment Amount" has the meaning specified in Section 5.1(a).

     "Affiliate" has the meaning set forth in Rule 12b-2 of the General Rules
and Regulations under the Exchange Act.

     "Agreement" means this Contribution and Stockholders Agreement as in effect
on the date hereof and as hereafter from time to time amended, modified or
supplemented in accordance with the terms hereof.

     "Bankruptcy Code" means the United States Bankruptcy Code, 11 U.S.C. Sec.
101 et seq., as now in effect and as from time to time hereafter amended, and
any successor or similar statute.

     "Board of Directors" means the Board of Directors of the Company as from
time to time hereafter constituted.

     "Buyer Directors" has the meaning specified in Section 2.3(b).

     "By-Laws" means the Amended and Restated By-Laws of the Company in the form
set forth as Exhibit D hereto, and as hereafter from time to time amended,
modified, supplemented or restated in accordance with the terms hereof and
pursuant to applicable law.

     "Cancelled Options" has the meaning specified in Section 5.1(a).

     "Capital Stock" means and includes (i) any and all shares, interests,
participations or other equivalents of or interests in (however designated)
corporate stock of any Person, including, without limitation, shares of
preferred or preference stock, (ii) all partnership interests (whether general
or limited) in any Person which is a partnership, (iii) all membership interests
or limited liability company interests in any Person which is a limited
liability company, and (iv) all equity or ownership interests in any Person of
any other type.


                                        2

<PAGE>   3



     "Cash Equivalents" means

     (a) marketable obligations maturing within 180 days after acquisition
thereof issued or fully guaranteed by the United States of America or an
instrumentality or agency thereof,

     (b) open market commercial paper, maturing within 180 days after
acquisition thereof, which has the highest credit rating of either Standard &
Poor's Corporation or Moody's Investors Service, Inc., issued by a corporation
(other than the Company or any of its Subsidiaries or Affiliates) organized
under the laws of any State of the United States of America or of the District
of Columbia, and

     (c) certificates of deposit or bankers acceptances or other obligations
maturing within 180 days after acquisition thereof issued by a domestic
commercial bank which is a member of the Federal Reserve System and has capital,
surplus and undivided profits in excess of $500,000,000.

     "Certificate of Incorporation" means the Amended and Restated Certificate
of Incorporation of the Company in the form set forth as Exhibit C hereto, and
as hereafter from time to time amended, modified, supplemented or restated in
accordance with the terms hereof and pursuant to applicable law.

     "Cogen" has the meaning specified in the Recitals.

     "Commission" means the Securities and Exchange Commission and any successor
commission or agency having similar powers.

     "Common Stock" means the common stock, without par value, of the Company
and any Capital Stock of the Company that is not limited to a fixed sum or
percentage of par or stated value in respect to the rights of the holders
thereof to participate in dividends or in the distribution of assets upon any
liquidation, dissolution or winding up of the Company.

     "Company" has the meaning specified in the first paragraph of this
Agreement, together with any of its successors or assigns (including, without
limitation, Cogen following the consummation of the Merger).

     "Company Sale" has the meaning specified in Section 8.2(a).

     "Contribution Date" has the meaning specified in Section 5.1.

     "Drag-Along Notice" has the meaning specified in Section 8.2(a).


                                        3

<PAGE>   4



     "Drag Along Right" has the meaning specified in Section 8.2(b).

     "Disposing Stockholder" has the meaning specified in Section 8.3(b).

     "Effective Date" means the date on which the Effective Time (as such term
is defined in the Merger Agreement) occurs.

     "Exchange Act" means, as of any date, the Securities Exchange Act of 1934,
as amended.

     "Fully Diluted Common Stock" means at any time all shares of Common Stock
then issued and outstanding and all shares of Common Stock issuable upon the
exercise of any then outstanding warrants, options, conversion rights or other
rights to subscribe for, purchase or acquire shares of Common Stock that are at
the time exercisable.

     "GAAP" means generally accepted accounting principles in the United States
of America in effect from time to time, applied on a consistent basis both as to
classification of items and amounts.

     "HSR Act" means the Hart-Scott-Rodino Antitrust Improvements Act of 1976,
as amended.

     "Independent Third Party" has the meaning specified in Section 8.2(a).

     "Management Fee" has the meaning specified in Section 9.3(a).

     "Merger" has the meaning specified in the Recitals.

     "Merger Agreement" has the meaning specified in the Recitals.

     "Merger Price" has the meaning specified in Section 5.1(a).

     "NASD" means the National Association of Securities Dealers, Inc. and its
successors and assigns.

     "Notice of Exercise" has the meaning specified in Section 8.1(a).

     "NRG Director" has the meaning specified in Section 2.3(b).

     "Offered Securities" has the meaning specified in Section 8.1(a).

     "Option" has the meaning specified in Section 8.4(a).

                                        4

<PAGE>   5




     "Option Period" has the meaning specified in Section 8.4(a).

     "Option Price" has the meaning specified in Section 8.4(b).

     "Permitted Transferee" has the meaning specified in Section 7.2.

     "Person" means an individual or a corporation, association, partnership,
limited liability company, joint venture, organization, business, trust or any
other entity or organization, including a government or any subdivision or
agency thereof.

     "Pro Rata Portion" means, with reference to any Stockholder at any time, a
fraction, the numerator of which is the number of shares of Common Stock then
issued and outstanding and held by such Stockholder, and the denominator of
which is the aggregate number of shares of Common Stock then issued and
outstanding and held by the Stockholders taken together.

     "Projected Adjusted Net Income" has the meaning set forth in Section
9.3(a).

     "Proposed Purchaser" has the meaning specified in Section 8.3(b).

     "Public Offering" means a public offering and sale of equity securities of
the Company pursuant to an effective registration statement under the Securities
Act.

     "Purchase Offer" has the meaning specified in Section 8.3(b).

     "Quorum of the Board" has the meaning specified in Section 2.3(d).

     "Registrable Securities" means the following: (a) all shares of Common
Stock issued or issuable now or hereafter owned of record or beneficially by any
Stockholder and (b) any shares of Capital Stock issued or issuable by the
Company in respect of any shares of Common Stock referred to in the foregoing
clause (a) by way of a stock dividend or stock split or in connection with a
combination or subdivision of shares, reclassification, recapitalization,
merger, consolidation or other reorganization of the Company.

     As to any particular Registrable Securities that have been issued, such
securities shall cease to be Registrable Securities when (i) a registration
statement with respect to the sale of such securities shall have become
effective under the Securities Act and such securities shall have been disposed
of under such registration statement, (ii) they shall have been distributed to
the public pursuant to Rule 144 under the Exchange Act, (iii) they shall have
been otherwise transferred or disposed of, and new certificates

                                        5

<PAGE>   6



therefor not bearing a legend restricting further transfer shall have been
delivered by the Company, and subsequent transfer or disposition of them shall
not require their registration or qualification under the Securities Act or any
similar state law then in force, (iv) they shall have ceased to be outstanding,
or (v) with respect to the Registrable Securities held by any Person, when such
Registrable Securities, when aggregated with the Registrable Securities held by
such Person's Affiliates, constitute 1% or less of the shares of Common Stock at
the time outstanding.

     "Registration Expenses" means any and all out-of-pocket expenses incident
to the Company's performance of or compliance with Section 10 hereof, including,
without limitation, all Commission, stock exchange and NASD registration and
filing fees, all fees and expenses of complying with securities and blue sky
laws (including the reasonable fees and disbursements of underwriters' counsel
in connection with blue sky qualifications and NASD filings), all fees and
expenses of the transfer agent and registrar for the Registrable Securities, all
printing expenses, the fees and disbursements of counsel for the Company and of
its independent public accountants, including the expenses of any special audits
or "cold comfort" letters required by or incident to such performance and
compliance, but excluding underwriting discounts and commissions and applicable
transfer and documentary stamp taxes, if any, which shall be borne by the seller
of the securities in all cases.

     "Restricted Period" means the three-year period commencing on the Effective
Date.

     "Securities Act" means, as of any date, the Securities Act of 1933, as
amended.

     "Stockholder" means (i) the Buyer, (ii) NRG or (iii) each Permitted
Transferee of any such Person who becomes a party to or bound by the provisions
of this Agreement in accordance with the terms hereof.

     "Subsidiary" means as to any Person a corporation of which outstanding
shares of Common Stock having the power to elect a majority of the Board of
Directors of such corporation are at the time owned, directly or indirectly
through one or more intermediaries, or both, by such Person.

     "Total Equity Value of the Company" has the meaning specified in Section
5.1(a).

     "Transfer" has the meaning specified in Section 7.1.

     "Transfer Notice" has the meaning specified in Section 8.1(a).


                                        6

<PAGE>   7



     "Transfer Offer" has the meaning specified in Section 8.1(a).

     "Transfer Offer Price Per Security" shall have the meaning specified in
Section 8.1(a).

     "Valuation Notice" has the meaning specified in Section 8.4(b).

     "Valuing Investment Bank" has the meaning specified in Section 8.4(b).

     "Wholly-Owned Subsidiary" means, with respect to any Person, any Subsidiary
of such Person all of the Capital Stock (and all options, warrants, conversion
rights and other rights to subscribe for, purchase or acquire such Capital
Stock) of which, other than directors' qualifying shares, are owned,
beneficially and of record, by such Person or one or more Wholly-Owned
Subsidiaries of such Person.


                                   ARTICLE II

                                   THE COMPANY

     Section 2.1 Organizational Documents. Attached hereto as Exhibits A and B,
respectively, are the current certificate of incorporation and by-laws of the
Company. On the Contribution Date but prior to the making of the contributions
referred to in Section 5.1 hereof, the Buyer and the Company shall cause the
Amended and Restated Certificate of Incorporation of the Company in the form set
forth as Exhibit C hereto to be filed with the Secretary of State of the State
of Delaware, and the Amended and Restated By-Laws of the Company in the form set
forth as Exhibit D hereto shall be approved by the Board of Directors.

     Section 2.2 Capitalization. Prior to the Contribution Date, the
capitalization of the Company shall be 1,000 shares of Common Stock, all of
which shall be held by the Buyer.

     Section 2.3 Board of Directors. The following provisions shall apply with
respect to the Board of Directors of the Company commencing on the Contribution
Date:

          (a) Conduct of Business. The parties hereto confirm that it is their
     intention that the business and affairs of the Company shall be managed by
     its Board of Directors in the best interests of the Company.

          (b) Board of Directors. The Board of Directors shall be composed of no
     more than seven directors. Each Stockholder agrees to

                                        7

<PAGE>   8



     vote its shares of Common Stock, whether at a duly-convened meeting or by
     written consent, to elect no more than seven directors, one of whom shall
     be nominated by NRG (the "NRG Director") and the remainder of whom shall be
     nominated by the Buyer (the "Buyer Directors").

          (c) Removal; Vacancies. Any director may be removed from the Board of
     Directors, with or without cause, only upon the affirmative vote of the
     Stockholders and in accordance with the terms of this Section 2.3(c). The
     NRG Director shall not be removed, with or without cause, without the prior
     written consent of NRG. NRG agrees to vote all of its shares of Common
     Stock for the removal of a Buyer Director upon the request of the Buyer,
     and agrees not to vote any of its shares of Common Stock for the removal of
     any Buyer Director under any other circumstance. The Buyer agrees to vote
     all of its shares of Common Stock for the removal of the NRG Director upon
     the request of NRG, and agrees not to vote any of its shares of Common
     Stock of the Company for the removal of the NRG Director under any other
     circumstance. In the event that any Director is unwilling or unable (by
     reason of death, resignation or otherwise) to serve as such or is removed
     in accordance with the terms of this Section 2.3(c), then the Stockholders
     shall promptly elect the successor or replacement to such Director upon the
     nomination of the Stockholder which appointed such Director.

          (d) Quorum of the Board of Directors. A quorum for any meeting of the
     Board of Directors shall be at least a majority of the directors (a "Quorum
     of the Board"); provided, that at least 48 hours prior written notice of
     such meeting is duly given to the NRG Director. No action may be taken by
     the Board of Directors at any meeting unless a Quorum of the Board is
     present at the time such action is taken.

          (e) Committees of the Board of Directors. The Board of Directors shall
     not have any committees, unless approved by the unanimous consent of all
     members of the Board of Directors or unless the NRG Director is a member of
     such committee.

     Section 2.4 No Conflict with Agreement. Each Stockholder shall vote its
shares of Common Stock, and shall take all actions necessary, to ensure that the
Certificate of Incorporation and By-Laws do not, at any time, conflict with the
provisions of this Agreement. In the event of any conflict between this
Agreement and the Certificate of Incorporation or the By-Laws, the provisions
of this Agreement shall govern and the Company and the Stockholders shall take
action as is required to ensure that the Certificate of Incorporation and the
By-Laws do not conflict with this Agreement.


                                        8

<PAGE>   9




                                   ARTICLE III

                         REPRESENTATIONS AND WARRANTIES

               Section 3.1 Representations and Warranties of NRG.

          (a) Organization. NRG is a corporation duly incorporated, validly
     existing and in good standing under the laws of the State of Delaware and
     is duly licensed or qualified to transact business as a foreign corporation
     and is in good standing in each jurisdiction in which the nature of the
     business transacted by it or the character of the properties owned or
     leased by it requires such licensing or qualification.

          (b) Due Authorization; Non-Contravention. The execution and delivery
     by NRG of this Agreement and the performance by NRG of its obligations
     hereunder have been duly authorized by all requisite corporate action and
     will not violate any provision (x) of the Certificate of Incorporation of
     NRG, as amended, or the By-laws of NRG, as amended, (y) of law, any order
     of any court or other agency of government, or (z) of any indenture,
     agreement or other instrument to which NRG or any of its properties or
     assets is bound, or conflict with, result in a breach of or constitute
     (with due notice or lapse of time or both) a default under any such
     indenture, agreement or other instrument, or result in the creation or
     imposition of any lien, charge, restriction, claim or encumbrance of any
     nature whatsoever upon any of the properties or assets of NRG, it being
     understood that, in connection with the transactions contemplated by this
     Agreement and the Merger Agreement, the parties will make all requisite
     filings and otherwise comply with the applicable requirements of (i) the
     HSR Act, (ii) the Exchange Act and the Securities Act, (iii) state
     securities, takeover or blue sky laws, and (iv) any other laws or
     regulations.

          (c) Binding Agreement. This Agreement has been duly executed and
     delivered by NRG and, assuming the due execution and delivery by the other
     parties hereto, constitutes the legal, valid and binding obligation of NRG
     enforceable in accordance with its terms.

          (d) Ownership of Shares. NRG (or accounts controlled or beneficially
     owned by NRG) is the lawful owner of 3,106,612 shares of common stock of
     Cogen, and has the power to vote and dispose of such shares. To NRG's
     knowledge, such shares of common stock are validly issued, fully paid and
     nonassessable, with no personal liability attaching to

                                        9

<PAGE>   10



     the ownership thereof. NRG has good title to its shares of common stock,
     free and clear of any liens, adverse claims or encumbrances whatsoever with
     respect to the ownership of or the right to vote such shares. Such shares
     constitute all of the shares of common stock of Cogen owned of record or
     beneficially by NRG. NRG does not own any options to purchase or rights to
     subscribe for or otherwise acquire any securities of Cogen. Except as
     otherwise provided in this Agreement, NRG has the sole voting power and
     sole power to issue instructions with respect to the matters set forth in
     this Agreement, sole power of disposition, sole power to demand appraisal
     rights and sole power to agree to all of the matters set forth in this
     Agreement, in each case with respect to all of the shares of common stock
     of Cogen owned by NRG with no limitations, qualifications or restrictions
     on such rights, subject to applicable securities laws and the terms of this
     Agreement. The terms "beneficially own" or "beneficial ownership" with
     respect to any securities shall mean having "beneficial ownership" of such
     securities as determined pursuant to Rule 13d-3 under the Exchange Act.

     Section 3.2 Representations and Warranties of the Buyer.

          (a) Organization. The Buyer is a corporation duly incorporated,
     validly existing and in good standing under the laws of the State of
     Delaware and is duly licensed or qualified to transact business as a
     foreign corporation and is in good standing in each jurisdiction in which
     the nature of the business transacted by it or the character of the
     properties owned or leased by it requires such licensing or qualification.

          (b) Due Authorization; Non Contravention. The execution and delivery
     by the Buyer of this Agreement and the performance by the Buyer of its
     obligations hereunder have been duly authorized by all requisite corporate
     action and will not violate any provision (x) of the Certificate of
     Incorporation of the Buyer, as amended or the By-laws of the Buyer, as
     amended, (y) of law, any order of any court or other agency of government,
     or (z) of any indenture, agreement or other instrument to which the Buyer
     or any of its properties or assets is bound, or conflict with, result in a
     breach of or constitute (with due notice or lapse of time or both) a
     default under any such indenture, agreement or other instrument, or result
     in the creation or imposition of any lien, charge, restriction, claim or
     encumbrance of any nature whatsoever upon any of the properties or assets
     of the Buyer, it being understood that, in connection with the transactions
     contemplated by this Agreement and the Merger Agreement, the parties will
     make all requisite filings and otherwise comply with the applicable
     requirements of (i) the HSR Act, (ii) the Exchange Act and the

                                       10

<PAGE>   11



     Securities Act, (iii) state securities, takeover or blue sky laws, and (iv)
     any other laws or regulations.

          (c) Binding Agreement. This Agreement has been duly executed and
     delivered by the Buyer and, assuming the due execution and delivery by the
     other parties hereto, constitutes the legal, valid and binding obligation
     of the Buyer enforceable in accordance with its terms.


                                   ARTICLE IV

                                    COVENANTS


     Section 4.1 Irrevocable Proxy. NRG hereby irrevocably appoints the Buyer,
or any designee of the Buyer, with full power of substitution the lawful agent,
attorney and proxy of NRG, from the date hereof until the Effective Date or
unless this Agreement is terminated pursuant to Article XI hereof, at any
meeting of the stockholders of Cogen, however called, or in connection with any
written consent of the stockholders of Cogen (including the right to sign its
name (as a stockholder) to any consent, certificate or other document relating
to Cogen that the law of the State of Delaware may permit or require), to vote
(or cause to be voted) the shares of common stock of Cogen held of record or
beneficially by NRG (i) in favor of the Merger, the execution and delivery by
Cogen of the Merger Agreement and any amendments thereto (so long as any such
amendment does not materially adversely affect NRG) and the approval of the
terms thereof, the amendment of the Cogen certificate of incorporation as
provided in the Merger Agreement, and each of the other actions contemplated by
this Agreement and the Merger Agreement, and any amendments hereto or thereto,
with NRG's consent pursuant to the terms of this Agreement, and any actions
required in furtherance hereof and thereof, (ii) against any proposal for any
recapitalization, merger, sale of assets or other business combination between
Cogen and any Person (other than the Merger) or any other action or agreement
that would result in a breach of any covenant, representation or warranty or any
other obligation or agreement of Cogen under the Merger Agreement or this
Agreement, (iii) against any of the following actions (other than the
transactions contemplated by the Merger Agreement): (1) any extraordinary
corporate transaction, such as a merger, consolidation or other business
combination involving Cogen or any of its Subsidiaries; (2) a sale, lease or
transfer of a material amount of assets of Cogen or any of its Subsidiaries or a
reorganization, recapitalization, dissolution or liquidation of Cogen of any of
its Subsidiaries; (3) (a) any change in the majority of Cogen's board of
directors; (b) any material change in the present capitalization of Cogen or any
amendment to Cogen's certificate of incorporation (other than such amendment
contemplated in connection with the Merger); or (c) any other change in Cogen's
corporate structure or business; or (4) any other action which, is intended, or
could reasonably be expected, to impede, interfere with, delay, postpone,
discourage or


                                       11

<PAGE>   12



adversely affect the Merger or the transactions contemplated by this Agreement
or the contemplated economic benefits of any of the foregoing, or impede,
interfere with, delay, postpone, discourage or adversely affect the Merger or
the transactions contemplated by this Agreement. NRG further agrees to cause its
shares of common stock of Cogen that are outstanding and owned by it
beneficially to be voted in accordance with the foregoing. NRG agrees that it
shall not enter into any agreement, arrangement or understanding with any Person
the effect of which would be inconsistent with or violate the provisions of this
Section 4.1. NRG intends this proxy to be irrevocable and coupled with an
interest and will take such further action or execute such other instruments as
may be necessary to effectuate the intent of this proxy and hereby revokes any
proxy previously granted by it with respect to its shares of common stock of
Cogen. NRG shall not, hereafter, unless and until this Agreement terminates
pursuant to the terms hereof, purport to vote (or execute a consent with respect
to) its shares of common stock of Cogen (other than through this irrevocable
proxy) or grant any other proxy or power of attorney with respect to any such
shares, deposit such shares into a voting trust or enter into any agreement
(other than this Agreement), arrangement or understanding with any Person,
directly or indirectly, to vote, grant any proxy or give instructions with
respect to the voting of such shares.

     Section 4.2 Additional Covenants.

          (a) Cooperation. Prior to the Effective Date, each of the Stockholders
     shall use its reasonable efforts to take all actions and to do all things
     necessary, proper or advisable in order to permit the consummation of the
     Merger. The Buyer shall not cause the Merger Agreement to be amended or
     consent to any proposed amendment of the Merger Agreement, or waive any of
     its rights thereunder, in any way that would be materially adverse to NRG,
     without NRG's prior written consent.

          (b) Operation of Business. Each of the Stockholders acknowledges that
     the Company is formed solely for the purpose of effectuating the
     transactions contemplated by this Agreement and the Merger Agreement. The
     Company shall not transact any business whatsoever during the period
     commencing on the date hereof and continuing through the Effective Date
     other than in furtherance of the transactions contemplated by this
     Agreement or the Merger Agreement.

          (c) Dividend Policy. Beginning on the fourth anniversary of the
     Effective Date, the Stockholders will cause the Company to adopt
     appropriate policies of declaring dividends at the highest level permitted
     by applicable law, consistent with prudent business practices and having
     due regard for relevant business, taxation, working capital, financial
     covenant and operational requirements.

                                       12

<PAGE>   13




          (d) Securities Filings. Each of the Buyer, the Company and NRG shall
     promptly provide to any other party any information requested for the
     purpose of preparing any filings required to be filed with the Commission
     pursuant to Sections 13d and 13e of the Exchange Act, and the rules and
     regulations promulgated thereunder, in connection with this Agreement or
     the Merger Agreement and the transactions contemplated hereby and thereby.

          (e) No Solicitation. Neither NRG nor any officer, director, employee,
     representative or agent of NRG shall, directly or indirectly, solicit,
     encourage, facilitate, participate in or initiate any discussions or
     negotiations regarding, or furnish to any Person any information with
     respect to, or take any other action to facilitate any inquiries or the
     making of any submission or proposal by any Person (other than the Buyer)
     which constitutes, or may reasonably be expected to lead to, (a) any sale
     of shares of common stock of Cogen owned by NRG or (b) any Takeover
     Proposal or Superior Proposal (as such terms are defined in the Merger
     Agreement) or any agreement with respect thereto. If NRG, or any officer,
     director, employee, representative or agent of NRG, receives an inquiry or
     proposal with respect to the sale of shares of common stock of Cogen, any
     Takeover Proposal or any inquiry with respect to or which could lead to any
     sale of shares of its common stock of Cogen or any Takeover Proposal, then
     NRG shall advise the Buyer orally (within one business day) and in writing
     (as promptly as practicable) of the terms and conditions, if any, of such
     inquiry or proposal and the identity of the Person making it. NRG shall,
     and shall cause its officers, directors, employees, representatives and
     agents to, immediately cease and cause to be terminated any existing
     activities, discussions or negotiations with any parties conducted
     heretofore with respect to any of the foregoing. This Section 4.2(e) will
     bind or apply to any Person except in his or her capacity as a director of
     Cogen (or as an officer of Cogen acting at the direction of Cogen's board
     of directors) under applicable law and fiduciary duties, in which case his
     or her actions shall be restricted solely by the terms of the Merger
     Agreement.

          (f) Restrictions on Transfer, Proxies and Non Interference. Prior to
     the Effective Date, NRG hereby agrees, except as contemplated hereby, not
     to (i) acquire, sell, transfer, pledge, encumber, assign or otherwise
     dispose of, or enter into any contract, option or other arrangement or
     understanding with respect to the acquisition, sale, transfer, pledge,
     encumbrance, assignment or other disposition of, any shares of common stock
     of Cogen, (ii) grant any proxies, deposit any of its shares of

                                       13

<PAGE>   14



     common stock of Cogen into a voting trust or enter into a voting agreement
     with respect to any of its shares of common stock of Cogen, or (iii) take
     any action that would make any representation or warranty of NRG contained
     herein untrue or incorrect or have the effect of preventing or disabling
     NRG from performing its obligations under this Agreement. NRG agrees to
     notify the Buyer promptly and to provide all details requested by the Buyer
     if NRG shall be approached or solicited, directly or indirectly, by any
     Person with respect to any of the foregoing.

          (g) Stop Transfer Order. In furtherance of this Agreement,
     concurrently with the execution of this Agreement, NRG shall and hereby
     does authorize Cogen's counsel to notify Cogen's transfer agent that there
     is a stop transfer order with respect to all of NRG's shares of common
     stock of Cogen (and that this Agreement places limits on the voting and
     transfer of such shares).

          (h) Cooperation on Regulatory Matters. If so requested by the Buyer,
     promptly after the date hereof, NRG will use its reasonable best efforts to
     cause it and Cogen (if required) to make all filings which are required
     under the HSR Act and applicable requirements and to seek all regulatory
     approvals required in connection with the transactions contemplated hereby
     and by the Merger Agreement. The parties shall furnish to each other such
     necessary information and reasonable assistance as may be requested in
     connection with the preparation of filings and submissions to any
     governmental agency, including, without limitation, filings under the
     provisions of the HSR Act. NRG shall also use its reasonable efforts to
     cause Cogen to supply the Buyer with copies of all correspondence, filings
     or communications (or memoranda setting forth the substance thereof)
     between Cogen and its representatives and the Federal Trade Commission, the
     Department of Justice and any other governmental agency or authority and
     members of their respective staffs with respect to this Agreement and the
     transactions contemplated hereby.


                                    ARTICLE V

                            ADDITIONAL CONTRIBUTIONS

     Section 5.1. Additional Capital Contributions. Immediately prior to the
Effective Date, but after an affirmative vote of Cogen's stockholders approving
the Merger Agreement has been duly taken and recorded, the Buyer and NRG shall
make contributions of capital to the Company as set forth below, it being
understood that all such contributions shall be made simultaneously (the date of
such contributions being

                                       14

<PAGE>   15



referred to herein as the "Contribution Date"):

          (a) Obligations of NRG. NRG shall contribute to the Company that
     number of shares of common stock of Cogen that have, in the aggregate, a
     value (based on a $25.00 per share value) equal to (i) 20% of the Total
     Equity Value of the Company, as hereinafter defined, less (ii) the
     Adjustment Amount, as hereinafter defined, in exchange for such number of
     shares of Common Stock as would result in NRG holding 20% of the issued and
     outstanding shares of Common Stock. "Total Equity Value of the Company"
     means the sum of (i) an amount determined by multiplying (A) the total
     number of issued and outstanding shares of common stock of Cogen by (B)
     $25.00 (the "Merger Price") and (ii) the aggregate amount of the excess of
     the Merger Price over the exercise price of each of the outstanding options
     set forth on Schedule 1 hereto which are currently exercisable or will
     become exercisable upon consummation of the Transactions (as defined in the
     Merger Agreement). "Adjustment Amount" means an amount determined by
     multiplying (i) the total number of shares underlying the Cancelled
     Options, as hereinafter defined, by (ii) the excess of the Merger Price
     over the exercise price for each Cancelled Option. "Cancelled Options"
     means those options owned by David H. Peterson, Ronald J. Will and Craig A.
     Mataczynski listed on Schedule 1 to this Agreement, which, on or before the
     Merger Date, have been cancelled for no consideration and a termination
     agreement as contemplated in the Merger Agreement has been signed and
     provided to the Buyer. NRG represents that if such contribution were made
     on the date hereof and assuming that Cancelled Options includes all options
     held by David H. Peterson, Ronald J. Will and Craig A. Mataczynski, it
     would be obligated to contribute to the Company 1,394,973 shares of common
     stock of Cogen to the Company. NRG may, at its sole option, contribute to
     the Company additional shares of common stock of Cogen; provided that it
     shall own 20% of the Common Stock and shall receive no additional
     consideration in respect of any additional capital contribution of shares
     of common stock of Cogen to the Company.

          (b) Obligations of the Buyer. The Buyer shall contribute to the
     Company cash in an amount equal to 80% of the Total Equity Value of the
     Company in exchange for such number of shares of Common Stock as would
     result in the Buyer holding 80% of the issued and outstanding shares of
     Common Stock. The Buyer represents that if such contribution were made on
     the date hereof, it would be obligated to contribute $146,539,730, as
     appropriately adjusted to the extent of any contribution by NRG under the
     last sentence of Section 5.1(a) above. The requisite cash contribution by
     the Buyer shall be made in immediately available funds.

                                       15

<PAGE>   16



     Additionally, the Buyer will contribute to the Company, in the form a loan
     pursuant to a Promissory Note in the form attached hereto as Exhibit E, in
     an original principal amount not less than (i) the amount necessary to
     repay in full the debt of Cogen listed on Schedule 2 hereto, (ii) the
     amount necessary to satisfy all other obligations of the Company under this
     Agreement and the Merger Agreement or any other document related hereto or
     thereto, and (iii) transaction costs of the Company associated with the
     transactions contemplated by this Agreement and the Merger Agreement. The
     Buyer agrees that it shall not consummate the Merger without either (i)
     causing the outstanding indebtedness of Cogen's Subsidiaries to be
     refinanced on the substantially the same terms as the Promissory Note in
     the form attached hereto as Exhibit E; provided, however, that NRG shall
     have the option to participate in any such refinancing pro rata according
     to its ownership of the Company or (ii) obtaining consent of the lenders of
     Cogen's Subsidiaries to the transactions contemplated by the Merger
     Agreement or this Agreement.

     Section 5.2 NRG's Obligation to Contribute Shares. In no event shall NRG be
obligated to contribute its shares of common stock of Cogen pursuant to Section
5.1(a) unless (i) Cogen's stockholders have duly approved the Merger Agreement
and (ii) all of the conditions to closing set forth in the Merger Agreement have
been satisfied or waived.

     Section 5.3 The Buyer's Obligation to Contribute Cash. In no event shall
the Buyer be obligated to contribute cash pursuant to Section 5.1(b) above
unless all of the conditions to closing set forth in the Merger Agreement have
been satisfied or waived.


                                   ARTICLE VI

                 MANAGEMENT OF THE COMPANY FOLLOWING THE MERGER

     Section 6.1 Conduct of Business. (a) Notwithstanding the fact that no vote
may be required or that a lesser percentage vote may be specified by law, by the
Certificate of Incorporation or the By-Laws, each as amended, by any agreement
with any national securities exchange or otherwise, except as hereinafter
provided in this paragraph (a) or otherwise in this Agreement, as of the date
hereof, neither the Company nor its Subsidiaries shall take or permit any of the
following actions to be taken without the specific prior written consent of NRG
(which, at the direction of NRG, may be effectuated by the NRG Director), except
as otherwise contemplated by Article VIII or in any other provision of this
Agreement:


                                       16

<PAGE>   17



               (i)   The issuance, repurchase, exchange or redemption of any
          Shares of any Capital Stock (including any Common Stock), or the grant
          of the right or option to acquire any shares of such Capital Stock, of
          the Company.

               (ii)  Any sale or disposition of any of the Company's
          Subsidiaries and, other than in the ordinary course of business, the
          sale or disposition of property or assets of the Company or its
          Subsidiaries in excess of 20% of the fair market value of the total
          assets of the Company.

               (iii) Any amendment, modification or supplement to, or repeal
          of, or adoption of any policy or procedures inconsistent with, any
          provision of the Certificate of Incorporation or By-Laws; provided,
          that, the Company may amend the Certificate of Incorporation to effect
          a change of name or a change of registered agent for service of
          process without NRG's prior written consent.

               (iv)  Any merger, consolidation or other business combination of
          the Company with any other Person except for any merger or
          consolidation involving any direct or indirect Wholly-Owned Subsidiary
          of the Company and except for the Merger.

               (v)   The authorization or entering into by the Company or any of
          its Subsidiaries of any contract, agreement, transaction or other
          arrangement or any modification, waiver or amendment to any of the
          foregoing, with any of the Buyer or its Affiliates with a value (or
          obligation on the part of the Company or such Subsidiary) in excess of
          $2,000,000; provided that the Company or its Subsidiaries may enter
          into (x) contracts, agreements, transactions or other arrangements or
          modifications, waivers or amendments to the foregoing with any of the
          Buyer or its Affiliates with a value (or obligation on the part of the
          Company or such Subsidiary) in excess of $2,000,000 if the terms and
          provisions thereof are no less favorable to the Company or such
          Subsidiary than those that would be available in a comparable
          arms-length transaction and the Buyer shall have certified the same to
          the Board of Directors prior to the entry into or execution of the
          same, and (y) the Merger Agreement and any of the

                                       17

<PAGE>   18



          transactions or documents contemplated by the Merger Agreement.

               (vi)   The appointment or renewal of the Company's independent
          auditor if such auditor is not the Buyer's independent auditor, or any
          change in accounting periods or the accounting principles under which
          the Company's financial statements are presented except as may be
          required by GAAP or as are consistent with accounting principles used
          by the Buyer as of the date of this Agreement.

               (vii)  (a) the dissolution of the Company or any of its
          Subsidiaries, or the commencing of the process of dissolution; (b) the
          adoption of a plan of liquidation of the Company or any of its
          Subsidiaries; and (c) any action by the Company or any of its
          Subsidiaries to commence any suit, case, proceeding or other action
          (1) under the Bankruptcy Code or any other existing or future law of
          any jurisdiction relating to bankruptcy, insolvency, reorganization
          or relief of debtors seeking to have an order for relief entered with
          respect to it, or seeking to adjudicate it bankrupt or insolvent, or
          seeking reorganization, arrangement, adjustment, winding-up,
          liquidation, dissolution, composition or other relief with respect to
          it, or (2) seeking appointment of a receiver, trustee, custodian, or
          other similar official for it or for all or any substantial part of
          its assets or making a general assignment for the benefit of its
          creditors.

               (viii) The issuance of any liquidating distributions to the
          Stockholders.

          (b) The Stockholders shall take no action that would have the effect
     of causing the Company to contravene any provision of this Section 6.1.

          (c) Notwithstanding any provision in Section 6.1(a)(v), the parties
     agree that the Buyer and/or its designated Affiliates shall be permitted to
     enter into (i) Operating and Maintenance Agreements with the Company or its
     Subsidiaries in substantially the respective forms of such agreements
     existing on the date hereof between NRG and its Affiliates, on one hand,
     and Cogen's Subsidiaries, on the other hand, (ii) a Management

                                       18

<PAGE>   19



     Services Agreement, an Operating and Maintenance Agreement for the Pryor
     project and Energy Services Agreements in substantially the respective
     forms agreed to by the parties on the date hereof, and (iii) a Tax Sharing
     Agreement in substantially the form agreed to by the parties on the date
     hereof.

                                   ARTICLE VII

                           TRANSFERS OF CAPITAL STOCK

     Section 7.1 Restrictions on Transfer. Each Stockholder agrees that during
the Restricted Period, such Stockholder will not offer, sell, transfer, assign
or otherwise dispose of (or make any exchange, gift, assignment or pledge of or
impose any lien or encumbrance on) (collectively, for purposes of Sections 7 and
8 hereof only, a "Transfer") any of its shares of Common Stock, or options,
warrants or rights to subscribe for or purchase shares of Common Stock, without
the prior written consent of all the Stockholders, which consent shall not be
unreasonably withheld or delayed. For purposes of this Section 7.1, a merger or
consolidation or other business combination or any change in control of the
Buyer or the ultimate parent company of NRG will not be deemed to be a Transfer.

     Section 7.2 Exceptions to Restrictions. The provisions of Section 7.1 and
Section 8 shall not apply to any of the following transfers:

          (a) From any Stockholder to any Wholly-Owned Subsidiary of any
     Stockholder or any Person which owns 100% of the Capital Stock of any
     Stockholder (each a "Permitted Transferee"), provided that each such
     Permitted Transferee shall execute a counterpart of and become a party to
     this Agreement and shall agree in a writing in form and substance
     satisfactory to the Company to be bound and becomes bound by the terms of
     this Agreement.

          (b) Pursuant to a permitted merger or consolidation involving the
     Company or any of its Subsidiaries.

     Section 7.3 Applicability. The provisions of this Agreement shall be
applied to the shares of Common Stock acquired by any Permitted Transferee of a
Stockholder in the same manner and to the same extent as such provisions were
applicable to such Common Stock in the hands of such Stockholder.

     Section 7.4 Endorsement of Certificates.

          (a) Upon the execution of this Agreement, in addition to any

                                       19

<PAGE>   20



     other legend that the Company may deem advisable under the Securities Act
     and certain state securities laws or required pursuant to the Company's
     Certificate of Incorporation or By-Laws, all certificates representing
     issued and outstanding shares of Common Stock that are subject to any of
     the provisions of this Agreement shall be endorsed as follows:

THE SECURITIES EVIDENCED BY THIS CERTIFICATE ARE SUBJECT TO, AND ARE
TRANSFERABLE ONLY UPON COMPLIANCE WITH, THE PROVISIONS OF A STOCKHOLDERS
AGREEMENT DATED AS OF AUGUST 26, 1999, AMONG THE COMPANY AND ITS STOCKHOLDERS. A
COPY OF THE ABOVE-REFERENCED AGREEMENT IS ON FILE AT THE PRINCIPAL OFFICE OF
THE COMPANY. NO REGISTRATION OF TRANSFER OF SUCH SECURITIES WILL BE MADE ON THE
BOOKS OF THE COMPANY UNLESS AND UNTIL SUCH RESTRICTIONS SHALL HAVE BEEN COMPLIED
WITH.

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933 AND MAY NOT BE SOLD EXCEPT PURSUANT TO AN EFFECTIVE
REGISTRATION STATEMENT, OR AN EXEMPTION FROM REGISTRATION, UNDER SAID ACT.

          (b) Except as otherwise expressly provided in this Agreement, all
     certificates representing shares of Common Stock hereafter issued to or
     acquired by any of the Stockholders or their successors or assigns
     (including, without limitation, all certificates representing shares of
     Common Stock hereafter issued upon conversion of shares of Common Stock of
     any other class) shall bear the legends set forth above, and the shares of
     stock represented by such certificates shall be subject to the applicable
     provisions of this Agreement. The obligations of each party hereto shall be
     binding upon each transferee to whom shares of Common Stock are Transferred
     by any party hereto, whether or not such Transfer is permitted under the
     terms of this Agreement. Prior to consummation of any Transfer, such
     Stockholder shall cause the Transferee to execute an agreement in form and
     substance reasonably satisfactory to the other Stockholders hereto,
     providing that such Transferee shall fully comply with the terms of this
     Agreement. Prompt notice shall be given to the Company and each Stockholder
     by the transferor of any Transfer (whether or not to a Permitted
     Transferee) of any Common Stock.

     Section 7.5 Improper Transfer. Any attempt to Transfer or encumber any
shares of Common Stock other than in accordance with the terms of this Agreement
shall be null and void and neither the Company nor any transfer agent of such
securities shall give any effect to such attempted Transfer or encumbrance in
its stock records.


                                       20

<PAGE>   21



                                  ARTICLE VIII

                   RIGHTS OF FIRST REFUSAL; DRAG-ALONG RIGHTS;
                        TAG-ALONG RIGHTS; PURCHASE OPTION

     Section 8.1. Right of First Refusal.

          (a) Except for (i) Transfers to a Permitted Transferee, and (ii)
     transactions subject to Sections 8.2, 8.3, and 8.4, if at any time after
     the Restricted Period NRG receives a bona fide offer which NRG desires to
     accept (a "Transfer Offer") to sell any shares of Common Stock (or options,
     warrants or rights to subscribe for or purchase shares of Common Stock)
     owned by it, then NRG shall cause the Transfer Offer to be reduced to
     writing and shall deliver written notice of such Transfer Offer (a
     "Transfer Notice"), accompanied by a copy of such Transfer Offer to the
     Buyer and the Company, setting forth the identity of the offeror, the
     number and class of shares of Common Stock (or options, warrants or rights)
     proposed to be transferred (the "Offered Securities"), the price per
     security contained in the Transfer Offer (the "Transfer Offer Price Per
     Security"), and all other terms applicable thereto. The Transfer Notice
     shall also contain an irrevocable offer to sell the Offered Securities to
     the Buyer at a price equal to the Transfer Offer Price Per Security and
     upon substantially the same terms as contained in the Transfer Offer. In
     the event that the form of consideration specified in the Transfer Offer is
     other than cash, NRG shall use its best efforts to cause the consideration
     of such Transfer Offer to be reduced to cash. In the event that NRG is
     unsuccessful in obtaining a Transfer Offer with cash consideration, NRG
     shall not accept such Transfer Offer.

               (i)  Upon receipt of the Transfer Notice, the Buyer shall then
          have the right to accept such offer at the Transfer Offer Price Per
          Security and on the other terms specified in the Transfer Offer with
          respect to all, but not less than all, of the Offered Securities. The
          rights of the Buyer pursuant to this clause (ii) shall be exercisable
          by the delivery of notice to NRG (the "Notice of Exercise") (a copy of
          which shall also be delivered to the Company) within 30 business days
          from the date of delivery of the Transfer Notice, which Notice of
          Exercise shall be deemed an irrevocable acceptance of the Transfer
          Offer.

               (ii) In the event that the Buyer exercises its rights to purchase
          all the Offered Securities in accordance with clause (i) above, then
          NRG must sell such Offered Securities to the

                                       21

<PAGE>   22



          Buyer, at the Transfer Offer Price Per Security and on the other terms
          specified in the Transfer Offer.

          (b) If all notices required to be given pursuant to Section 8.1(a)
     have been duly given and the Buyer does not purchase the Offered Securities
     pursuant to the provisions hereof, then NRG shall have the right, subject
     to compliance by NRG with the provisions of Section 7.4(b) hereof, from the
     date which is the earlier of (i) the expiration of the option period
     pursuant to Section 8.1(a) or (ii) the date on which NRG receives notice
     from the Buyer that it will not exercise the option granted pursuant to
     Section 8.1(a), to sell to such Person which originally made the Transfer
     Offer the Offered Securities at a price per Offered Security equal to or
     greater than 100% of the Transfer Offer Price Per Security and on the other
     terms specified in the Transfer Offer.

          (c) The consummation of any purchase and sale pursuant to Section
     8.1(a) shall take place on such date, not later than 60 calendar days after
     the expiration of the option period pursuant to Section 8.1(a), as the
     purchaser shall select. Upon the consummation of any such purchase and
     sale, NRG shall deliver certificates representing the Offered Securities
     sold duly endorsed, or accompanied by written instruments of transfer in
     form satisfactory to the purchaser duly executed by NRG free and clear of
     any liens, against delivery of the Transfer Offer Price Per Security for
     each of the Offered Securities purchased by federal funds wired to such
     bank or financial institution specified in writing by NRG. If the purchase
     and sale is not consummated within the 60 calendar day period referred to
     in this subsection (c), then the provisions of Section 8.1 shall again
     apply to such shares.

     Section  8.2.  Drag-Along.

          (a) Subject to any approval or other rights in this Agreement, if
     after the expiration of the Restricted Period, the Buyer sells all or
     substantially all the Fully Diluted Common Stock owned by it (whether
     pursuant to a sale, merger or other consolidation, a "Company Sale") in a
     bona fide arm's-length transaction to a third party that is not an
     Affiliate of the Buyer or of the Company (an "Independent Third Party"),
     then the Buyer shall have the right, subject to all the provisions of this
     Section 8.2 ("Drag-Along Right"), to require NRG to (i) if such Company
     Sale is structured as a sale of stock, sell, transfer and deliver or cause
     to be sold, transferred and delivered to such Independent Third Party all
     shares of Fully Diluted Common Stock, owned or held by it or (ii) if such
     Company Sale requires the consent or approval of the Company's
     stockholders, vote

                                       22

<PAGE>   23



     NRG's shares of Common Stock in favor thereof, and, in any such event,
     except to the extent otherwise provided in subsection (c) of this Section
     8.2, NRG shall agree to and shall be bound by the same terms, provisions
     and conditions in respect of the Company Sale as are applicable to the
     Buyer. The provisions of Section 8.1 shall not apply to any transactions to
     which this Section 8.2 applies.

          (b) If the Buyer desires to exercise its Drag-Along Rights, it shall
     give written notice to the other Stockholder ("Drag-Along Notice") of the
     Company Sale, setting forth the name and address of the transferee, the
     date on which such transaction is proposed to be consummated (which shall
     be not less than 30 days after the date such Drag-Along Notice is given),
     and the proposed amount of cash consideration and terms and conditions of
     payment offered by such transferee.

          (c) The obligations of the Stockholders in respect of a Company Sale
     under this Section 8.2 are subject to the satisfaction of the following
     conditions: (i) subject to (v) below, upon the consummation of the Company
     Sale, consideration of equivalent value in cash or Cash Equivalents
     realized upon such Company Sale shall be paid or distributed in respect of
     each share of Common Stock then issued and outstanding; (ii) each holder of
     then currently exercisable rights to acquire shares of Common Stock will be
     given a reasonable opportunity to exercise such rights prior to the
     consummation of the Company Sale and thereby to participate in such sale as
     a holder of such Common Stock; (iii) there shall be no liability of NRG for
     indemnification in respect of any matters arising pursuant to or in
     connection with the Company Sale, other than with respect to NRG's
     ownership of its shares of Common Stock; (iv) NRG shall not be required to
     make general representations or warranties regarding the financial
     condition, business, assets or affairs of the Company and its Subsidiaries;
     (v) the valuation of NRG's shares of Common Stock shall take into account
     not only the consideration received by the Buyer for its Common Stock but
     also any consideration received by the Buyer or its for the sale, transfer
     or disposition of any ownership or other interests, contract rights,
     permits or any other asset of the Buyer or its Affiliates with respect to
     its investment in the Company related to or contemplated by the sale of the
     Buyer's Common Stock; and (vi) NRG shall be given a reasonable opportunity
     to review and provide comments to the agreements or documents relating to
     the Company Sale.


                                       23

<PAGE>   24




     Section 8.3 Tag-Along Rights.

          (a) Notwithstanding anything in this Agreement to the contrary,
     except in the case of (i) transfers to a Permitted Transferee referred to
     in Section 7.2 and (ii) transactions subject to Section 8.2, the Buyer
     shall not sell, dispose of or otherwise transfer any shares of Common
     Stock, options, warrants or rights to subscribe for or purchase shares of
     Common Stock, unless, prior to the consummation thereof, NRG shall have
     been afforded the opportunity to join in such sale with respect to all of
     the shares of Common Stock owned by NRG, as hereinafter provided in this
     Section 8.3.

          (b) Prior to consummation of any proposed sale, disposition or
     transfer of shares of Common Stock (or options, warrants or rights)
     described in Section 8.3(a), the Buyer (the "Disposing Stockholder") shall
     cause the person or group that proposes to acquire such shares (the
     "Proposed Purchaser") to offer NRG in writing ("Purchase Offer") the right
     to sell all of the shares of Common Stock (or options, warrants or rights)
     owned by NRG. The Purchase Offer shall be accompanied by a copy of the
     Proposed Purchaser's final offer to the Disposing Stockholder. If the
     Purchase Offer is accepted by NRG, then the number of shares of Common
     Stock (or options, warrants or rights) to be sold to the Proposed Purchaser
     by the Disposing Stockholder shall be reduced by the aggregate number of
     shares of Common Stock (or options, warrants or rights) to be purchased by
     the Proposed Purchaser from NRG pursuant thereto. Such purchase shall be
     made on the same terms and conditions as the Proposed Purchaser shall have
     offered to purchase shares of Common Stock to be sold by the Disposing
     Stockholder (net, in the case of any options, warrants or rights, of any
     amounts required to be paid by the holder upon exercise thereof); provided,
     however, that the valuation of NRG's Common Stock shall take into account
     not only the consideration received by the Buyer for its Common Stock but
     also only consideration received by the Buyer or its Affiliates for the
     sale, transfer or disposition of any ownership or other interests, contract
     rights, permits or any other asset of the Buyer or its Affiliates with
     respect to its investment in the Company related to or contemplated by the
     sale of the Buyer's Common Stock. NRG shall have 30 days from the date of
     receipt of the Purchase Offer during which to accept such Purchase Offer,
     and the closing of such purchase shall occur within 30 days after such
     acceptance or at such other time as NRG and the Proposed Purchaser may
     agree.



                                       24

<PAGE>   25




     Section 8.4 Purchase Option.

          (a) The Buyer shall, for a period of 365 days commencing on the day
     after the expiration of the Restricted Period (the "Option Period"), have
     the option to acquire from NRG all, but not less than all, of the shares of
     Common Stock held by NRG (the "Option").

          (b) In the event that the Buyer determines that it may exercise the
     Option, it shall, at any time during the Option Period or within the 60
     days prior to the commencement of the Option Period, give notice to NRG
     that it intends to obtain a fair market value determination pursuant to
     this Section 8.4 (the "Valuation Notice"). The fair market value of the
     Company shall be determined by one nationally recognized and independent
     investment bank mutually acceptable to NRG and the Buyer (the "Valuing
     Investment Bank"), it being understood that for the purpose of this Section
     8.4 an independent investment bank shall be one which is neither affiliated
     with nor employed as the primary investment banking firm of NRG, the Buyer
     or the Company. The Buyer shall include in its Valuation Notice a list of
     at least three (3) investment banks acceptable to the Buyer as the Valuing
     Investment Bank and satisfying the criteria set forth in the preceding
     sentence. Upon receipt of such list, NRG shall promptly notify the Buyer
     which of such investment banks, if any, is acceptable to it. If NRG rejects
     each such investment bank as unacceptable to it, NRG shall promptly notify
     the Buyer of the identity of at least three investment banks acceptable to
     NRG and satisfying the criteria set forth in the second sentence of this
     paragraph. Upon receipt of such notice, the Buyer shall promptly notify NRG
     which of such investment banks, if any, is acceptable to it. NRG and the
     Buyer shall each act with such promptness and diligence that the procedures
     described in the foregoing sentences will result in the selection of a
     Valuing Investment Bank in as short a period of time as practicable. NRG
     and the Buyer shall each be responsible for 50% of the total fees and
     expenses charged by the Valuing Investment Bank; provided, however, in the
     event that the Buyer does not exercise the Option, the Buyer shall be
     responsible for 100% percent of the total fees and expenses charged by the
     Valuing Investment Bank.

          (c) The Valuing Investment Bank may use, among other methodologies,
     discounted cash flow, comparable transaction and traded company analyses to
     determine the fair market value of the Company. In determining the fair
     market value of the Company, the Valuing Investment Bank shall evaluate the
     Company (i) without any consideration of the


                                       25

<PAGE>   26



     management fee to be paid to the Buyer under Section 9.3, (ii) without
     factoring in any discount arising from NRG's minority ownership position
     and limited representation on the Company's Board of Directors, and (iii)
     without any consideration of any discount applicable to an initial Public
     Offering. Moreover, to the extent that, as of the time of the valuation
     determination, financing for the Company or its Subsidiaries or their
     generation assets is available under terms more favorable than those terms
     in place, the more favorable financing terms shall be utilized by the
     Valuing Investment Bank in its fair market value determination; provided,
     however, that to the extent the financing for any of the Subsidiaries at
     the time of such valuation is on substantially the same material economic
     terms as the financing for such Subsidiary on the date hereof, such
     financing terms shall be utilized by the Valuing Investment Bank in its
     fair market value determination.

          (d) In the event that the Buyer wishes to exercise the Option, the
     aggregate price payable to NRG for its Common Stock (the "Option Price")
     shall be equal to NRG's Pro Rata Portion of the fair market value of the
     Company (on a consolidated basis) as determined by the Valuing Investment
     Bank pursuant to Section 8.4(c) above. The Buyer shall exercise the Option
     by providing written notice to NRG prior to the expiration of the Option
     Period, which notice shall be irrevocable.

     Section 8.5 Waiver. For purposes of this Article VIII, any Person who has
failed to give notice of the election of an option hereunder within the
specified time period will be deemed to have waived its rights with respect
thereto on the day immediately following the last day of such period.


                                   ARTICLE IX

                               CERTAIN AGREEMENTS

     Section 9.1. Access to Information Regarding Subsidiaries. The Buyer and
the Company shall cause the NRG Director to be provided with all material
information regarding the Company's Subsidiaries, including without limitation
their respective business, operations, property, assets, condition (financial or
otherwise) or prospects thereof, and such other information regarding the
Company's Subsidiaries as the NRG Director, may reasonably request. NRG shall at
all times preserve in strict confidence all information of a proprietary or
confidential nature relating to the business of the Company and which is
acquired by virtue of this Agreement and shall use all such information solely
in connection with the monitoring of NRG's investment in the Company; provided,
that NRG shall be entitled to disclose any such information in


                                       26

<PAGE>   27



confidence to any of its professional advisors or publicly disclose such
information to the extent required by law, regulation or Commission filing.

     Section 9.2. Financial Statements; Inspections.

          (a) The Company and the Buyer shall provide NRG with (i) the unaudited
     consolidated and consolidating quarterly financial statements of the
     Company and each of its Subsidiaries for each calendar quarter within 35
     days of the end of such calendar quarter, and (ii) the audited consolidated
     and consolidating financial statements of the Company and each of its
     Subsidiaries for each calendar year within 70 days after the end of each
     calendar year.

          (b) NRG's independent auditors shall, for purposes of certifying the
     financial statements of NRG and its direct and indirect parents, have the
     right, upon reasonable prior notice to the Company, to visit and inspect
     the properties of the Company and its Subsidiaries and to examine and copy
     (at NRG's own expense) their books of record and accounts, and to discuss
     their affairs, finances, and accounts with their officers and their current
     and prior independent public accountants, all at such times (during normal
     business hours) as NRG may reasonably request. The foregoing rights are in
     addition, and are not intended to limit, any rights that NRG may have under
     the law of the State of Delaware, including Sections 219 and 220 of the
     Delaware General Corporation Law.

     Section 9.3 Management Fee.

          (a) The Company shall pay to the Buyer a management fee (the
     "Management Fee") determined in accordance with the provisions of this
     Section 9.3(a). The Management Fee shall be determined in arrears following
     each calendar year and shall be equal to the amount, if any, by which
     Actual Adjusted Net Income for the immediately preceding calendar year
     exceeds the Projected Adjusted Net Income for such calendar year. No
     Management Fee shall be payable with respect to the year ending December
     31, 1999.

          "Actual Adjusted Net Income" shall mean, for any period, the
     consolidated net income of the Company for such period determined in
     accordance with GAAP consistently applied, except that such amount shall be
     (i) increased by the taxes that were deducted from operating income to
     arrive at net income for such period, (ii) adjusted to exclude any accrual
     made for estimated management fees for such period, and (iii) calculated
     without regard to any extraordinary items of income or expense

                                       27

<PAGE>   28



     in such period or other transactions not in the ordinary course of the
     Company's business in such period.

          "Projected Adjusted Net Income" shall mean, for any period, the
     projected pre-tax net income for such period set forth on Schedule 3
     hereto, as amended with respect to the line items indicated on Schedule 3,
     to take account of the adjusted book basis amount and depreciation amount
     for the applicable period set forth on a schedule approved by the parties
     as soon as reasonably practicable following the Effective Date. Projected
     Adjusted Net Income with respect to the year ending December 31, 2000 shall
     be pro-rated to the extent the Effective Date occurs after December 31,
     1999 (such pro-ration to be calculated on the basis of the number of days
     after the Effective Date remaining in the year divided by 365).

          (b) Notwithstanding the foregoing, the obligations of the Company to
     pay the Management Fee shall be null and void and shall no longer apply to
     any calendar year after the fourth anniversary of the Effective Date.

                                    ARTICLE X

                               REGISTRATION RIGHTS

     Section 10.1 Piggyback Registrations.

          (a) In no event shall the Company register any of its equity
     securities during the Restricted Period. If, at any time after the fourth
     anniversary of the Effective Date, the Company at any time proposes to
     register any of its equity securities under the Securities Act, whether or
     not for sale for its own account, on a form and in a manner that would
     permit registration of Registrable Securities for sale to the public under
     the Securities Act, it will give written notice to all the holders of
     Registrable Securities promptly of its intention to do so, describing such
     securities and specifying the form and manner and the other relevant facts
     involved in such proposed registration, including, without limitation, (x)
     the intended method of disposition of the securities offered, including
     whether or not such registration will be effected through an underwriter in
     an underwritten offering or on a "best efforts" basis, and, in any case,
     the identity of the managing underwriter, if any, and (y) the price at
     which the Registrable Securities are reasonably expected to be sold. Upon
     the written request of any holder of Registrable Securities delivered to
     the Company within 30 calendar days after the receipt of any such notice

                                       28

<PAGE>   29



     (which request shall specify the Registrable Securities intended to be
     disposed of by such holder), the Company will effect the registration under
     the Securities Act of all the Registrable Securities that the Company has
     been so requested to register; provided, however, that:

                    (i)  if, at any time after giving such written notice of its
              intention to register any securities and prior to the effective
              date of the registration statement filed in connection with such
              registration, the Company shall reasonably determine not to
              register such securities, the Company may, at its election, give
              written notice of such determination to each holder of Registrable
              Securities who shall have made a request for registration as
              hereinabove provided and thereupon the Company shall be relieved
              of its obligation to register any Registrable Securities in
              connection with such registration (but not from its obligation to
              pay the Registration Expenses in connection therewith), without
              prejudice, however, to the right of any Person to request that
              such registration be effected as a registration under this Section
              10.1; and

                    (ii) if such registration involves an Underwritten Offering,
              all holders of Registrable Securities requesting to be included in
              the Company's registration must sell their Registrable Securities
              to the underwriters selected by the Company on the same terms and
              conditions as apply to the Company.

          (b) The Company shall not be obligated to effect any registration of
     Registrable Securities under this Section 10.1 incidental to the
     registration of any of its securities in connection with mergers,
     acquisitions, exchange offers, dividend reinvestment plans or stock option
     or other employee benefit plans.

          (c) If a registration pursuant to this Section 10.1 involves an
     underwritten offering and the managing underwriter advises the issuer that,
     in its opinion, the number of securities proposed to be included in such
     registration should be limited due to market conditions, the Company will
     so advise each holder of Registrable Securities that has requested
     registration pursuant to Section 10.1(a), and shares shall be excluded from
     such offering in the following order until such limitation has been met:
     First, the Registrable Securities requested to be included in such offering
     by a Stockholder other than a NRG or any Permitted Transferee of NRG


                                       29

<PAGE>   30



     shall be excluded pro rata, based on the respective number of Registrable
     Securities as to which registration has been so requested by such
     Stockholders, until all such Registrable Securities shall have been so
     excluded; second, the Registrable Securities requested to be included in
     such offering by NRG or any Permitted Transferee of NRG shall be excluded
     pro rata, based on the respective number of Registrable Securities as to
     which registration has been so requested by NRG or any Permitted Transferee
     of NRG, until all such Registrable Securities shall have been so excluded;
     and thereafter, the securities requested to be registered by the Company
     shall be excluded.

          (d) In connection with any underwritten offering with respect to which
     holders of Registrable Securities shall have requested registration
     pursuant to this Section 10.1, the Company shall have the right to select
     the managing underwriter with respect to the offering; provided that such
     managing underwriter shall be a nationally recognized investment banking
     firm.

          (e) The Company will pay all Registration Expenses incurred in
     connection with each of the registrations of Registrable Securities
     effected by it pursuant to this Section 10.1.


                                   ARTICLE XI

                                   TERMINATION

     Section 11.1. Termination.

          (a) The provisions of this Agreement shall terminate on the date on
     which any of the following events first occurs: (i) an initial Public
     Offering or, (ii) the Merger Agreement is terminated in accordance with its
     terms.

          (b) Notwithstanding the foregoing, this Agreement shall in any event
     terminate with respect to any Stockholder when such Stockholder no longer
     owns any shares of Common Stock, or other warrants, options or rights to
     subscribe for or purchase Common Stock.




                                       30

<PAGE>   31




                                   ARTICLE XII

                                  MISCELLANEOUS

     Section 12.1. Successors and Assigns. Except as otherwise provided herein,
all the terms and provisions of this Agreement shall be binding upon, shall
inure to the benefit of and shall be enforceable by the respective successors
and assigns of the parties hereto. No Stockholder may assign any of its rights
or obligations hereunder to any Person other than in accordance with this
Agreement to a transferee that has complied in all respects with the
requirements of this Agreement. The Company may not assign any of its rights or
obligations hereunder to any other Person. If any transferee of any Stockholder
shall acquire any shares of Common Stock in any manner, whether by operation of
law or otherwise, such shares shall be held subject to all of the terms of this
Agreement, and by taking and holding such shares such Person shall be entitled
to receive the benefits of and be conclusively deemed to have agreed to be bound
by and to comply with all of the terms and provisions of this Agreement.

     Section 12.2. Amendment and Modification; Waiver of Compliances; Conflicts.

          (a) This Agreement may be amended only by a written instrument duly
     executed by each of the Stockholders party hereto. In the event of the
     amendment or modification of this Agreement in accordance with its terms,
     the Stockholders shall cause the Board of Directors to meet within 30
     calendar days following such amendment or modification or as soon
     thereafter as is practicable for the purpose of adopting any amendment to
     the Certificate of Incorporation and By-Laws that may be required as a
     result of such amendment or modification to this Agreement, and, if
     required, proposing such amendments to the Stockholders entitled to vote
     thereon, and the Stockholders agree to vote in favor of such amendments.

          (b) Except as otherwise provided in this Agreement, any failure of any
     of the parties to comply with any obligation, covenant, agreement or
     condition herein may be waived by the party entitled to the benefits
     thereof only by a written instrument signed by the party granting such
     waiver, but such waiver or failure to insist upon strict compliance with
     such obligation, covenant, agreement or condition shall not operate as a
     waiver of, or estoppel with respect to, any subsequent or other failure.

          (c) In the event of any conflict between the provisions of this
     Agreement and the provisions of any other agreement, the provisions of

                                       31

<PAGE>   32

     this Agreement shall govern and prevail.

     Section 12.3. Notices. All notices and other communications provided for
hereunder shall be in writing and delivered by hand or sent by first class mail
or sent by telecopy (with such telecopy to be confirmed promptly in writing sent
by first class mail), sent as follows:

                  (i)      If to the Buyer, addressed to

                           Calpine Corporation
                           50 West San Fernando Street
                           San Jose, California  95113
                           Attention:  John T. King
                           Telecopy:  (408) 995-0505

                           with a copy to:

                           Howard, Smith & Levin LLP
                           1330 Avenue of the Americas
                           New York, New York 10019
                           Attention:  William R. Collins, Esq.
                           Telecopy No.:  (212) 841-1010

                  (ii)     If to NRG, addressed to

                           NRG Energy, Inc.
                           1221 Nicollet Mall, Sutie 700
                           Minneapolis, Minneapolis 55403-2445
                           Attention:  James J. Bender, Esq.
                           Telecopy No.:  (612) 373-5392

                           with a copy to

                           Skadden, Arps, Slate, Meagher & Flom LLP
                           1440 New York Avenue NW
                           Washington, D.C. 20005
                           Attention:  Jeanine L. Matte, Esq.
                           Telecopy No.: (202) 393-5760



                                       32

<PAGE>   33




                  (iii)    If to the Company, addressed to

                           Cogeneration Corporation of America
                           c/o Calpine Corporation
                           50 West San Fernando Street
                           San Jose, California  95113
                           Attention:  John T. King
                           Telecopy No.:  (408) 995-0505

                           with a copy to

                           Howard, Smith & Levin LLP
                           1330 Avenue of the Americas
                           New York, New York 10019
                           Attention:  William R. Collins, Esq.
                           Telecopy No.:  (212) 841-1010

or to such other address or addresses or telecopy number or numbers as any of
the parties hereto may most recently have designated in writing to the other
parties hereto by such notice. All such communications shall be deemed to have
been given or made when so delivered by hand or sent by telecopy, or three
business days after being so mailed.

     Section 12.4 Entire Agreement: Governing Law; Consent to Jurisdiction

          (a) This Agreement and the other writings referred to herein or
     delivered pursuant hereto which form a part hereof contain the entire
     agreement among the parties hereto with respect to the subject transactions
     contemplated hereby and supersede all prior oral and written agreements and
     memoranda and undertakings among the parties hereto with regard to this
     subject matter. The Company represents to the Stockholders that the rights
     granted to the holders hereunder do not in any way conflict with and are
     not inconsistent with the rights granted or obligations accepted under any
     other agreement (including the Certificate of Incorporation) to which the
     Company is a party. Neither the Company nor any Subsidiary of the Company
     will hereafter enter into any agreement with respect to its equity or debt
     securities which is inconsistent with the rights granted to any Stockholder
     under this Agreement without obtaining the prior written consent of the
     Stockholder whose rights would be thereby affected.

          (b) This Agreement shall be governed by and construed in accordance
     with the laws of the State of Delaware (without giving effect to the choice
     of law principles thereof).

                                       33

<PAGE>   34

          (c) Each of the parties hereto (a) consents to submit itself to the
     personal jurisdiction of any federal court located in the State of Delaware
     or any Delaware state court in the event any dispute arises out of this
     Agreement or any of the transactions contemplated by this Agreement, (b)
     agrees that it will not attempt to deny or defeat such personal
     jurisdiction by motion or other request for leave from any such court and
     (c) agrees that it will not bring any action relating to this Agreement or
     any of the transactions contemplated by this Agreement in any court other
     than a federal or state court sitting in the State of Delaware.

     Section 12.5. Severability. The validity or unenforceability of any
provisions of this Agreement in any jurisdiction shall not affect the validity,
legality or enforceability of the remainder of this Agreement in such
jurisdiction or the validity, legality or enforceability of this Agreement,
including any such provision, in any other jurisdiction, it being intended that
all rights and obligations of the parties hereunder shall be enforceable to the
fullest extent permitted by law.

     Section 12.6. Injunctive Relief. The Stockholders acknowledge and agree
that a violation of any of the terms of this Agreement will cause the
Stockholders irreparable injury for which an adequate remedy at law is not
available. Therefore, the Stockholders agree that each Stockholder shall be
entitled, in addition to any other remedy to which they may be entitled at law
or in equity, (i) to an injunction, restraining order or other equitable relief
from any court of competent jurisdiction, restraining any Stockholder from
committing any violations of the provisions of this Agreement, and (ii) to
compel specific performance of the terms of this Agreement.

     Section 12.7. Availability of Agreement. For so long as this Agreement
shall be in effect, this Agreement shall be made available for inspection by any
Stockholder upon request at the principal executive offices of the Company.

     Section 12.8. Headings. The section and paragraph headings contained in
this Agreement are for reference purposes only and shall not affect in any way
the meaning or interpretation of this Agreement.

     Section 12.9. Expenses. Except as otherwise expressly provided in Section
5.1(b) or any other provision of this Agreement, each of the Buyer, the Company
and NRG will bear its own costs and expenses incurred in connection with this
Agreement and the transactions contemplated hereby and the Merger. This Section
12.9 shall survive the termination of this Agreement.

     Section 12.10. Adjustments to Prevent Dilution, Etc. In the event of a
stock dividend or distribution, or any change in the common stock of Cogen by
reason of

                                       34

<PAGE>   35



any stock dividend, split-up, reclassification, recapitalization, combination or
the exchange of shares, the term "shares" used herein shall be deemed to refer
to and include the shares of common stock of Cogen owned by NRG as well as such
stock dividends and distributions and any shares into which or for which any or
all of the shares of common stock of Cogen may be changed or exchanged. In such
event, the amount to be paid per share by the Buyer shall be proportionately
reduced.

     Section 12.11. Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

                      [The next page is the signature page]


                                       35

<PAGE>   36


     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the date first above written.


                               CALPINE CORPORATION


                               By: /s/ John T. King
                                  ------------------------------------------
                               Name:  John T. King
                               Title: Vice President - Business Development


                                NRG ENERGY, INC.


                               By: /s/ David H. Peterson
                                  ------------------------------------------
                               Name:  David H. Peterson
                               Title: Chairman, President and
                                      Chief Executive Officer


                               CALPINE EAST ACQUISITION CORP.


                               By: /s/ John T. King
                                  ------------------------------------------
                               Name:  John T. King
                               Title: Vice President




                                       36

<PAGE>   1
                                                                     EXHIBIT (d)


                      COGENERATION CORPORATION OF AMERICA

                         One Carlson Parkway, Suite 240
                       Minneapolis, Minnesota 55447-4454

                               November   , 1999

Dear Stockholder:

     You are cordially invited to attend a special meeting of stockholders of
Cogeneration Corporation of America ("CogenAmerica") to be held on December   ,
1999 at 9:00 a.m., local time, at [INSERT LOCATION OF SPECIAL MEETING].
Stockholders of record as of November   , 1999 are entitled to vote at the
special meeting.

     At the special meeting, you will be asked to approve (1) the merger of a
subsidiary of Calpine Corporation with and into CogenAmerica and (2) an
amendment to CogenAmerica's certificate of incorporation to facilitate the
merger. As a result of the merger, you will receive $25.00 in cash for each
share of CogenAmerica common stock which you own and CogenAmerica will be owned
80% by Calpine and 20% by NRG Energy, Inc., an existing stockholder.

     THE COGENAMERICA BOARD OF DIRECTORS, BASED UPON THE UNANIMOUS
RECOMMENDATION OF THE INDEPENDENT DIRECTORS COMMITTEE, COMPRISED OF THREE
DISINTERESTED DIRECTORS, HAS DETERMINED THAT THE MERGER AGREEMENT IS ADVISABLE
AND IS FAIR TO, AND IN THE BEST INTERESTS OF, THE STOCKHOLDERS OF COGENAMERICA
(OTHER THAN NRG ENERGY, INC.), AND HAS UNANIMOUSLY APPROVED THE MERGER AGREEMENT
AND THE AMENDMENT AND HAS UNANIMOUSLY RECOMMENDED THAT THE COGENAMERICA
STOCKHOLDERS APPROVE AND ADOPT THE MERGER AGREEMENT AND THE AMENDMENT.

     Approval and adoption of the merger agreement at the special meeting
requires the affirmative vote of the holders of more than 66 2/3% of the
outstanding shares of CogenAmerica common stock entitled to vote at the special
meeting. Approval of the charter amendment at the special meeting requires the
affirmative vote of the holders of more than 50% of the outstanding shares of
CogenAmerica common stock entitled to vote at the special meeting.

     EVEN IF YOU PLAN TO ATTEND THE MEETING, WE URGE YOU TO MARK, SIGN AND DATE
THE ENCLOSED PROXY AND RETURN IT PROMPTLY. You have the option to revoke it at
any time or to vote your shares personally on request if you attend the special
meeting of stockholders. If the merger agreement and the charter amendment are
approved by the stockholders, you will receive instructions as soon as
practicable after completion of the merger on how to surrender your shares to
receive payment.
                                          Sincerely,

                                          David H. Peterson, Chairman
<PAGE>   2

                      COGENERATION CORPORATION OF AMERICA

                         One Carlson Parkway, Suite 240
                       Minneapolis, Minnesota 55447-4454

                               November   , 1999

Dear Stockholder:

     You are cordially invited to attend a special meeting of stockholders of
Cogeneration Corporation of America ("CogenAmerica") to be held on December   ,
1999 at 9:00 a.m., local time, at [INSERT LOCATION OF SPECIAL MEETING].
Stockholders of record as of November   , 1999 are entitled to vote at the
special meeting.

     At the special meeting, you will be asked to approve (1) the merger of a
subsidiary of Calpine Corporation with and into CogenAmerica and (2) an
amendment to CogenAmerica's certificate of incorporation to facilitate the
merger. As a result of the merger, you will receive $25.00 in cash for each
share of CogenAmerica common stock which you own and CogenAmerica will be owned
80% by Calpine and 20% by NRG Energy, Inc., an existing stockholder.

     THE COGENAMERICA BOARD OF DIRECTORS, BASED UPON THE UNANIMOUS
RECOMMENDATION OF THE INDEPENDENT DIRECTORS COMMITTEE, COMPRISED OF THREE
DISINTERESTED DIRECTORS, HAS DETERMINED THAT THE MERGER AGREEMENT IS ADVISABLE
AND IS FAIR TO, AND IN THE BEST INTERESTS OF, THE STOCKHOLDERS OF COGENAMERICA
(OTHER THAN NRG ENERGY, INC.), AND HAS UNANIMOUSLY APPROVED THE MERGER AGREEMENT
AND THE AMENDMENT AND HAS UNANIMOUSLY RECOMMENDED THAT THE COGENAMERICA
STOCKHOLDERS APPROVE AND ADOPT THE MERGER AGREEMENT AND THE AMENDMENT.

     Approval and adoption of the merger agreement at the special meeting
requires the affirmative vote of the holders of more than 66 2/3% of the
outstanding shares of CogenAmerica common stock entitled to vote at the special
meeting. Approval of the charter amendment at the special meeting requires the
affirmative vote of the holders of more than 50% of the outstanding shares of
CogenAmerica common stock entitled to vote at the special meeting.

     EVEN IF YOU PLAN TO ATTEND THE MEETING, WE URGE YOU TO MARK, SIGN AND DATE
THE ENCLOSED PROXY AND RETURN IT PROMPTLY. You have the option to revoke it at
any time or to vote your shares personally on request if you attend the special
meeting of stockholders. If the merger agreement and the charter amendment are
approved by the stockholders, you will receive instructions as soon as
practicable after completion of the merger on how to surrender your shares to
receive payment.
                                          Sincerely,

                                          David H. Peterson, Chairman
<PAGE>   3

                      COGENERATION CORPORATION OF AMERICA

                         One Carlson Parkway, Suite 240
                       Minneapolis, Minnesota 55447-4454

                   NOTICE OF SPECIAL MEETING OF STOCKHOLDERS
                        TO BE HELD ON DECEMBER    , 1999

To the Stockholders of Cogeneration Corporation of America:

     Notice is hereby given that a special meeting of stockholders of
Cogeneration Corporation of America ("CogenAmerica"), will be held on December
  , 1999 at 9:00 a.m., local time, at [INSERT LOCATION OF SPECIAL MEETING]:

          (1) To consider and vote upon a proposal to approve and adopt the
     Agreement and Plan of Merger, dated as of August 26, 1999, pursuant to
     which Calpine East Acquisition Corp., a Delaware corporation ("Acquisition
     Sub") and a subsidiary of Calpine Corporation, a Delaware corporation, will
     be merged with and into CogenAmerica, and each outstanding share of
     CogenAmerica common stock, $.01 par value, other than shares owned by
     CogenAmerica, Acquisition Sub and stockholders who exercise their appraisal
     rights, will be converted into the right to receive $25.00 in cash. A copy
     of the merger agreement is attached as Appendix A to the accompanying proxy
     statement. The merger agreement is also summarized in the proxy statement.

          (2) To consider and vote upon a proposal to amend CogenAmerica's
     certificate of incorporation to permit NRG Energy, Inc., a Delaware
     corporation ("NRG"), to transfer and contribute shares of CogenAmerica
     common stock owned by NRG to Acquisition Sub immediately prior to
     consummation of the merger so that, upon completion of the merger, NRG will
     retain a 20% equity interest in CogenAmerica. A copy of the proposed
     amendment is attached as Appendix B to the accompanying proxy statement.
     The amendment is also summarized in the proxy statement.

          (3) To consider and act upon such other matters as may properly come
     before the special meeting or any adjournment or adjournments thereof.

     A proxy card and a proxy statement containing more detailed information
with respect to the matters to be considered at the special meeting accompany
this notice.

     THE INDEPENDENT DIRECTORS COMMITTEE AND THE BOARD OF DIRECTORS OF
COGENAMERICA HAVE UNANIMOUSLY APPROVED THE MERGER AGREEMENT AND THE CHARTER
AMENDMENT AND RECOMMEND THAT THE STOCKHOLDERS APPROVE AND ADOPT THE MERGER
AGREEMENT AND THE CHARTER AMENDMENT.

     Only holders of CogenAmerica common stock of record at the close of
business on November   , 1999, are entitled to notice of, and to vote at, the
special meeting. The quorum required to hold the special meeting is 60% of the
shares of CogenAmerica common stock entitled to vote at the meeting, present in
person or by proxy. The affirmative vote of more than 66 2/3% of the outstanding
shares of CogenAmerica common stock is required to approve the merger agreement
and the affirmative vote of more than 50% of the outstanding shares of
CogenAmerica common stock is required to approve the

                                        3
<PAGE>   4

amendment to CogenAmerica's certificate of incorporation. Each stockholder who
signs and returns a proxy in the form enclosed with this proxy statement may
revoke the same at any time prior to its use by giving notice of such revocation
to CogenAmerica in writing or in person at the special meeting. Unless so
revoked, the shares represented by each proxy will be voted at the special
meeting and at any adjournments thereof. Presence at the special meeting of a
stockholder who has signed a proxy does not alone revoke that proxy.

     Holders of CogenAmerica common stock who do not vote their shares in favor
of the merger agreement and who strictly comply with Section 262 the Delaware
General Corporation Law (the "DGCL") have appraisal rights to make written
demand for payment of the "fair value" of their shares. For a description of the
appraisal rights of stockholders, see Section 262 of the DGCL, a copy of which
is attached as Appendix D to the accompanying proxy statement. In addition, a
description of procedures to be followed in order to exercise appraisal rights
is set forth in the accompanying proxy statement.

     It is very important that your shares be represented at the special
meeting. You are urged to complete and sign the accompanying proxy card, which
is solicited by the CogenAmerica Board of Directors, and mail it promptly in the
enclosed envelope.

                                          BY ORDER OF THE BOARD OF DIRECTORS

                                          Thomas L. Osteraas
                                          Secretary

Minneapolis, Minnesota
November   , 1999

     PLEASE DO NOT SEND YOUR STOCK CERTIFICATES AT THIS TIME. IF THE MERGER IS
COMPLETED, YOU WILL BE SENT INSTRUCTIONS REGARDING THE SURRENDER OF YOUR STOCK
CERTIFICATES.

     WHETHER OR NOT YOU ARE ABLE TO ATTEND THE MEETING, PLEASE SIGN, DATE AND
RETURN THE ACCOMPANYING PROXY CARD PROMPTLY IN THE ENCLOSED ENVELOPE WHICH
REQUIRES NO POSTAGE IF MAILED IN THE UNITED STATES.

     THE TRANSACTION HAS NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION NOR HAS THE COMMISSION PASSED UPON THE FAIRNESS OR MERITS OF
THE TRANSACTION NOR UPON THE ACCURACY OR ADEQUACY OF THE INFORMATION CONTAINED
IN THIS DOCUMENT, INCLUDING THE ACCOMPANYING PROXY STATEMENT. ANY REPRESENTATION
TO THE CONTRARY IS UNLAWFUL.

                                        4
<PAGE>   5

                      COGENERATION CORPORATION OF AMERICA

                         One Carlson Parkway, Suite 240
                       Minneapolis, Minnesota 55447-4454

                                PROXY STATEMENT
                      FOR SPECIAL MEETING OF STOCKHOLDERS
                        TO BE HELD ON DECEMBER    , 1999

                     QUESTIONS AND ANSWERS ABOUT THE MERGER

Q: What will happen in the merger?

A: In the merger, a subsidiary of Calpine Corporation will be merged into
CogenAmerica, and CogenAmerica will be the surviving corporation. At the time of
the merger, each outstanding share of CogenAmerica common stock (other than
shares owned by CogenAmerica, by Calpine's acquisition subsidiary and by
stockholders who exercise their appraisal rights) will be converted into the
right to receive $25.00 per share in cash. After the merger, CogenAmerica will
no longer be publicly traded and will be owned 80% by Calpine and 20% by NRG
Energy, Inc., an existing stockholder of CogenAmerica. To review the structure
of the merger in greater detail, see pages                through
               of this proxy statement.

Q: Why does the CogenAmerica Board of Directors recommend the merger?

A: The CogenAmerica Board of Directors believes that the sale of CogenAmerica is
in your best interests by providing you the right to receive $25.00 per share in
cash for your shares of CogenAmerica common stock. To review the background of
and reasons for the merger in greater detail, see pages   through   of this
proxy statement.

Q: What will I receive in the merger?

A: You will have the right to receive $25.00 in cash, without interest, for each
share of CogenAmerica common stock that you own. For example, if you own 100
shares of CogenAmerica common stock, you will have the right to receive merger
consideration of $2,500.00 in cash upon completion of the merger.

Q: When do you expect the merger to be completed?

A: We are working to complete the merger by December 31, 1999.

Q: What are the tax consequences of the merger to me?

A: The merger will be a taxable transaction for federal income tax purposes to
CogenAmerica stockholders and option holders. To review the federal income tax
consequences to you in greater detail, see pages                through
               of this proxy statement. Your tax consequences will depend on
your personal situation. You should consult your tax advisor for a full
understanding of the tax consequences of the merger to you.

                                        1
<PAGE>   6

Q: What am I being asked to vote upon?

A: You are being asked to approve and adopt the merger agreement that provides
for the merger and the amendment to CogenAmerica's certificate of incorporation
that permits NRG to transfer a portion of its shares of CogenAmerica common
stock to Acquisition Sub which will allow NRG to retain a 20% interest in
CogenAmerica after the merger. The Board of Directors and the Independent
Directors Committee of CogenAmerica have unanimously approved the merger
agreement and the amendment, and recommend that the CogenAmerica stockholders
vote "FOR" the approval and adoption of the merger agreement and the amendment.

Q: What do I need to do now?

A: Simply indicate on your proxy card how you want to vote and then sign, date
and mail the proxy card in the enclosed envelope as soon as possible so that
your shares will be represented at the special meeting. In addition, you may
attend the special meeting and vote your shares in person, rather than voting by
proxy. You may withdraw your proxy up to and including the day of the special
meeting and either change your vote or attend the special meeting and vote in
person.

Q: If my shares are held in "street name" by my broker, will my broker vote my
shares for me?

A: Your broker will vote your shares only if you provide instructions on how to
vote. You should instruct your broker how to vote your shares by following the
directions your broker provides to you. If you do not provide instructions to
your broker, your shares will not be voted and they will be counted as votes
against the proposals to approve and adopt the merger agreement and the
amendment.

Q: Should I send in my stock certificates now?

A: No. After the merger is completed we will send you written instructions for
exchanging your CogenAmerica common stock certificates for the merger
consideration.

Q: Whom can I contact if I have additional questions or would like additional
copies of the proxy statement or proxy card?

A: You should contact:
                         Thomas L. Osteraas, Secretary
                         Cogeneration Corporation of America
                         One Carlson Parkway, Suite 240
                         Minneapolis, MN 55447-4454

                                        2
<PAGE>   7

                               TABLE OF CONTENTS

<TABLE>
<S>                                                             <C>
Summary.....................................................      1
  The Companies.............................................      1
  The Special Meeting.......................................      2
  Record Date; Voting Power; Votes Required.................      2
  Potential Benefits and Detriments of the Merger to
     Unaffiliated Stockholders; Benefits to Insiders........      3
  Recommendations of the Independent Directors Committee and
     the Board of Directors.................................      3
  Opinion of CogenAmerica's Financial Advisor...............      4
  Terms of the Merger Agreement.............................      4
     General................................................      4
     Conditions to the Merger...............................      4
     No Solicitation........................................      5
     Termination............................................      5
     Fees and Expenses......................................      5
  Accounting Treatment......................................      6
  Conflicts of Interests....................................      6
     Board of Directors and Officers of CogenAmerica........      6
     NRG....................................................      6
  Regulatory Approvals......................................      6
  Appraisal Rights..........................................      7
The Special Meeting.........................................      8
  General...................................................      8
  Proposals to be Considered at the Special Meeting.........      8
  Record Date; Voting Power; Votes Required.................      8
  Voting Procedures; Proxies................................      9
Historical Market Information...............................     10
Selected Consolidated Financial Data of CogenAmerica........     11
Proposal 1: The Merger......................................     12
Special Factors.............................................     12
  Background of the Merger..................................     12
  Purpose, Timing and Structure of the Merger...............     18
  Reasons for the Merger....................................     19
  Recommendations of the Independent Directors Committee and
     the Board of Directors.................................     23
  Opinion of Financial Advisor..............................     24
  Perspective of NRG on the Fairness of the Merger..........     29
  Plans for CogenAmerica After the Merger...................     29
  Certain Effects of the Merger.............................     30
  Unsolicited Offers From Third Parties.....................     30
  Conflicts of Interest.....................................     31
     Arrangements with NRG..................................     31
     Arrangements Between Calpine and NRG...................     32
     Directors and Officers of CogenAmerica.................     32
     Severance Agreements for Officers......................     33
     Indemnification........................................     33
Summary of Material Features of the Merger..................     35
  The Merger................................................     35
     General................................................     35
</TABLE>

                                        i
<PAGE>   8
<TABLE>
<S>                                                             <C>
     Merger Consideration...................................     35
     Payment for Shares.....................................     35
     Stock Options..........................................     35
     Closing of Transfer Books..............................     35
     Conditions to the Merger...............................     36
     Representations and Warranties.........................     37
     Certain Covenants......................................     37
     No Solicitation of Transactions........................     38
     Termination............................................     39
     Termination Fee........................................     40
     Indemnification........................................     40
     Amendment and Waiver...................................     41
     Expenses...............................................     41
  Effective Time............................................     41
  Conversion of Common Stock................................     41
  Payment for Stock Options.................................     42
  Conduct of Business Pending the Merger....................     42
  Regulatory Filings and Approvals..........................     42
  Conditions to the Merger..................................     42
  Federal Income Tax Consequences of the Transaction........     43
  Financing of the Merger; Source of Funds..................     43
  Anticipated Accounting Treatment..........................     43
  Appraisal Rights..........................................     44
Summary of Material Features of the Calpine/NRG Agreement...     48
Proposal 2: The Charter Amendment...........................     50
Summary of the Amendment....................................     50
Management of CogenAmerica..................................     50
Interest in Securities of CogenAmerica......................     50
Certain Transactions in Common Stock and Stock Options......     53
Expenses of the Transaction.................................     53
Independent Accountants.....................................     53
Where You Can Find More Information.........................     54
Incorporation of Certain Documents by Reference.............     55
Shareholder Proposals.......................................     55
Other Matters...............................................     55
Appendix to the Proxy Statement.............................     57
APPENDICES
APPENDIX A -- Agreement and Plan of Merger..................    A-1
APPENDIX B -- Amendment to CogenAmerica Certificate of
  Incorporation.............................................    B-1
APPENDIX C -- Opinion of Donaldson Lufkin & Jenrette
  Securities Corporation....................................    C-1
APPENDIX D -- Text of Section 262 of the Delaware General
  Corporation Law...........................................    D-1
</TABLE>

                                       ii
<PAGE>   9

                                    SUMMARY

     This summary highlights selected information from this proxy statement and
may not contain all of the information that is important to you. For a more
complete understanding of the merger and for a more complete description of the
legal terms of the merger, you should read this proxy statement carefully, as
well as the appendices to this proxy statement, including the merger agreement.
For additional information on CogenAmerica, see "Where You Can Find More
Information" (page   ).

THE COMPANIES

    Cogeneration Corporation of America
    One Carlson Parkway, Suite 240
    Minneapolis, Minnesota 55447-4454
    Telephone: (612) 745-7900

     Cogeneration Corporation of America, a Delaware corporation, is an
independent power producer engaged primarily in the business of developing,
owning and managing the operation of cogeneration projects which produce
electricity and thermal energy for sale under long-term contracts with
industrial and commercial users and public utilities. CogenAmerica's current
project portfolio consists of (1) a 122 megawatt ("MW") cogeneration facility in
Parlin, New Jersey, (2) a 58 MW cogeneration facility in Newark, New Jersey, (3)
a 117 MW cogeneration facility in Morris, Illinois, (4) a 110 MW cogeneration
facility in Pryor, Oklahoma, (5) an 83% interest in two standby/peak shaving
facilities with an aggregate capacity of 22 MW in Philadelphia, Pennsylvania,
and (6) a 50% interest in a 150 MW cogeneration facility in Philadelphia,
Pennsylvania. Through its United Kingdom subsidiary called Puma, CogenAmerica
also designs and assembles diesel and natural gas fueled power generation
systems ranging in size from 5 kilowatts to 5 MW. The CogenAmerica common stock
trades on the The Nasdaq Stock Market under the symbol "CGCA".

    Calpine Corporation
    50 West San Fernando Street
    San Jose, California 95113
    Telephone: (408) 995-0505

     Calpine Corporation, a Delaware corporation, is a leading independent power
company engaged in the development, acquisition, ownership and operation of
power generation facilities and the sale of electricity predominantly in the
United States.

    Calpine East Acquisition Corp.
    50 West San Fernando Street
    San Jose, California 95113
    Telephone: (408) 995-0505

     Calpine East Acquisition Corp., a Delaware corporation ("Acquisition Sub"),
is currently a wholly-owned subsidiary of Calpine. Calpine formed Acquisition
Sub shortly before execution of the merger agreement for the purpose of carrying
out the merger. Immediately prior to the merger NRG will contribute to
Acquisition Sub approximately

                                        1
<PAGE>   10

1.4 million shares of its CogenAmerica common stock in exchange for a 20%
interest in Acquisition Sub.

    NRG Energy, Inc.
    1221 Nicollet Mall, Suite 700
    Minneapolis, Minnesota 55403-2445
    Telephone: (612) 373-5300

     NRG Energy, Inc., a Delaware corporation, is one of the world's leading
independent power producers, specializing in the development, construction,
operation, maintenance and ownership of low-cost, environmentally sensitive
power plants. Established in 1989 as a wholly owned subsidiary of Northern
States Power Company, NRG has a diversified energy portfolio of projects in the
United States, Europe, the Pacific Rim, and Latin America. NRG is involved in
approximately 15,000 MW of projects utilizing diverse fuel types including
natural and landfill gas, hydro and solid fuels such as coal, lignite, biomass
and refuse-derived fuel.

THE SPECIAL MEETING (PAGE   )

     The special meeting will be held on December   , 1999 at 9:00 a.m., local
time, at [INSERT LOCATION OF THE SPECIAL MEETING]. At the special meeting,
stockholders will be asked to consider and vote upon a proposal to approve and
adopt the merger agreement and a proposal to approve the amendment to
CogenAmerica's certificate of incorporation. The special meeting has been called
by order of the CogenAmerica Board of Directors.

RECORD DATE; VOTING POWER; VOTES REQUIRED (PAGE   )

     Holders of record of CogenAmerica common stock at the close of business on
November   , 1999 are entitled to notice of and to vote at the special meeting.
As of that date, there were 6,857,269 shares of CogenAmerica common stock issued
and outstanding held by approximately 2,200 holders of record. Holders of record
of CogenAmerica common stock on the record date are entitled to one vote per
share on any matter that may properly come before the special meeting. The
quorum required to hold the special meeting is 60% of the shares of CogenAmerica
common stock entitled to vote at the meeting, present in person or by proxy. If
a quorum is present, the affirmative vote of the holders of more than 66 2/3% of
the outstanding shares of CogenAmerica common stock is required to approve and
adopt the merger agreement and the affirmative vote of the holders of more than
50% of the outstanding shares of CogenAmerica common stock is required to
approve the amendment to CogenAmerica's certificate of incorporation.

     On the record date, NRG owned 3,106,612 shares of CogenAmerica common stock
or approximately 45.3% of the outstanding shares. Pursuant to the contribution
and stockholder agreement dated as of August 26, 1999 (the "Calpine/NRG
Agreement") between NRG and Calpine, NRG has granted its proxy to Calpine to
vote the CogenAmerica shares held by NRG for approval and adoption of the merger
agreement and the charter amendment.

     If either proposal is not approved, the merger will not be completed,
CogenAmerica will remain a public company and the stockholders of CogenAmerica
will not have the right to receive $25.00 per share for the CogenAmerica common
stock. A stockholder who wishes to exercise appraisal rights under the Delaware
General Corporation Law

                                        2
<PAGE>   11

("DGCL") must vote against or fail to vote for approval and adoption of the
merger agreement.

POTENTIAL BENEFITS AND DETRIMENTS OF THE MERGER TO UNAFFILIATED STOCKHOLDERS;
BENEFITS TO INSIDERS (PAGES   ,   AND   )

     The primary benefit of the merger to you is the opportunity to sell all of
your shares of CogenAmerica common stock at a cash price which represents a
substantial premium over historical trading prices. The merger consideration of
$25.00 per share in cash represents a premium of approximately 48.6% over the
average market price for CogenAmerica common stock for the 20 trading days
preceding the announcement of the execution of the merger agreement on August
27, 1999. As a result of the merger, however, you will not be entitled to
participate in future earnings or growth of CogenAmerica. In addition, you will
be required to recognize a taxable gain as a result of the merger if your cost
basis in your shares of CogenAmerica common stock is less than $25.00 per share.

     Upon completion of the merger, Calpine will own 80% and NRG will own 20% of
the equity interests of CogenAmerica. As the stockholders of CogenAmerica,
Calpine and NRG will have complete control over the management and conduct of
CogenAmerica's business, all income generated by CogenAmerica and any future
increase in CogenAmerica's value. Similarly, Calpine and NRG will also bear the
risk of any losses incurred in the operation of CogenAmerica and any decrease in
the value of CogenAmerica. Calpine will have operating control over CogenAmerica
subject to certain limitations set forth in the Calpine/NRG Agreement.

     Like the unaffiliated stockholders of CogenAmerica, the executive officers
and directors of CogenAmerica will have the right to receive $25.00 per share
for each of their shares of CogenAmerica common stock. In addition, the officers
and directors of CogenAmerica who hold options will have the right to receive
(a) the excess of $25.00 over the exercise price of each option multiplied by
(b) the number of shares of CogenAmerica common stock purchasable upon exercise
of the option (after giving effect to any acceleration of the option as a result
of the merger), net of withholding and applicable taxes.

     At November   , 1999, the executive officers and directors of CogenAmerica
beneficially owned 737,000 shares of CogenAmerica common stock, including
647,000 shares subject to options that will become exercisable as a result of
the merger, representing an aggregate cash payment to such persons upon
completion of the merger of $9,482,625. Because current NRG corporate policy
prohibits NRG employees from receiving the economic benefit of options granted
to them in their capacity as a director of an affiliated company, the three NRG
employees, who currently serve as directors of CogenAmerica and were previously
granted stock options in their capacity as directors of CogenAmerica, have
agreed to cancel their stock options. The three NRG employees who serve as
directors of CogenAmerica will receive no cash payment for cancellation of these
options.

RECOMMENDATIONS OF THE INDEPENDENT DIRECTORS COMMITTEE AND THE BOARD OF
DIRECTORS (PAGE   )

     Because NRG will retain a 20% equity interest in CogenAmerica after the
merger and certain directors of CogenAmerica are or were officers of NRG, the
Independent Directors

                                        3
<PAGE>   12

Committee of the CogenAmerica Board of Directors reviewed and evaluated the
proposals to acquire CogenAmerica. At special meetings held on August 26, 1999,
the Independent Directors Committee and the Board of Directors of CogenAmerica
each unanimously determined that the merger is in furtherance of and consistent
with the long-term business strategies of CogenAmerica and is fair to and in the
best interest of the CogenAmerica stockholders (other than NRG). The
CogenAmerica Board of Directors unanimously recommends that you vote "FOR"
approval and adoption of the merger agreement and the charter amendment. You
should refer to the matters considered by the Independent Directors Committee
and the Board of Directors of CogenAmerica in determining whether to approve the
merger agreement, beginning at page   .

OPINION OF COGENAMERICA'S FINANCIAL ADVISOR (PAGE   )

     Donaldson, Lufkin & Jenrette Securities Corporation ("DLJ"), a nationally
recognized investment banking firm, rendered an opinion, dated August 26, 1999
to the Independent Directors Committee of the CogenAmerica Board of Directors
that, as of such date, based upon and subject to the assumptions, limitations
and qualifications in the opinion, the consideration to be received by the
holders (other than NRG) of CogenAmerica common stock in the merger is fair to
the holders from a financial point of view. THE FULL TEXT OF THE WRITTEN OPINION
OF DLJ IS ATTACHED TO THIS PROXY STATEMENT AS APPENDIX C. YOU SHOULD READ THE
FAIRNESS OPINION OF DLJ IN ITS ENTIRETY.

TERMS OF THE MERGER AGREEMENT (PAGE   )

     The merger agreement is attached to this proxy statement as Appendix A. You
should read the merger agreement in its entirety. It is the legal document that
governs the merger.

     General. The merger agreement provides that Acquisition Sub will be merged
into CogenAmerica and CogenAmerica will be the surviving corporation. As a
result of the merger, the stockholders of CogenAmerica will have the right to
receive $25.00 in cash, without interest, for each share of common stock that
they own, other than shares owned by CogenAmerica, Acquisition Sub or
CogenAmerica stockholders who exercise their appraisal rights.

     Conditions to the Merger. The completion of the merger depends upon the
satisfaction of a number of conditions, including:

     - approval of the merger agreement by the holders of more than 66 2/3% of
       the outstanding shares of common stock;

     - approval of the charter amendment by the holders of more than 50% of the
       outstanding shares of CogenAmerica common stock;

     - receipt of all necessary orders and consents of governmental authorities
       and other persons and the expiration of any regulatory waiting periods;

     - material accuracy of the representations and warranties of the parties
       and the fulfillment of each party's promises contained in the merger
       agreement;

     - absence of any court or governmental entity rendering the merger illegal;
       and

     - absence of litigation having a material adverse effect on CogenAmerica.

                                        4
<PAGE>   13

     Each party may waive the satisfaction of any condition to its obligations
under the merger agreement, other than approval of the merger agreement and the
charter amendment by the CogenAmerica stockholders. EVEN IF THE COGENAMERICA
STOCKHOLDERS APPROVE THE MERGER AGREEMENT, THERE CAN BE NO ASSURANCE THAT THE
CONDITIONS TO THE OBLIGATIONS OF THE PARTIES TO COMPLETE THE MERGER WILL BE MET
OR WAIVED OR THAT THE MERGER WILL BE COMPLETED.

     No Solicitation. Until completion or abandonment of the merger,
CogenAmerica and its affiliates are not permitted to solicit, initiate or
encourage any acquisition proposals from any other party. CogenAmerica may
respond to unsolicited acquisition proposals and enter into discussions if,
after receiving advice of counsel, the CogenAmerica Board of Directors
determines such response is necessary to fulfill its fiduciary obligations and
such proposal provides for consideration to CogenAmerica stockholders that is
superior to the consideration to CogenAmerica stockholders under the merger
agreement.

     Termination. Either CogenAmerica or Calpine may terminate the merger
agreement under certain circumstances, including if:

          - CogenAmerica and Calpine mutually consent in writing;

          - the merger is not completed by the close of business on February 28,
            2000 or, if the special meeting has not been held by February 28,
            2000, then the merger is not completed by the close of business on
            March 31, 2000;

          - legal constraints or prohibitions prevent the completion of the
            merger;

          - CogenAmerica stockholders do not approve the merger agreement and
            the charter amendment;

          - the other party breaches in a material manner any of its
            representations, warranties or covenants under the merger agreement
            and the breach is not cured within 30 business days after notice; or

          - CogenAmerica enters into or the CogenAmerica Board of Directors
            approves an agreement for CogenAmerica to be acquired by another
            party for consideration to CogenAmerica stockholders that is
            superior to the consideration to CogenAmerica stockholders under the
            merger agreement (a "Superior Proposal") so long as (a) CogenAmerica
            notifies Calpine of the Superior Proposal, (b) Calpine has an
            opportunity to respond, and (c) CogenAmerica pays Calpine a
            termination fee of $7,500,000.

     In addition, Calpine may terminate the merger agreement if the CogenAmerica
Board of Directors withdraws or modifies its recommendation that CogenAmerica
stockholders approve the merger agreement, or recommends an alternative
acquisition proposal.

     Fees and Expenses. Each of CogenAmerica, Calpine and Acquisition Sub agreed
to pay its own fees and expenses. CogenAmerica will pay a termination fee of
$7,500,000 to Calpine if the merger agreement is terminated by reason of a
superior proposal permitting termination of the merger agreement or if
CogenAmerica is acquired by another party within 12 months following termination
of the merger agreement under certain circumstances specified in the merger
agreement.

                                        5
<PAGE>   14

ACCOUNTING TREATMENT (PAGE      )

     CogenAmerica believes that the merger will be accounted for by Acquisition
Sub using the purchase method of accounting in accordance with generally
accepted accounting principles.

CONFLICTS OF INTERESTS (PAGE      )

     Board of Directors and Officers of Cogenamerica. Four members of the
CogenAmerica Board of Directors were, at the time the CogenAmerica Board of
Directors approved the merger agreement, officers of NRG. However, none of the
NRG officers on the Board of Directors were members of the Independent Directors
Committee. Because current NRG corporate policy prohibits NRG employees from
receiving the economic benefit of options granted to them in their capacity as a
director of an affiliated company, the NRG employees, who currently serve as
directors of CogenAmerica and were previously granted stock options in their
capacity as directors of CogenAmerica, have agreed to the cancellation of their
stock options. The NRG employees who serve as directors of CogenAmerica will
receive no cash payment for cancellation of these options. The officers of
CogenAmerica, including its President and Chief Executive Officer who is also a
director of CogenAmerica, own or have options to purchase a substantial number
of shares of CogenAmerica common stock. All three disinterested directors of
CogenAmerica who comprise the Independent Director Committee own or have options
to purchase a substantial number of shares of CogenAmerica common stock.

     NRG. As of the close of business on November   , 1999, NRG beneficially
owned 3,106,612 shares of CogenAmerica common stock which represents
approximately 45.3% of the outstanding shares. Pursuant to the Calpine/NRG
Agreement, NRG has agreed to contribute immediately prior to completion of the
merger part of its holdings (approximately 1.4 million shares of common stock)
to Acquisition Sub in exchange for a 20% interest in Acquisition Sub. NRG has
granted its proxy to Calpine to vote the CogenAmerica shares held by NRG for
approval and adoption of the merger agreement and the charter amendment at the
special meeting. In addition, NRG or its subsidiaries and CogenAmerica or its
subsidiaries are currently parties to agreements (the "Affiliate Agreements")
pursuant to which (1) NRG has agreed to offer to sell to CogenAmerica certain
independent power plants developed by NRG, (2) NRG has agreed to provide certain
management services to CogenAmerica and CogenAmerica has agreed to reimburse NRG
for its costs incurred to provide the management services, and (3) NRG manages
the operation of independent power plants owned by CogenAmerica in Morris,
Illinois, and in Newark and Parlin, New Jersey, and CogenAmerica pays NRG
certain management fees and reimburses NRG for its operating costs. In
connection with the completion of the merger, NRG and CogenAmerica will
terminate these agreements and exchange mutual general releases.

REGULATORY APPROVALS (PAGE      )

     CogenAmerica is required to make filings with or obtain approvals from
regulatory authorities in connection with the merger. These filings and
approvals include filings with the Securities and Exchange Commission (the
"SEC"), the Federal Trade Commission, the Department of Justice, the Federal
Energy Regulatory Commission ("FERC") and the New Jersey Department of
Environmental Protection. The filings with the SEC consist

                                        6
<PAGE>   15

of this proxy statement and a Schedule 13E-3 providing certain disclosures to
CogenAmerica stockholders concerning the merger and the parties to the
transactions contemplated by the merger agreement. An application and notice was
filed with the Federal Trade Commission and the Department of Justice as
required by the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended
(the "HSR Act") on September   , 1999. An application and notice was filed with
the FERC on September 17, 1999. The requisite filings under the New Jersey
Industrial Site Recovery Act were made on August 31, 1999.

APPRAISAL RIGHTS (PAGE      )

     Any stockholder of CogenAmerica who does not vote in favor of the proposal
to approve the merger agreement and who strictly complies with the applicable
provisions of Section 262 of the DGCL has appraisal rights to receive cash for
the "fair value" for such holder's shares of CogenAmerica common stock, which
may be more than, the same as, or less than the agreed consideration of $25.00
per share. "Fair value" will be determined based on the value of the shares
immediately before completion of the merger without any appreciation or
depreciation in anticipation of the merger and may be more than, the same or
less than the merger consideration of $25.00 per share. To exercise appraisal
rights with respect to the merger, you must follow the required procedures
precisely, which include the requirement to give written notice to CogenAmerica
before the special meeting of your intent to demand payment. A stockholder who
wishes to exercise appraisal rights under the DGCL must vote against or fail to
vote for approval and adoption of the merger agreement. The provisions of
Section 262 of the DGCL are attached to this proxy statement as Appendix D.

                                        7
<PAGE>   16

                              THE SPECIAL MEETING

GENERAL

     This proxy statement is furnished in connection with the solicitation of
proxies by the CogenAmerica Board of Directors for the special meeting of
Stockholders of CogenAmerica to be held on December   , 1999 at 9:00 a.m., local
time, at [INSERT LOCATION OF SPECIAL MEETING] and at any adjournments thereof.

PROPOSALS TO BE CONSIDERED AT THE SPECIAL MEETING

     At the special meeting, the CogenAmerica stockholders will be asked to
consider and vote upon:

     - a proposal to approve and adopt the merger agreement,

     - a proposal to approve and adopt the charter amendment, and

     - consider and act upon such other matters as may properly come before the
       special meeting.

     The merger is conditioned on the approval of the merger agreement and the
charter amendment by the CogenAmerica stockholders. Subject to the receipt of
regulatory approvals, approval by the CogenAmerica stockholders and satisfaction
of other conditions, the merger agreement provides for the merger of Acquisition
Sub with and into CogenAmerica. If the proposed merger is completed, each issued
and outstanding share of CogenAmerica common stock at the effective time of the
merger (other than shares owned by CogenAmerica, by Acquisition Sub and by
stockholders who exercise their appraisal rights) will be converted into the
right to receive $25.00 in cash. The charter amendment enables NRG to transfer
and contribute to Acquisition Sub immediately prior to completion of the merger
approximately 1.4 million shares of its CogenAmerica common stock in exchange
for a 20% equity interest in Acquisition Sub. After completion of the merger,
CogenAmerica will be owned 80% by Calpine and 20% by NRG.

RECORD DATE; VOTING POWER; VOTES REQUIRED

     Only holders of record of CogenAmerica common stock on the record date are
entitled to notice of and to vote at the special meeting. As of November   ,
1999, there were 6,857,269 shares of CogenAmerica common stock issued and
outstanding and held by approximately 2,200 holders of record. Holders of record
of CogenAmerica common stock on the record date are entitled to one vote per
share on any matter that may properly come before the special meeting. The
quorum required to hold the special meeting is 60% of the shares of CogenAmerica
common stock entitled to vote at the meeting, present in person or by proxy. If
a quorum is present, the affirmative vote of the holders of more than 66 2/3% of
the total voting power of the shares of CogenAmerica common stock entitled to
vote is required to approve and adopt the merger agreement, and the affirmative
vote of the holders of more than 50% of the shares of CogenAmerica common stock
entitled to vote is required to approve the charter amendment.

     On the record date, NRG owned 3,106,612 shares of CogenAmerica common stock
or approximately 45.3% of the outstanding shares. Pursuant to the Calpine/NRG
Agreement, NRG granted its proxy to Calpine to vote the CogenAmerica shares held
by NRG for approval and adoption of the merger agreement and the charter
amendment. Accordingly,

                                        8
<PAGE>   17

CogenAmerica needs the affirmative vote of an additional 1,464,901 shares to
approve and adopt the merger agreement and 322,023 shares to approve the charter
amendment.

VOTING PROCEDURES; PROXIES

     If you fail to vote, or vote to abstain, it will have the same legal effect
as a vote cast against the proposals. Your broker and, in many cases, your
nominee will not have discretionary power to vote on the proposals to be
presented at the special meeting. Accordingly, you should instruct your broker
or nominee how to vote. A broker non-vote will have the same effect as a vote
against the proposals.

     If there are insufficient votes to approve the proposals at the special
meeting and if you voted in favor of the merger agreement and the charter
amendment, your proxy may be voted to adjourn the special meeting in order to
solicit additional proxies in favor of the proposals. If the special meeting is
adjourned or postponed for any purpose, at any subsequent reconvening of the
special meeting, your proxy will be voted in the same manner as it would have
been voted at the original convening of the meeting unless you withdraw or
revoke your proxy. Your proxy may be voted this way even though it may have been
voted on the same or any other matter at a previous meeting.

     Under Delaware law, if you do not vote in favor of the proposals and comply
with certain notice requirements and other procedures, you will have the right
to dissent and to be paid cash for the "fair value" of your shares as finally
determined under such procedures. This payment may be more, the same as or less
than the consideration to be received by other CogenAmerica stockholders under
the terms of the merger agreement. If you fail to follow such procedures
precisely, you may lose your appraisal rights. See "Appraisal Rights."

     Each stockholder who signs and returns a proxy in the form enclosed with
this proxy statement may revoke the same at any time prior to its use by giving
notice of such revocation to CogenAmerica in writing or in person at the special
meeting. Signing and returning a later dated proxy in the form enclosed with
this proxy statement will revoke a prior proxy. Presence at the special meeting
of a stockholder who has signed a proxy does not alone revoke that proxy. Unless
so revoked, all of the shares represented by each proxy will be voted at the
special meeting and at any adjournments thereof. IF NO INSTRUCTIONS ARE
INDICATED, SUCH PROXIES WILL BE VOTED FOR THE PROPOSALS TO APPROVE AND ADOPT THE
MERGER AGREEMENT AND THE CHARTER AMENDMENT, FOR POSTPONEMENT OR ADJOURNING OF
THE SPECIAL MEETING FOR THE PURPOSE OF SOLICITING ADDITIONAL PROXIES FOR
APPROVAL AND ADOPTION OF THE MERGER AGREEMENT, THE CHARTER AMENDMENT AND, IN THE
DISCRETION OF THE PERSONS NAMED ON THE PROXY, ON SUCH OTHER MATTERS AS MAY
PROPERLY BE PRESENTED AT THE SPECIAL MEETING.

     The cost of preparing, assembling and mailing this proxy statement, the
notice, the proxy card and other material which may be sent to the stockholders
will be borne by CogenAmerica. In addition, directors, officers and regular
employees of CogenAmerica and its subsidiaries, at no additional compensation,
may solicit proxies by telephone, telegram or in person. Upon request,
CogenAmerica will reimburse brokers and other persons holding shares for the
benefit of others for their expenses in forwarding proxies and accompanying
material and in obtaining authorization from beneficial owners of CogenAmerica
common stock to give proxies.

                                        9
<PAGE>   18

     In order to assure the presence of the necessary quorum at the special
meeting, please sign and mail the enclosed proxy promptly in the envelope
provided. No postage is required if mailed within the United States. The signing
of the proxy will not prevent you from attending the meeting and voting in
person, should you so desire.

                         HISTORICAL MARKET INFORMATION

     CogenAmerica common stock is currently traded on Nasdaq National Market
tier of The Nasdaq Stock Market under the symbol "CGCA". From March 1997 to
November 1997, the CogenAmerica common stock was traded on the Nasdaq SmallCap
Market. Prior to March 1997, the CogenAmerica common stock was not listed on an
exchange or on The Nasdaq Stock Market, but traded from time to time on the pink
sheets and on the OTC Bulletin Board. The following table sets forth the high
and low sales prices for each quarterly period since 1997 from the quotations
published by Nasdaq-Amex Online. Such prices may have reflected inter-dealer
prices, without retail mark-ups, mark-downs or commissions, and may not
necessarily represent actual transactions.

<TABLE>
<CAPTION>
                                                                 HIGH        LOW
                                                                -------    -------
<S>                                                             <C>        <C>
1999:
First Quarter...............................................    $ 9.375    $  8.00
Second Quarter..............................................    $ 14.50    $ 8.125
Third Quarter...............................................    $          $
Fourth Quarter (through November   , 1999)..................    $          $

1998:
First Quarter...............................................    $19.531    $15.125
Second Quarter..............................................    $ 18.25    $13.313
Third Quarter...............................................    $ 15.00    $  7.25
Fourth Quarter..............................................    $ 10.00    $ 7.625

1997:
First Quarter...............................................    $ 13.75    $ 11.25
Second Quarter..............................................    $ 16.00    $11.125
Third Quarter...............................................    $ 21.00    $ 14.25
Fourth Quarter..............................................    $22.375    $ 18.00
</TABLE>

     On August 26, 1999, the last trading day prior to announcement of the
execution of the merger agreement, the closing sale price per share of
CogenAmerica common stock on The Nasdaq Stock Market as published by Nasdaq-Amex
Online was $16.813. On November   , 1999, the closing sale price per share of
CogenAmerica common stock was $          . The high and low bid quotations
during the period from August 26, 1999 (the date the merger was announced)
through November   , 1999 were $          and $          , respectively.

     CogenAmerica has not paid any cash dividends on its common stock.

                                       10
<PAGE>   19

              SELECTED CONSOLIDATED FINANCIAL DATA OF COGENAMERICA

     The following table shows summarized historical financial data for
CogenAmerica. This information is based on historical information presented in
CogenAmerica's filings with the SEC. You should read all of the summary
financial information in the table in connection with this historical financial
information. This historical financial information is incorporated into this
proxy statement by reference. See "Where You Can Find More Information" on page
  . Effective December 31, 1996, CogenAmerica changed its fiscal year end from
June 30 to December 31.

<TABLE>
<CAPTION>
                       SIX MONTHS   SIX MONTHS       YEAR           YEAR        SIX MONTHS      YEAR       YEAR       YEAR
                         ENDED        ENDED         ENDED          ENDED          ENDED        ENDED      ENDED      ENDED
                        JUNE 30,     JUNE 30,    DECEMBER 31,   DECEMBER 31,   DECEMBER 31,   JUNE 30,   JUNE 30,   JUNE 30,
                          1999         1998          1998           1997         1996(1)        1996       1995       1994
                       ----------   ----------   ------------   ------------   ------------   --------   --------   --------
                                                 (DOLLARS IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
<S>                    <C>          <C>          <C>            <C>            <C>            <C>        <C>        <C>
STATEMENT OF
  OPERATIONS DATA:
Revenues:
Energy...............   $ 45,302     $ 21,801      $ 52,216       $ 43,210       $ 21,669     $ 66,623   $ 74,455   $ 62,647
Equipment sales and
  services...........      7,096        8,334        19,342         19,415         15,607       25,344     19,639     24,304
Rental...............         --        1,481         2,438          2,179          1,062        1,895      2,362      5,372
Development fees and
  other..............         --           --            --             --          1,578        2,685      5,791     14,266
    Total............     52,398       31,616        73,996         64,804         39,916       96,547    102,247    106,589
Income (loss) before
  extraordinary
  item...............     12,816        4,052         8,002         23,352          4,780      (17,713)   (40,919)   (16,501)
Net income
  (loss)(4)..........     12,816        4,052         8,002         23,352          6,423      (17,713)   (40,919)   (16,501)
Basic earnings (loss)
  per share(2):
  Before
    extraordinary
    Item.............   $   1.87     $   0.59      $   1.17       $   3.59       $   0.75     $  (4.24)  $ (11.02)  $  (4.45)
  Extraordinary
    item.............         --           --            --             --           0.25           --         --         --
  After extraordinary
    Item.............   $   1.87     $   0.59      $   1.17       $   3.59       $   1.00     $  (4.24)  $ (11.02)  $  (4.45)
Diluted earnings
  (loss) per
  share(2):
  Before
    extraordinary
    Item.............   $   1.85     $   0.58      $   1.15       $   3.48       $   0.74     $  (4.24)  $ (11.02)  $  (4.45)
  Extraordinary
    item.............         --           --            --             --           0.25           --         --         --
  After extraordinary
    Item.............   $   1.85     $   0.58      $   1.15       $   3.48       $   0.99     $  (4.24)  $ (11.02)  $  (4.45)
BALANCE SHEET DATA:
    Total assets.....   $341,612     $263,178      $318,674       $227,894       $173,624     $178,162   $189,748   $237,816
Long-term debt, net
  of current
  maturities:
  Loans due NRG......     40,123        4,439        36,123          4,439         14,388       96,929         --         --
  Nonrecourse long-
    term debt(3).....    186,810      201,077       189,848        143,697        143,972       60,415      3,405     60,310
  Recourse long-term
    debt.............     45,225       25,000        45,225         46,323          6,339        6,374         --      7,073
    Total............    272,158      230,516       271,196        194,459        164,699      163,718      3,405     67,383
</TABLE>

- ---------------

(1) Effective July 1, 1996, CogenAmerica changed its fiscal year-end from June
    30 to December 31.

(2) Net income (loss) per share has been restated for all periods presented to
    reflect the common shares issued under the terms of the plan of
    reorganization for O'Brien Environmental Energy, Inc. (now called
    Cogeneration Corporation of America) which emerged from reorganization under
    Chapter 11 of the Federal bankruptcy laws on April 30, 1996.

(3) Amount at June 30, 1995 excludes $60,310 of long-term project financing
    which was included in current liabilities due to a default under the debt
    agreement.

(4) Amount for 1997 reflects a net tax benefit of $20,454 resulting from the
    reduction of a tax valuation allowance. See Note 16 of CogenAmerica's
    Consolidated Financial Statements incorporated by reference into this proxy
    statement.

                                       11
<PAGE>   20

                             PROPOSAL 1: THE MERGER

                                SPECIAL FACTORS

BACKGROUND OF THE MERGER

     CogenAmerica's predecessor, O'Brien Environmental Energy, Inc., filed for
protection under Chapter 11 of the Federal bankruptcy laws on September 28,
1994. NRG proposed a plan of reorganization that was approved by the Bankruptcy
Court and O'Brien emerged from bankruptcy on April 30, 1996 under the name NRG
Generating (U.S.) Inc. ("NRG Generating") which subsequently changed its name to
Cogeneration Corporation of America. Under the reorganization plan, NRG advanced
NRG Generating $71.2 million under loan agreements, purchased approximately
41.86% of the NRG Generating common stock for approximately $21.2 million,
purchased certain subsidiaries of NRG Generating for $7.5 million and funded a
cash distribution to the former O'Brien stockholders totaling $7.5 million. The
former O'Brien stockholders also retained the remaining common stock or
approximately 58.14% of the then outstanding shares that were publicly traded.
In addition, as part of the reorganization plan, NRG and NRG Generating entered
into a co-investment agreement under which NRG agreed to offer NRG Generating
ownership interests in certain power projects that NRG initially developed or
had the right under contract to acquire from a third party and a management
services agreement under which NRG agreed to provide, at its cost, management
and support services. Pursuant to the co-investment agreement, CogenAmerica
acquired from NRG the Pryor, Oklahoma plant for $23.9 million in 1998 and the
Morris, Illinois plant for a development fee of $4.8 million paid to NRG plus
assumption of liabilities related to the project in 1997. Because of NRG's
substantial ownership of CogenAmerica and the number of NRG representatives on
the CogenAmerica Board of Directors, the new bylaws for CogenAmerica approved as
part of the bankruptcy reorganization plan established an Independent Directors
Committee of the Board of Directors that is responsible for making all decisions
for CogenAmerica in connection with the co-investment agreement and the
management services agreement with NRG. Under the bylaws, the Independent
Directors Committee must consist of at least two disinterested directors.
Currently, the Independent Directors Committee is comprised of the three
disinterested directors on the CogenAmerica Board of Directors, Mark Liddell,
Lawrence I. Littman, and Charles J. Thayer.

     From January 26, 1999 through May 13, 1999, CogenAmerica received
indications of interest from four independent power companies, including Calpine
and Bidder A, to acquire 100% of the equity interests of CogenAmerica. The bids
ranged from $16.00 to $19.00 per share in cash. During this period, the range of
the public trading prices for CogenAmerica common stock was $8.00 to $13.00 per
share.

     Based on the level of interest from the four parties and the significant
premium in their indications of interest over the then market price of the
CogenAmerica common stock, management informed the CogenAmerica Board of
Directors of the indications of interest and sought advice from financial and
legal advisors on how best to proceed in considering the offers. Management
contacted DLJ since DLJ had previously served as CogenAmerica's investment
banker and was familiar with CogenAmerica's business and the independent power
and public utility industries. Management also sought advice from Kaplan,
Strangis and Kaplan, P.A. ("KSK"), a Minneapolis, Minnesota law firm experienced
in acquisition and merger transactions. Copies of the indications of interest
from the four parties were also provided to the directors of CogenAmerica. Based
upon the

                                       12
<PAGE>   21

advice of DLJ and KSK, and after the directors had reviewed that advice and
considered their alternatives, a meeting of the CogenAmerica Board of Directors
was scheduled for May 20, 1999.

     At the meeting of the CogenAmerica Board of Directors on May 20, 1999, the
directors reviewed the indications of interest, counsel explained the fiduciary
duties of the CogenAmerica Board of Directors under the circumstances and DLJ
provided a presentation on current industry conditions and the strategic
alternatives available to the CogenAmerica Board of Directors. The CogenAmerica
Board of Directors determined that a sale of 100% of the equity interests of
CogenAmerica should be explored, approved the engagement of DLJ and KSK, and
authorized DLJ to assist management and counsel in the conduct of a process for
the sale of CogenAmerica.

     Following the May 20, 1999 CogenAmerica Board of Directors meeting, DLJ
assisted management in preparing an "Information Package" to provide interested
parties with relevant information on CogenAmerica and its business, assets,
operations and personnel. The Information Package consisted of (i) the Annual
Report of CogenAmerica for the year ended December 31, 1998; (ii) the Quarterly
Report on form 10-Q of CogenAmerica for the Quarter ended March 31, 1999; (iii)
the Proxy Statement dated April 26, 1999 for CogenAmerica's annual stockholders
meeting; and (iv) a financial model based on management's internal projections
for each of CogenAmerica's existing six plants and consolidated statements for
CogenAmerica for the period from January 1, 1999 to December 31, 2009. From May
25, 1999 through June 4, 1999, DLJ contacted 13 parties in the independent power
industry or the public utility industry that had the financial resources to
acquire CogenAmerica and that had been active in acquiring generation capacity.
Nine of the 13 parties indicated an interest in reviewing the Information
Package for CogenAmerica, including Calpine and Bidder A. CogenAmerica executed
confidentiality agreements with each of the eight bidders that had not
previously executed a confidentiality agreement. After each bidder had signed a
confidentiality agreement, it received an Information Package. After receiving
the Information Package, the nine parties were requested to submit preliminary
bids on June 11, 1999. Seven parties submitted preliminary indications of
interest, while two parties declined to submit indications of interest. The
preliminary indications of interest ranged from a low of $15.09 per share to a
high of $24.00 per share for 100% of the equity interests in CogenAmerica. On
June 11, 1999, DLJ received an unsolicited indication of interest from an
investment fund for an acquisition of CogenAmerica.

     On June 21, 1999, the CogenAmerica Board of Directors met to consider the
preliminary indications of interest. DLJ summarized the current status of the
solicitation process and described the terms of each preliminary bid. DLJ also
advised the CogenAmerica Board of Directors that an investment fund had
approached DLJ with an unsolicited indication of interest in acquiring
CogenAmerica. The CogenAmerica Board of Directors decided to continue the sale
process with the five highest bidders and the investment fund upon its execution
of a confidentiality agreement. Continuation of the sale process included
allowing the six bidders access to CogenAmerica's management and records for
purposes of conducting due diligence. The CogenAmerica Board of Directors
established July 13, 1999 as the date on which the six remaining parties would
be required to submit firm offers. The CogenAmerica Board of Directors also
decided to invite the highest bidder from the June 11 round of bids to make a
preemptive bid.

     The due diligence process included an opportunity to review of the
corporate, legal and financial records of CogenAmerica, including material
contracts, and a management

                                       13
<PAGE>   22

presentation with an opportunity to ask questions of management. Each
prospective bidder was also provided forms of merger agreement with CogenAmerica
and a stockholder agreement with NRG that had been prepared by CogenAmerica's
outside counsel with the input of management and NRG, and approved by
CogenAmerica and NRG. The highest bidder in the June 11, 1999 round of bids
declined to submit a preemptive offer. On July 13, 1999, the six parties
submitted their bids and comments on the proposed forms of merger agreement and
stockholder agreement. The cash bids ranged from a low of $18.50 per share to a
high of $23.00 per share. All of the bids also required CogenAmerica and NRG to
terminate the Affiliate Agreements.

     On July 15, 1999, the CogenAmerica Board of Directors met to consider the
bids. DLJ summarized the current status of the solicitation process and
described the terms of each bid. Counsel reviewed the changes proposed by the
bidders to the forms of merger agreement and stockholder agreement. In this
round, Calpine and Bidder A were the highest bidders with bids of $22.50 per
share and $23.00 per share, respectively. The CogenAmerica Board of Directors
determined that negotiations should proceed with Calpine and Bidder A on the
terms of the merger agreement and the stockholder agreement and that each party
should complete its due diligence.

     Later that day, Calpine and Bidder A were notified that they were the two
final bidders in the sale process and that their bids were virtually equal.
Subsequently, representatives of NRG indicated to CogenAmerica's management and
outside counsel that NRG might not be able to sell all of its equity interest in
CogenAmerica in light of the pending merger transaction involving NRG's parent
company, Northern States Power Company ("NSP") which effectively limits the
disposition of assets by parties to the merger. As a result, meetings of the
Independent Directors Committee and the Board of Directors of CogenAmerica were
scheduled for July 22, 1999.

     A meeting of the Independent Directors Committee was held by telephone on
July 22, 1999 followed by a meeting of the CogenAmerica Board of Directors. DLJ
briefed the independent directors on the status of discussions with the
remaining two bidders. Counsel apprised the Independent Directors Committee of
the issue that NRG had raised and that resolution of the issue might require a
different transaction structure. Counsel also updated the Independent Directors
Committee on the progress of negotiations with NRG on the terms of an agreement
pursuant to which the various contracts with NRG and its subsidiaries would be
terminated in the event of a sale of CogenAmerica. The Independent Directors
Committee and the Board of Directors of CogenAmerica determined that the new
concerns regarding the transaction structure should be resolved as quickly as
possible and that the sale process with the remaining two bidders should
proceed.

     On July 27, 1999, representatives from Calpine and its counsel met with
representatives of CogenAmerica and its management to negotiate Calpine's
proposed changes to the form of merger agreement. Thereafter, NRG's
representatives, with CogenAmerica's management and representatives present,
negotiated with Calpine its proposed changes to the form of stockholder
agreement with NRG. On July 28, 1999, representatives from Bidder A and its
counsel met with representatives of CogenAmerica and its management to negotiate
Bidder A's proposed changes to the form of merger agreement. Thereafter, NRG's
representatives, with CogenAmerica's management and representatives present,
negotiated with Bidder A its proposed changes to the form of stockholder
agreement with NRG. At each meeting, counsel for CogenAmerica informed Calpine
and Bidder A of the possibility of an alternative transaction structure. Both
parties were willing to proceed with the sale process while a viable transaction
structure was developed. Based on the

                                       14
<PAGE>   23

negotiating sessions over the definitive agreements, CogenAmerica delivered to
Calpine and Bidder A on or about July 30, 1999 revised forms of the merger
agreement and stockholder agreement that were acceptable to CogenAmerica. The
parties were requested to submit revised bids and any revisions to the merger
agreement and the stockholder agreement by August 3, 1999.

     On August 3, 1999, both Calpine and Bidder A submitted new bids, including
a mark-up of the merger agreement and stockholder agreement that each party was
willing to execute. Calpine initially offered $23.52 per share in cash for 100%
of the equity interests of CogenAmerica and Bidder A offered $24.00 per share in
cash for 100% of the equity interests in CogenAmerica. A meeting of the
CogenAmerica Board of Directors was held on August 4, 1999 to consider the bids.
Shortly before the meeting, Calpine increased its bid to $24.52 per share in
cash. At the meeting, DLJ summarized the sale process to date and confirmed its
view that either party had the requisite financial resources available to
consummate the transaction. Counsel described the material changes proposed by
Calpine and Bidder A to the merger agreement and stockholder agreement. NRG's
representative informed the CogenAmerica Board of Directors that the transaction
would have to be restructured to meet NRG's needs if a transaction were to
proceed. The CogenAmerica Board of Directors then determined that the
Independent Directors Committee should be given full control of the sale process
because NRG might have interests that differ from those of CogenAmerica and the
unaffiliated stockholders. The Independent Directors Committee met briefly and
requested that NRG outline the proposed structure of the transaction before
requiring the two remaining bidders to submit final bids. The full CogenAmerica
Board of Directors meeting then reconvened and the CogenAmerica Board of
Directors was apprised of the determinations by the Independent Directors
Committee.

     On August 6, 1999, the Independent Directors Committee held a meeting to
determine how to proceed. Counsel reviewed the outline of the possible
transaction structure developed by NRG's representatives, which remained subject
to approval by NRG's board of directors and advised the committee members that
an outline of the proposed transaction could be provided to the two bidders
later that day. The outline proposed that the winning bidder would have the
right to acquire 80% of the equity interests in CogenAmerica and NRG would
retain a 20% equity interest in CogenAmerica. Counsel confirmed that, as a
result of the restructuring of the proposed transaction, NRG did in fact have
interests that differed from those of CogenAmerica and the unaffiliated
stockholders.

     Later that day, the two bidders received the outline of the proposed
structure of the transaction. Each of the bidders was also advised that it would
have an opportunity to discuss and negotiate the proposed terms of a possible
transaction with NRG and that each bidder would be required to resubmit its bid
for CogenAmerica by the close of business on August 10, 1999. On Monday, August
9, 1999, each party separately reviewed and negotiated the terms of a possible
transaction with NRG representatives. Representatives of DLJ and KSK were
present during such discussions.

     At the close of business on August 10, 1999, both Calpine and Bidder A
resubmitted their respective bids. Each party provided a mark-up of the merger
agreement previously provided by CogenAmerica to reflect the changes required by
it and a mark-up of the outline of the possible transaction structure. Neither
party changed the price per share in its bid; Calpine offered $24.52 per share
in cash and Bidder A offered $24.00 per share in cash for 80% of the equity
interests in CogenAmerica.

                                       15
<PAGE>   24

     On August 11 and 12, 1999, the Independent Directors Committee held
telephonic meetings. At each meeting, DLJ reported on the rebids received from
the two bidders and counsel summarized the changes to the merger agreement
proposed by each Bidder And reported the status of the continuing discussions
between NRG and each bidder. Following the meetings, at the direction of the
Independent Directors Committee, DLJ communicated with both bidders
contemporaneously. Bidder A was informed that it needed to increase its bid and
Calpine was advised that it needed to accept the merger agreement as proposed by
CogenAmerica and the outline as acceptable to NRG's management which remained
subject to approval by NRG's board of directors.

     In the evening of August 12, 1999, Calpine delivered a letter to
CogenAmerica increasing its offer to $24.77 per share in cash, accepting the
merger agreement as proposed by CogenAmerica, accepting the terms acceptable to
NRG's management, which remained subject to approval by NRG's board of
directors, and indicating its willingness to negotiate and finalize definitive
documents on such terms. Calpine stated that its offer required an exclusive
period through 5:00 p.m. Eastern Time on August 17, 1999 to finalize the
documentation with NRG.

     On August 13, 1999, commencing at approximately 6:00 a.m., Central Time,
the Independent Directors Committee held a telephonic meeting. The Independent
Directors Committee received reports from KSK and DLJ on the events that
transpired the previous evening. At approximately 7:30 a.m., Central Time,
Bidder A increased its offer to $24.77 per share, confirmed its acceptance of
the merger agreement as proposed by CogenAmerica, and requested a two week
exclusivity period to conclude negotiation of a definitive agreement with NRG on
the terms acceptable to NRG's management subject to NRG's Board approval. A
representative of Bidder A verbally indicated to DLJ that Bidder A did not
expect to increase its offer above $24.77 per share.

     The Independent Directors Committee reconvened its meeting at approximately
7:45 a.m., Central Time, on August 13, 1999. DLJ informed the independent
directors of the August 13, 1999 letter from Bidder A and the conversation in
which Bidder A indicated that it did not expect to increase its offer. After
further discussion and considering the recommendations of DLJ and KSK, the
Independent Directors Committee authorized DLJ to contact Calpine. DLJ was
directed to inform Calpine that the Committee would accept Calpine's proposal
with the following modifications: (1) the price would be $25.00 per share, (2)
the merger agreement would be changed to provide for a one-step merger rather
than a tender offer followed by a second-step merger, and (3) any debt of
CogenAmerica that could be accelerated as a result of the merger, including the
debt owed to NRG, would be repaid upon completion of the merger.

     Calpine requested that the message be in writing and signed on behalf of
the Independent Directors Committee. Counsel for CogenAmerica then prepared a
letter dated August 13, 1999 (the "August 13 Exclusivity Letter") incorporating
the terms approved by the Independent Directors Committee. The August 13
Exclusivity Letter was signed on behalf of the Independent Directors Committee
and transmitted to Calpine via facsimile. Calpine accepted the proposal and
returned the August 13 Exclusivity Letter countersigned by Calpine. With the
consent of Calpine, DLJ advised Bidder A that Calpine had been given an
exclusive period to conclude the documentation and no further communications
would occur with Bidder A during the exclusive period.

     CogenAmerica's counsel then informed NRG of the decision by the Independent
Directors Committee and provided NRG with a copy of the August 13 Exclusivity
Letter

                                       16
<PAGE>   25

and a revised merger agreement reflecting the change in the structure to a
one-step merger from a tender offer followed by a second-step merger.

     During the morning on August 16, 1999, Calpine and its counsel met with
CogenAmerica and its counsel to finalize the merger agreement. Commencing in the
afternoon of August 16, 1999 and continuing through August 19, 1999, Calpine,
NRG and their respective counsel discussed the terms of the proposed definitive
agreement between Calpine and NRG (the "Calpine/NRG Agreement").

     On August 19, 1999, Bidder A sent by facsimile a letter addressed to the
Board of Directors of NRG, the Independent Directors Committee and the
CogenAmerica Board of Directors. The letter affirmed the interest of Bidder A to
proceed with a transaction and increased its bid to $24.99 per share. Because
CogenAmerica was bound by the exclusivity terms of the August 13 Exclusivity
Letter, no response to Bidder A's letter was made by CogenAmerica or its
officers, directors, employees, agents or representatives.

     On August 19, 1999, a Calpine representative advised CogenAmerica and NRG
that the Calpine board of directors approved the merger agreement and the
Calpine/NRG Agreement.

     On August 25, 1999, an NRG representative advised CogenAmerica and Calpine
that the NRG board of directors approved the Calpine/NRG Agreement. Meetings of
the Independent Directors Committee and Board of Directors of CogenAmerica were
called for 9:00 a.m. and 12:00 noon, respectively, on August 26, 1999.

     On August 26, 1999, commencing at approximately 9:00 a.m., Central Time,
the Independent Directors Committee held a meeting. All independent directors
were present in person as were representatives of DLJ and KSK. At the request of
the independent directors, a representative of O'Melveny & Myers ("O&M"),
counsel to the Independent Directors Committee, attended by telephone.
Representatives of KSK briefed the Independent Directors Committee regarding
their fiduciary duties and the terms of the merger agreement, the Calpine/NRG
Agreement, the agreement between CogenAmerica and NRG (the "Termination
Agreement") terminating the Affiliate Agreements upon completion of the merger,
and an agreement among CogenAmerica, Calpine and NRG (the "Cooperation
Agreement") pursuant to which the parties agree to cooperate with each other in
the preparation of this Proxy Statement and the Schedule 13E-3 that are required
to be filed with the SEC. Copies of the final agreements were available to the
independent directors and were reviewed during the meeting. Representatives of
DLJ briefed the Independent Directors Committee on the sale process and the
bases for DLJ's fairness opinion. DLJ also delivered its executed fairness
opinion addressed to the Independent Directors Committee. The independent
directors also reviewed the benefits and detriments of the proposed merger to
the unaffiliated stockholders of CogenAmerica. The factors considered by the
Independent Directors Committee are discussed below in the section called
"Reasons for the Merger." After considering these factors and the advice of its
financial and legal advisors, the Independent Directors Committee unanimously
approved the merger agreement, the charter amendment, the Calpine/NRG Agreement,
the Termination Agreement and the Cooperation Agreement, and unanimously
recommended that the CogenAmerica Board of Directors approve the merger
agreement, the charter amendment, the Calpine/NRG Agreement and the Cooperation
Agreement.

     Following conclusion of the meeting of the Independent Directors Committee
and commencing at approximately 12:00 noon, Central Time, the CogenAmerica Board
of Directors convened its meeting in Minneapolis, Minnesota to consider the
transactions contemplated by the merger agreement. All directors of CogenAmerica
were present in

                                       17
<PAGE>   26

person, except for Craig A. Mataczynski and Michael O'Sullivan who participated
by telephone. KSK briefed the CogenAmerica Board of Directors on the fiduciary
duties of the directors and the terms of the merger agreement, the Calpine/NRG
Agreement, the Termination Agreement and the Cooperation Agreement. Copies of
the agreements were available to the directors at the meeting and were reviewed
during the presentation by KSK on the agreements. Representatives of DLJ
reviewed the sale process and the bases for DLJ's fairness opinion. DLJ also
confirmed that it had delivered its executed fairness opinion to the Independent
Directors Committee and that the entire CogenAmerica Board of Directors was
entitled to rely on the opinion. The directors also reviewed the benefits and
detriments of the proposed merger to the unaffiliated stockholders of
CogenAmerica. The factors considered by the CogenAmerica Board of Directors are
discussed below in the section called "Reasons for the Merger." After
considering these factors and the advice of the financial and legal advisors to
CogenAmerica, the CogenAmerica Board of Directors unanimously approved the
merger agreement, the charter amendment, the Calpine/NRG Agreement and the
Cooperation Agreement, and unanimously recommended that the CogenAmerica
stockholders approve the merger agreement and the charter amendment.

     After the close of business on August 26, 1999, CogenAmerica executed and
delivered the merger agreement to Calpine, the Cooperation Agreement to Calpine
and NRG, and the Termination Agreement to NRG. Contemporaneously, Calpine
executed and delivered the merger agreement to CogenAmerica, the Cooperation
Agreement to CogenAmerica and NRG, and the Calpine/NRG Agreement to NRG.
Contemporaneously, NRG executed and delivered the Termination Agreement to
CogenAmerica, the Cooperation Agreement to CogenAmerica and Calpine, and the
Calpine/NRG Agreement to Calpine. Press releases announcing the transactions
contemplated by the merger agreement and Calpine/NRG Agreement were issued on
the morning of August 27, 1999.

PURPOSE, TIMING AND STRUCTURE OF THE MERGER

     The purpose for the merger is to enable Calpine to acquire 80% and NRG to
retain 20% of the entire equity interests of CogenAmerica in a transaction that
provides the public stockholders of CogenAmerica and NRG, to the extent its
equity interest in CogenAmerica is not being retained, with the opportunity to
sell all of their CogenAmerica common stock at a price which represents a
substantial premium over market prices in effect immediately prior to the
announcement of the merger.

     The timing of the execution of the merger agreement resulted from an
extensive sale process conducted by CogenAmerica after it had received four
indications of interest for the acquisition of CogenAmerica at significant
premiums to the then market price of CogenAmerica common stock. In addition, the
market for the sale of independent power company assets has recently been
favorable to sellers of such assets as significant consolidation is occurring in
the independent power industry. In addition, the Independent Directors Committee
and the Board of Directors of CogenAmerica concluded that sufficient additional
capital for CogenAmerica to make acquisitions and expand its business would be
difficult to obtain given CogenAmerica's current leverage and current stock
price and that the development of new plants, so called "green field" projects,
would be time consuming and involved significant risk that they would not be
completed after substantial management time and expense had been invested in the
projects.

     The transaction was structured to achieve both (1) the requirement by NRG
that it retain a 20% interest in CogenAmerica after completion of the merger and
(2) the

                                       18
<PAGE>   27

requirement of Calpine that it acquire the remaining 80% equity interest in
CogenAmerica in a single transaction, while at the same time facilitating a
direct cash payment at a premium price to all holders of CogenAmerica common
stock (other than shares held by CogenAmerica, by Acquisition Sub or by
stockholders who properly exercise their appraisal rights). CogenAmerica also
wished to present its stockholders with a simple transaction that treats equally
all unaffiliated stockholders.

     Acquisition Sub is currently a wholly owned subsidiary of Calpine.
Immediately prior to the completion of the merger, NRG will contribute shares of
CogenAmerica common stock to Acquisition Sub which will enable NRG to retain a
20% equity interest in CogenAmerica after completion of the merger. Calpine
formed Acquisition Sub shortly before execution of the merger agreement for the
sole purpose of carrying out the merger.

REASONS FOR THE MERGER

     The Independent Directors Committee and the Board of Directors of
CogenAmerica have determined that the merger is fair to and in the best
interests of all CogenAmerica stockholders other than NRG and unanimously
recommend that the CogenAmerica stockholders approve and adopt the merger
agreement and the charter amendment. In reaching these conclusions, the
Independent Directors Committee and the Board of Directors of CogenAmerica
considered and analyzed a number of factors. All of the material factors
considered by the CogenAmerica Board of Directors are described below.

     1. Competitive Sale Process. The merger consideration of $25.00 per share
was arrived at after an intense and competitive sale process. During the sale
process, 13 parties were contacted of which seven parties submitted preliminary
indications of interest ranging from $15.09 to $24.00 per share for 100% of the
equity interests of CogenAmerica. Six parties were invited to conduct extensive
due diligence after which firm bids were submitted. The bids ranged from $18.50
to $23.00 per share for 100% of the equity interests in CogenAmerica. The two
highest bidders, Calpine and Bidder A, were invited to conduct on-site plant
visits and to negotiate the terms of the definitive documents. Calpine and
Bidder A subsequently submitted final bids of $24.52 and $24.00, respectively.
Thereafter, Calpine raised its bid to $25.00 per share. Both the Independent
Directors Committee and the Board of Directors of CogenAmerica determined that
the manner in which the sale process was conducted was a very important factor
in concluding that the price resulting from that process was fair to the
unaffiliated stockholders.

     2. Premium over Current Market Price. On August 25, 1999, the trading day
immediately preceding the meetings of the Independent Directors Committee and
the Board of Directors of CogenAmerica, the closing sales price for CogenAmerica
common stock was $16.75 per share. The merger consideration of $25.00 per share
represented a premium of 49.3% over the closing market price on August 25, 1999.
Both the Independent Directors Committee and the Board of Directors of
CogenAmerica concluded that the significant premium over the current market
price was a very important factor in favor of the transaction and determining
the merger consideration was fair to the unaffiliated stockholders.

     3. Premium over Historical Market Price. The merger consideration of $25.00
per share represented a significant premium over the historical market price of
CogenAmerica common stock. The following premiums over historical market price
were considered to be very important factors to both the Independent Directors
Committee and the Board of

                                       19
<PAGE>   28

Directors of CogenAmerica in favor of the transaction and in their determination
that the merger consideration was fair to the unaffiliated stockholders:

<TABLE>
<CAPTION>
                                                                    PREMIUM
                                                                OVER HISTORICAL
ATE OR PERIOD TO MEASURE PREMIUM                                  MARKET PRICE
- ---------------------------------                               ---------------
<S>                                                             <C>
January 26, 1999 (the first date Bidder A met formally with
  NRG to express its interest in an acquisition
  transaction)..............................................         170.3%

May 20, 1999 (the date the CogenAmerica Board of Directors
  determined to explore strategic alternatives).............         102.0%

July 29, 1999 (four weeks prior to the approval of the
  merger agreement by the Independent Directors Committee
  and the Board of Directors of CogenAmerica)...............          40.8%

August 19, 1999 (one week prior to the approval of the
  merger agreement by the Independent Directors Committee
  and the Board of Directors of CogenAmerica)...............          50.4%
</TABLE>

In addition, both the Independent Directors Committee and the Board of Directors
of CogenAmerica considered very important the fact that the historical daily
trading volume of CogenAmerica common stock was relatively small, it being in
the range of 12,000 to 13,000 shares or approximately 0.2% of the outstanding
shares. The merger would enable all unaffiliated stockholders to sell their
shares for cash without any depressing effect that the sale of a considerable
number of shares might have on the market price of the CogenAmerica common
stock.

     4. Presentation and Opinion of DLJ. Both the Independent Directors
Committee and the Board of Directors of CogenAmerica considered very important
the presentation made by DLJ at their meetings on August 26, 1999 and DLJ's
fairness opinion addressed to the Independent Directors Committee in determining
that the merger was fair to the unaffiliated stockholders. For a discussion of
the DLJ presentation, see the caption entitled "Opinion of Financial Advisor"
below and see Appendix C for a copy of the full text of the written opinion of
DLJ dated August 26, 1999 which sets forth assumptions made, matters considered
and limitations on the review undertaken in connection with the opinion.

     5. Going Concern Value. As part of its presentation to the Independent
Directors Committee and the Board of Directors of CogenAmerica on August 26,
1999, DLJ presented a discounted cash flow analysis of the value of CogenAmerica
as a going concern. Depending on the assumptions for discount rate and multiple
of earnings before interest, taxes, depreciation and amortization for the
terminal value, the discounted cash flow analysis indicated an implied value of
CogenAmerica common stock in the range of $9.62 per share to $22.39 per share.
Although the Independent Directors Committee and the Board of Directors of
CogenAmerica considered the going concern value (as expressed by the discounted
cash flow analysis by DLJ) as an important factor supporting the fairness of the
merger consideration to the unaffiliated stockholders, this factor was somewhat
less important than the other four factors discussed above.

     6. Future Prospects as a Public Company. Both the Independent Directors
Committee and the Board of Directors of CogenAmerica considered the future
prospects of CogenAmerica as an independent public company. In order for
CogenAmerica to continue its growth, CogenAmerica had to acquire or develop
additional independent

                                       20
<PAGE>   29

power plants. CogenAmerica would require additional capital to provide the
financial resources necessary for the acquisition or development of new
projects. Due to the current high leverage of CogenAmerica, additional debt
might not be available or, if available, would be at high interest rates. An
analysis by management indicated that the sale of CogenAmerica common stock at a
price below $20.00 per share would be dilutive of future earnings and,
therefore, not a viable alternative to raising capital. Also, due to the low
earnings multiple for CogenAmerica and the competitive prices for independent
power plants, it would be difficult for CogenAmerica to make acquisitions using
its stock that would be accretive to future earnings. The current competitive
market for existing independent power plants made acquisitions of existing
plants expensive. The development of new plants, so-called "green field"
projects, required a substantial amount of time and investment without any
assurance that CogenAmerica would be awarded the project. Based on
CogenAmerica's capital constraints and risks of future expansion, both the
Independent Directors Committee and the Board of Directors of CogenAmerica
considered this factor to be important in determining that the merger was the
best alternative for the unaffiliated stockholders.

     7. Right to Terminate Merger Agreement. After following certain procedures
and paying Calpine a termination fee of $7,500,000, CogenAmerica has the right
to terminate the merger agreement in order to accept a superior takeover
proposal from a third party. This so-called "fiduciary out" provision is
described in "Summary of Material Features of the Merger -- Termination" below.
The Calpine/NRG Agreement provides that the agreement terminates in the event
the merger agreement terminates. As a result, if CogenAmerica received a
superior takeover proposal from a third party, it would be able to terminate the
merger agreement by following the requisite procedures, and NRG would be able to
enter into an agreement with the third party on terms comparable to the Calpine/
NRG Agreement. This would enable the Independent Directors Committee and the
Board of Directors of CogenAmerica to accept a takeover proposal that provides
more value to the unaffiliated stockholders of CogenAmerica. Both the
Independent Directors Committee and the Board of Directors of CogenAmerica
considered the fiduciary out provision of the merger agreement a significant
factor in determining the merger was fair to the unaffiliated stockholders.

     8. Financial Ability of Calpine. Calpine has the financial ability to
complete the merger and support CogenAmerica's future business operations. The
merger agreement is not conditioned on financing by Calpine. Both the
Independent Directors Committee and the Board of Directors of CogenAmerica
considered the financial ability of Calpine to fund the merger consideration to
be a significant factor in approving the merger agreement.

     9. Appraisal Rights. Stockholders of CogenAmerica who do not support the
merger or are dissatisfied with the consideration to be received by the holders
of CogenAmerica common stock are able to obtain "fair value" for their shares if
they properly exercise their appraisal rights under the DGCL. Both the
Independent Directors Committee and the Board of Directors of CogenAmerica
considered the ability of unaffiliated stockholders to exercise their appraisal
rights as a favorable factor, but not as important as the factors enumerated
above in paragraphs 1 through 8.

     10. Stockholder Vote. Pursuant to the Calpine/NRG Agreement, NRG has
granted its proxy to Calpine to vote the CogenAmerica shares held by NRG for
approval and adoption of the merger agreement and the charter amendment. Based
on the fact that Calpine would not proceed with the transaction unless NRG
agreed to grant its proxy to Calpine to vote NRG's CogenAmerica shares in favor
of the merger agreement and the

                                       21
<PAGE>   30

charter amendment at the special meeting and that, as discussed in paragraph 7
above, the Calpine/NRG Agreement would terminate in the event the CogenAmerica
Board of Directors exercised its "fiduciary out" to terminate the merger
agreement in order to accept a superior takeover proposal from another party,
the Independent Directors Committee and the Board of Directors of CogenAmerica
did not consider the lack of a vote of the majority of the minority as an
important factor.

     11. Net Book Value. The Independent Directors Committee and the Board of
Directors of CogenAmerica did not consider the net book value of CogenAmerica as
a relevant factor in its determination.

     12. Liquidation Value. Neither the Independent Directors Committee nor the
Board of Directors of CogenAmerica considered the liquidation value of
CogenAmerica as a relevant factor in its determination. A liquidation of the
assets would result in CogenAmerica paying taxes on the gain from the sale of
its assets. Therefore, the net proceeds from the sale of its assets would be
reduced by taxes and transaction costs before any distribution could be made to
stockholders.

     13. Price Paid by NRG for CogenAmerica Common Stock. NRG facilitated the
reorganization of CogenAmerica's predecessor in 1996 under Chapter 11 of the
Federal Bankruptcy Laws by contributing an aggregate of $21.2 million to the
predecessor in exchange for 2,710,357 shares of the predecessor's common stock
representing approximately 41.86% of the outstanding shares of CogenAmerica
common stock after giving effect to such issuance. The price per share of
CogenAmerica common stock paid by NRG was $3.27. Since the operations of
CogenAmerica have substantially improved since that time, including the addition
of two plants after the 1996 reorganization, neither the Independent Directors
Committee nor the Board of Directors of CogenAmerica considered the price paid
by NRG for its shares of CogenAmerica common stock as a relevant factor in its
determination.

     In view of the variety of factors considered in connection with its
evaluation of the merger, the Independent Directors Committee and the Board of
Directors of CogenAmerica found it impracticable to, and did not, quantify, rank
or otherwise assign relative weights to the reasons for the merger described
above or determine that any reason was of particular importance in reaching its
determination that the merger is fair to and in the best interest of
CogenAmerica stockholders (other than NRG), except that the factors enumerated
in paragraphs 1 through 4 above were the most important, the factors enumerated
in paragraphs 5 and 6 above were important, the factors in paragraphs 7 and 8
were also important but less significant than the first six factors, the factor
enumerated in paragraph 9 was less significant than the first eight factors, the
factor enumerated in paragraph 10 was not important, and the factors enumerated
in paragraphs 11 through 13 were not relevant. The Independent Directors
Committee and the Board of Directors of CogenAmerica view their recommendations
as being based upon their judgment, in light of the totality of the information
presented and considered, as summarized in the reasons for the merger described
above, and the overall effect of the merger on CogenAmerica's stockholders
compared to continuing the business of CogenAmerica in the ordinary course or
seeking other potential parties to effect a business combination.

                                       22
<PAGE>   31

RECOMMENDATIONS OF THE INDEPENDENT DIRECTORS COMMITTEE AND THE BOARD OF
DIRECTORS

     The Independent Directors Committee is a standing committee of the
CogenAmerica Board of Directors that is comprised of three disinterested
directors. The purpose of the Independent Directors Committee is to consider and
act upon matters where the interests of NRG, as the principal stockholder and
whose officers constitute four members of the CogenAmerica Board of Directors,
may be in conflict with the interests of the unaffiliated stockholders of
CogenAmerica. When it became apparent in the sale process undertaken by
CogenAmerica that NRG would be treated differently from the unaffiliated
stockholders of CogenAmerica, the Independent Directors Committee took over
control of the sale process. The Independent Directors Committee then retained
financial and legal advisors to assist it in the sale process and the other
matters related to the transactions contemplated by the merger agreement. On
August 26, 1999, the Independent Directors Committee determined that the merger
was in the best interests of CogenAmerica and was fair to CogenAmerica
stockholders (other than NRG). Accordingly, the Independent Directors Committee
unanimously approved the merger agreement, the charter amendment, the
Termination Agreement, the Calpine/NRG Agreement and the Cooperation Agreement,
and recommended that the CogenAmerica Board of Directors approve the merger
agreement, the charter amendment and the Cooperation Agreement after receiving
reports from its financial and legal advisors, including reports on the sale
process, the terms of the operative documents and the valuation analysis by DLJ,
and the written opinion from DLJ that, as of its date and subject to the
assumptions, limitations and qualifications set forth in the written opinion,
the consideration to be paid to the CogenAmerica stockholders (other than NRG)
in the merger was fair from a financial point of view. The Independent Directors
Committee took such actions for the reasons set forth above under the caption
"Reasons for the Merger."

     Following the meeting of the Independent Directors Committee, the
CogenAmerica Board of Directors held a meeting on August 26, 1999 to consider
the transactions contemplated by the merger agreement. The CogenAmerica Board of
Directors received reports from financial and legal advisors for CogenAmerica.
The reports included a review of the sale process, a discussion of the terms of
the operative agreements and the valuation analysis by DLJ. DLJ also provided
the directors with a copy of the opinion of DLJ addressed to the Independent
Directors Committee that, as of its date and subject to the assumptions,
limitations and qualifications set forth in the written opinion, the
consideration to be paid to the stockholders other than NRG in the merger was
fair from a financial point of view, and DLJ indicated that the directors were
entitled to rely on the opinion. The Independent Directors Committee also
informed the CogenAmerica Board of Directors that it had unanimously approved
the merger agreement, the charter amendment, the Termination Agreement, the
Calpine/NRG Agreement and the Cooperation Agreement, and unanimously recommended
that the CogenAmerica Board of Directors approve the merger agreement, the
charter amendment and the Cooperation Agreement. Based on these reports and
recommendations and for the reasons set forth above under the caption "Reasons
for the Merger," the CogenAmerica Board of Directors also determined that the
merger was in the best interests of CogenAmerica and was fair to the
unaffiliated stockholders of CogenAmerica. The CogenAmerica Board of Directors
unanimously approved the merger agreement, the charter amendment, the
Calpine/NRG Agreement and the Cooperation Agreement and recommended that the
CogenAmerica stockholders approve the merger agreement and the charter
amendment.

                                       23
<PAGE>   32

     THE INDEPENDENT DIRECTORS COMMITTEE AND THE BOARD OF DIRECTORS OF
COGENAMERICA HAVE UNANIMOUSLY APPROVED THE MERGER AGREEMENT AND THE CHARTER
AMENDMENT, AND THE COGENAMERICA BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT
THE COGENAMERICA STOCKHOLDERS VOTE FOR APPROVAL AND ADOPTION OF THE MERGER
AGREEMENT AND THE CHARTER AMENDMENT.

OPINION OF FINANCIAL ADVISOR

     CogenAmerica asked DLJ, in its role as financial advisor to CogenAmerica,
to render an opinion to the Independent Directors Committee of CogenAmerica as
to the fairness, from a financial point of view, to the holders of CogenAmerica
common stock, other than NRG, of the consideration to be received by such
holders in the merger. On August 26, 1999, DLJ delivered to the Independent
Directors Committee its written opinion to the effect that, as of such date,
based on and subject to the assumptions, limitations and qualifications set
forth in such written opinion, the consideration to be received in the merger by
the holders of CogenAmerica common stock, other than NRG, was fair to such
holders from a financial point of view.

     THE FULL TEXT OF DLJ'S OPINION IS ATTACHED AS APPENDIX C TO THIS PROXY
STATEMENT. THE SUMMARY OF DLJ'S OPINION SET FORTH IN THIS PROXY STATEMENT IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO THE FULL TEXT OF DLJ'S OPINION.
COGENAMERICA STOCKHOLDERS ARE URGED TO READ DLJ'S OPINION CAREFULLY AND IN ITS
ENTIRETY FOR THE PROCEDURES FOLLOWED, ASSUMPTIONS MADE, OTHER MATTERS CONSIDERED
AND LIMITS OF THE REVIEW BY DLJ IN CONNECTION WITH SUCH OPINION.

     DLJ PREPARED ITS OPINION FOR THE INDEPENDENT DIRECTORS COMMITTEE SOLELY
WITH RESPECT TO THE FAIRNESS FROM A FINANCIAL POINT OF VIEW OF THE CONSIDERATION
TO BE RECEIVED IN THE MERGER BY HOLDERS OF COGENAMERICA COMMON STOCK, OTHER THAN
NRG, AS OF THE DATE THEREOF. DLJ EXPRESSED NO OPINION AS TO THE PRICES AT WHICH
COGENAMERICA COMMON STOCK WOULD ACTUALLY TRADE AT ANY TIME AND DOES NOT ADDRESS
THE RELATIVE MERITS OF THE MERGER AND THE OTHER BUSINESS STRATEGIES CONSIDERED
BY THE INDEPENDENT DIRECTORS COMMITTEE NOR DOES IT ADDRESS THE INDEPENDENT
DIRECTORS COMMITTEE'S DECISION TO PROCEED WITH THE MERGER. DLJ'S OPINION DOES
NOT ADDRESS ANY OTHER ASPECT OF THE MERGER NOR DOES IT CONSTITUTE A
RECOMMENDATION TO ANY COGENAMERICA STOCKHOLDER AS TO HOW TO VOTE ON THE MERGER
AND SHOULD NOT BE RELIED UPON BY ANY STOCKHOLDER AS SUCH.

     CogenAmerica selected DLJ as its financial advisor because DLJ is an
internationally recognized investment banking firm that has substantial
experience providing strategic advisory services. DLJ was not retained as an
advisor or agent to the stockholders of CogenAmerica or any other person. As
part of its investment banking business, DLJ is regularly engaged in the
valuation of businesses and securities in connection with mergers, acquisitions,
underwritings, sales and distributions of listed and unlisted securities,
private placements and valuations for corporate and other purposes. CogenAmerica
did not impose any restrictions or limitations upon DLJ with respect to the
investigations made or the procedures followed by DLJ in rendering its opinion.
For purposes of rendering its opinion, DLJ among other things, reviewed the
Agreement and Plan of Merger and the company letter, dated August 26, 1999, and
the Calpine/NRG Agreement, also dated August 26, 1999, which sets forth the
essential terms and conditions upon which NRG would be able to sell its
CogenAmerica common stock. DLJ also reviewed certain financial and other
business information that was publicly available or furnished by CogenAmerica,
including information provided during discussions with management, for recent
years and interim

                                       24
<PAGE>   33

periods to date. Included in the information provided during discussions with
management were certain internal financial forecasts and projections of the
Company for the period beginning January 1, 1999 and ending December 31, 2009
prepared by the management of the Company. DLJ met with the management of
CogenAmerica to review and discuss such information and the Company's business,
operations, assets, financial condition and future prospects.

     In addition, DLJ reviewed the historical stock prices and trading volumes
of CogenAmerica common stock, reviewed prices and premiums paid in certain other
business combinations and conducted such other financial studies, analyses and
investigations as DLJ deemed appropriate for purposes of rendering its opinion.

     In rendering its opinion, DLJ assumed and relied upon without independent
verification the accuracy and completeness of all of the financial and other
information that was available to it from public sources, that was provided to
it by CogenAmerica, or its representatives, or that was otherwise reviewed by
DLJ. With respect to the financial projections and assumptions supplied to DLJ,
DLJ assumed that they were reasonably prepared on bases reflecting the best
currently available estimates and judgments of the management of CogenAmerica as
to the future operating and financial performance of CogenAmerica. DLJ expressed
no opinion with respect to such projections, forecasts and analyses or the
assumptions upon which they were based. DLJ did not make any independent
valuation or appraisal of the assets or liabilities of CogenAmerica and did not
make any independent verification of the information reviewed by DLJ. DLJ was
not furnished with any such valuations or appraisals. DLJ's opinion was
necessarily based on economic, market, financial and other conditions as they
existed on, and on the information made available to DLJ as of, the date of its
opinion. DLJ states in its opinion that, although subsequent developments may
affect its opinion, DLJ does not have any obligation to update, revise or
reaffirm its opinion.

     The following is a summary of the financial analyses presented by DLJ to
the Independent Directors Committee on August 26, 1999 in connection with the
preparation of DLJ's opinion.

     Common Stock Trading History. DLJ examined the historical closing prices of
CogenAmerica common stock from August 20, 1998 to August 23, 1999. During this
time period, CogenAmerica common stock reached a high of $18.13 per share and a
low of $7.94 per share. DLJ also examined the historical trading range of
CogenAmerica common stock from August 20, 1998 to August 23, 1999 relative to an
independent power producer index made up of The AES Corporation, Calpine
Corporation, MidAmerican Energy Holdings Company, Trigen Energy Corporation and
CogenAmerica. This information was presented solely to provide the Independent
Directors Committee with background information on the stock price of
CogenAmerica over the periods indicated.

     Premiums Paid Analysis. DLJ determined the premium over the common stock
trading prices for one day, one week and four weeks prior to the announcement
date in all merger and acquisition transactions of U.S. public companies ranging
from $250 million to $750 million in size announced between January 1, 1996 and
August 20, 1999. DLJ obtained information for this analysis from Securities Data
Corp. DLJ analyzed the high, low and median of the premiums paid one day, one
week and four weeks prior to the announcement date. The median premiums for the
selected transactions over the common stock trading prices for one day, one week
and four weeks prior to the announcement date were 23.3%, 29.3% and 36.7%,
respectively. Applying the median premiums to the closing

                                       25
<PAGE>   34

price of CogenAmerica one day, one week and four weeks prior to the announcement
date, DLJ estimated a value per share of CogenAmerica common stock ranging from
$21.42 to $24.61.

     Comparable Publicly Traded Company Analysis. As part of its analysis, DLJ
compared the market values and trading multiples of CogenAmerica with that of
the following publicly traded independent power companies:

     1. The AES Corporation

     2. Calpine Corporation

     3. MidAmerican Energy Holdings Company (formerly CalEnergy Company, Inc.),
and

     4. Trigen Energy Corporation.

In examining these comparable companies, DLJ calculated the enterprise value of
each company as a multiple of its respective: LTM revenue; LTM EBITDA and LTM
EBIT. LTM means last reported twelve months. EBITDA means earnings before
interest expense, income taxes, depreciation and amortization. EBIT means
earnings before interest expense and income taxes. DLJ also calculated the
equity value of each company as a multiple of its respective: LTM net income;
and projected net income for the calendar year 1999. The enterprise value of a
company is equal to the value of its fully-diluted common equity plus debt and
the liquidation value of outstanding preferred stock, if any, minus cash and the
value of certain other assets, including minority interests in other entities.
Projected net income for the calendar year 1999 was obtained from First Call
estimates. For the purpose of this analysis, DLJ calculated EBITDA and EBIT to
include equity in income/loss of affiliates, and calculated enterprise value to
include investment in unconsolidated affiliates.

     DLJ's analysis of the comparable companies yielded the following: revenue
multiples for the LTM ended June 30, 1999 ranging from 1.8x to 8.3x; EBITDA
multiples for the LTM ended June 30, 1999 ranging from 7.9x to 16.7x; EBIT
multiples for the LTM ended June 30, 1999 ranging from 14.1x to 24.8x; net
income multiples for the LTM ended June 30, 1999 ranging from 9.7x to 41.6x; and
projected net income multiples for the calendar year 1999 ranging from 14.0x to
34.0x. Based on an analysis of this data and CogenAmerica's results for
comparable periods, DLJ estimated a value per share of CogenAmerica common stock
ranging from $16.10 to $34.40.

     No company utilized in the comparable public company analysis is identical
to CogenAmerica. Accordingly, an analysis of the results of the foregoing
necessarily involves complex considerations and judgements concerning
differences in financial and operating characteristics of CogenAmerica and other
factors that could affect the public trading value of the companies to which it
is being compared. In evaluating the comparable companies, DLJ made judgments
and assumptions with regard to industry performance, general business, economic,
market and financial conditions and other matters, many of which are beyond the
control of CogenAmerica, such as the impact of competition on CogenAmerica and
the industry generally, industry growth and the assumed absence of any adverse
material change in the financial conditions and prospects of CogenAmerica or the
industry or in the financial markets in general. Mathematical analysis (such as
determining the mean or median) is not, in itself, a meaningful method of using
comparable company data.

                                       26
<PAGE>   35

     Precedent Merger and Acquisition Transaction Analysis. DLJ analyzed
acquisition multiples paid in the acquisition of Sithe Energies by Marubeni
Corporation. This was the most comparable acquisition of a publicly traded
independent power company occurring prior to August 26, 1999. DLJ's analysis of
this comparable transaction yielded the following: (i) a revenue multiple for
the LTM ended September 30, 1995 of 3.3x; (ii) an EBITDA multiple for the LTM
ended September 30, 1995 of 10.4x; (iii) an EBIT multiple for the LTM ended
September 30, 1995 of 13.7x; and (iv) a net income multiple for the LTM ended
September 30, 1995 of 29.2x. Based on an analysis of this data and
CogenAmerica's results for comparable periods, DLJ estimated a value per share
of CogenAmerica common stock ranging from $20.81 to $32.80.

     Using publicly available information, DLJ also reviewed certain
acquisitions involving the sale of generation assets by various independent
power companies and public utilities conducted over the year to date period
beginning January 1, 1999. In examining these transactions, DLJ analyzed the
enterprise value of the acquired assets as a multiple of their net generating
capacity. DLJ applied the high, low, median and average of these multiples to
CogenAmerica's net generating capacity to obtain an enterprise value, and equity
value per share. DLJ's analysis yielded an enterprise value multiple range of
$147/kW to $955/kW. Based on an analysis of this data and CogenAmerica's net
generating capacity, DLJ estimated a valuation range of CogenAmerica common
stock with a high end of $27.78 per share. The other end of the range was deemed
not meaningful due to CogenAmerica's relatively high enterprise value to net
generating capacity compared to the sample transactions that were examined by
DLJ. No transaction utilized as a comparison in the analysis of selected
precedent transactions is identical to the merger in both timing and size.
Accordingly, an analysis of the results of the foregoing necessarily involves
complex considerations and judgments concerning differences in financial and
operating characteristics of CogenAmerica and other factors that would affect
the acquisition value of the companies to which it is being compared. In
evaluating the precedent transactions, DLJ made judgments and assumptions with
regard to industry performance, global business, economic, market and financial
conditions and other matters, many of which are beyond the control of
CogenAmerica, such as the impact of competition on CogenAmerica and the industry
generally, industry growth and the assumed absence of any adverse material
change in the financial conditions and prospects of CogenAmerica or the industry
or the financial markets in general. Mathematical analysis (such as determining
the mean or median) is not, in itself, a meaningful method of using precedent
transactions data.

     Discounted Cash Flow ("DCF") Analysis. DLJ also performed a DCF analysis of
the projected cash flows of CogenAmerica for the fiscal years ending December
31, 2000 through December 31, 2009, using projections and growth assumptions
provided by the management of CogenAmerica. The DCFs for CogenAmerica were
estimated using discount rates ranging from 9% to 11%, based on estimates of and
judgments related to the weighted average costs of capital of CogenAmerica, and
terminal multiples of estimated EBITDA for CogenAmerica's fiscal year ending
December 31, 2009 ranging from 9.0x to 12.0x. Based on this analysis, DLJ
estimated a value per share of CogenAmerica common stock ranging from $9.62 to
$22.39.

     The summary set forth above does not purport to be a complete description
of the analyses performed by DLJ but describes, in summary form, the material
elements of the presentation made by DLJ to the Independent Directors Committee
on August 26, 1999. The preparation of a fairness opinion involves various
determinations as to the most appropriate and relevant methods of financial
analysis and the application of these methods

                                       27
<PAGE>   36

to the particular circumstances and, therefore, such an opinion is not readily
susceptible to partial analysis or summary description. Each of the analyses
conducted by DLJ was carried out in order to provide a different perspective on
the transaction and to add to the total mix of information available. DLJ did
not form a conclusion as to whether any individual analysis, considered in
isolation, supported or failed to support an opinion as to fairness from a
financial point of view. Rather, in reaching its conclusion, DLJ considered the
results of the analyses in light of each other and ultimately reached its
opinion based on the results of all analyses taken as a whole. DLJ did not place
any particular reliance or weight on any individual analysis or factor
considered by it, but instead concluded that its analyses, taken as a whole,
supported its determination. Accordingly, notwithstanding the separate factors
summarized above, DLJ has indicated to CogenAmerica that it believes that its
analyses must be considered as a whole and that selecting portions of its
analyses and the factors considered by it, without considering all analyses and
factors, could create an incomplete view of the evaluation process underlying
its opinion. The analyses performed by DLJ are not necessarily indicative of
actual values or future results, which may be significantly more or less
favorable than suggested by such analyses. Such analyses were prepared solely as
part of DLJ's analysis of the fairness of the merger price, pursuant to the
merger agreement, from a financial point of view to the holders of shares of
CogenAmerica common stock, other than NRG, and were provided to the CogenAmerica
Board of Directors in connection with the delivery of DLJ's written opinion,
dated August 26, 1999. The analyses do not purport to be appraisals or to
reflect the prices at which CogenAmerica might actually be sold. In addition, as
described above, DLJ's opinion and presentation to the CogenAmerica Board of
Directors is one of many factors taken into consideration by the CogenAmerica
Board of Directors in making its determination to approve the merger.
Consequently, the DLJ analysis described above should not be viewed as
determinative of the opinion of the CogenAmerica Board of Directors or the view
of the management of CogenAmerica with respect to the value of CogenAmerica.

     Other Relationships. In the ordinary course of business, DLJ and its
affiliates may own or actively trade the securities of CogenAmerica, Calpine and
NSP for their own accounts and for the accounts of their customers and,
accordingly, may at any time hold a long or short position in CogenAmerica, NSP
or Calpine securities. In addition, DLJ, as part of its investment banking
services, is regularly engaged in the valuation of businesses and securities in
connection with mergers, acquisitions, underwritings, sales and distributions of
listed and unlisted securities, private placements and valuations for estate,
corporate and other purposes. DLJ has performed investment banking services for
CogenAmerica and Calpine in the past and has been compensated for such services.

     Engagement Letter. Pursuant to the terms of a letter agreement, dated June
3, 1999, between CogenAmerica and DLJ, CogenAmerica (1) has agreed to pay DLJ
(a) a retainer fee of $200,000 and (b) a fee of $750,000 upon notification by
DLJ that it is prepared to deliver a fairness opinion with respect to a
transaction covered under the letter agreement, and (2) a transaction fee equal
to $2,500,000; plus, if the price per share of the outstanding CogenAmerica
common stock in any transaction exceeds $21.00, three percent (3%) of the amount
by which such price per share exceeds $21.00 multiplied by the number of shares
of CogenAmerica common stock outstanding (treating any shares issuable upon
exercise of options, warrants or other rights of conversion as outstanding) upon
consummation of the merger. The fees paid to DLJ pursuant to clause (1) of the
first sentence of this paragraph are to be deducted from the transaction fee to
which DLJ is entitled upon consummation of the merger. In addition, CogenAmerica
has agreed to

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<PAGE>   37

reimburse DLJ, upon request by DLJ from time to time, for all out-of-pocket
expenses (including the reasonable fees and expenses of counsel) incurred by DLJ
in connection with its engagement and to indemnify DLJ and certain related
persons against certain liabilities and expenses in connection with its
engagement, including liabilities under federal securities laws. DLJ and
CogenAmerica negotiated the terms of the fee arrangement.

PERSPECTIVE OF NRG ON THE FAIRNESS OF THE MERGER

     NRG made no independent evaluation or determination of the substantive
fairness of the merger to the unaffiliated CogenAmerica stockholders. The
Independent Directors Committee and DLJ made a determination as to the
substantive fairness of the transaction. See "Special Factors - Recommendations
of the Independent Directors Committee and the Board of Directors" and
"-- Opinion of Financial Advisor." NRG believes that the merger is procedurally
fair to the holders of the non-affiliated stock for the following reasons:

          1. The Independent Directors Committee consisted only of board members
     representing solely the interests of CogenAmerica and the stockholders
     other than NRG.

          2. The Independent Directors Committee was advised by independent
     legal counsel retained to negotiate on behalf of CogenAmerica and the
     stockholders other than NRG.

          3. The Independent Directors Committee retained, and received advice
     from, DLJ as its independent financial advisor to assist in the conduct of
     a sale process and assist in the evaluation of the proposed transaction.

          4. The $25.00 per share price and the other terms and conditions of
     the merger agreement resulted from an extensive sale process and
     arms'-length bargaining between representatives of the Independent
     Directors Committee and Calpine and their respective advisors.

PLANS FOR COGENAMERICA AFTER THE MERGER

     Calpine intends to conduct a review of CogenAmerica and its assets,
corporate structure, dividend policy, capitalization, operations, properties and
policies and to consider, subject to the terms of the merger agreement, what, if
any, changes would be desirable in light of the circumstances then existing, and
reserves the right to take such actions or effect such changes as it deems
desirable. Such changes could include changes in CogenAmerica's business,
operations, corporate structure, capitalization, Board of Directors, or
policies.

     Upon consummation of the merger, Calpine will own 80% of the fully-diluted
equity and voting power of CogenAmerica. The merger agreement provides that the
directors and officers of Acquisition Sub will be the directors and officers of
CogenAmerica after the completion of the merger. The Calpine/NRG Agreement
provides that the board of directors of the surviving corporation will consist
of no more than seven directors, one of which shall be appointed by NRG.

     Except as described in this proxy statement, Calpine and its affiliates
currently have no plans or proposals which relate to or would result in an
extraordinary corporate transaction involving CogenAmerica or any of its
subsidiaries, such as a merger,

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<PAGE>   38

reorganization, liquidation, relocation of any operations or sale or other
transfer of a material amount of assets, any change in the CogenAmerica Board of
Directors or management (other than as described above), any material change in
CogenAmerica's capitalization or dividend policy or any other material change in
CogenAmerica's corporate structure or business, CogenAmerica Board of Directors
or management.

CERTAIN EFFECTS OF THE MERGER

     As a result of the merger, the equity interests of CogenAmerica will be
owned 80% by Calpine and 20% by NRG, and the current stockholders, other than
NRG, will have no continuing interest in CogenAmerica. Therefore, following the
merger, the stockholders of CogenAmerica, other than NRG, will no longer benefit
from any increases in the value of CogenAmerica and will no longer bear the risk
of any decreases in the value of CogenAmerica. Following the merger, the
operation of CogenAmerica will be subject, among other things, to the agreements
between Calpine and NRG reflected in the Calpine/NRG Agreement. For a
description of the Calpine/NRG Agreement, see the section under the caption
"Summary of Calpine/NRG Agreement" below.

     Following the merger, the CogenAmerica common stock will no longer meet the
requirements of The Nasdaq National Market for continued listing and therefore
will be delisted from The Nasdaq National Market.

     CogenAmerica common stock is currently registered as a class of securities
under the Securities Exchange Act of 1934, as amended (the "Exchange Act").
Registration of the CogenAmerica common stock under the Exchange Act may be
terminated upon application of CogenAmerica to the SEC if the CogenAmerica
common stock is not listed on a national securities exchange or quoted on the
Nasdaq National Market and there are fewer than 300 record holders of the
CogenAmerica common stock. Termination of registration of the CogenAmerica
common stock under the Exchange Act would substantially reduce the information
required to be furnished by CogenAmerica to its stockholders and to the SEC and
would make certain provisions of the Exchange Act, such as the short-swing
trading provisions of Section 16(b), the requirement of furnishing a proxy
statement in connection with the stockholders' meetings pursuant to Section
14(a), and the requirements of Rule 13e-3 under the Exchange Act with respect to
"going private" transactions, no longer applicable to CogenAmerica. It is the
present intention of Calpine and NRG to cause CogenAmerica to make an
application for the termination of the registration of the CogenAmerica common
stock under the Exchange Act as soon as practicable after completion of the
merger.

UNSOLICITED OFFERS FROM THIRD PARTIES

     Since entering into the merger agreement on August 26, 1999 to the date of
this proxy statement, CogenAmerica has not received any unsolicited offers from
third parties for a merger or other business combination involving CogenAmerica
or any of its subsidiaries or any unsolicited proposal or offer to acquire in
any manner a substantial equity interest in, a substantial portion of the voting
securities of, or a substantial portion of the assets of CogenAmerica or any of
its subsidiaries, other than the transactions contemplated by the merger
agreement.

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<PAGE>   39

CONFLICTS OF INTEREST

     In considering the actions of the Independent Directors Committee and the
Board of Directors of CogenAmerica with respect to the merger, stockholders
should be aware that directors and officers of CogenAmerica, as well as NRG,
have interests in connection with the merger which may present them with actual
or potential conflicts of interest as summarized below. The CogenAmerica Board
of Directors was aware of these interests and considered them among the other
matters described, but such conflicts,individually or in the aggregate, did not
influence the determination of the Independent Directors Committee or the Board
of Directors of CogenAmerica that the merger is fair to and in the best
interests of the CogenAmerica stockholders (other than NRG).

     Arrangements with NRG. As of the close of business on August 26, 1999, the
date on which the merger agreement was signed, NRG beneficially owned 3,106,612
shares of CogenAmerica common stock, or approximately 45.3% of the outstanding
shares of CogenAmerica common stock. NRG and its subsidiaries also have various
agreements with CogenAmerica and its subsidiaries that affect the operation and
conduct of CogenAmerica's business. The agreements consist of the following: (1)
a co-investment agreement pursuant to which NRG agreed to offer to sell
CogenAmerica certain independent power plants which is how CogenAmerica acquired
the power plants it currently owns in Pryor, Oklahoma and Morris, Illinois; (2)
a management services agreement pursuant to which NRG provides certain
management and technical services to CogenAmerica and its subsidiaries and is
reimbursed for its costs and expenses for providing the services; (3) separate
operation and maintenance agreements (each an "O&M Agreement") for
CogenAmerica's plants in Newark and Parlin, New Jersey and Morris, Illinois
pursuant to which NRG operates those plants in return for a fixed annual fee
subject to certain offsets plus reimbursement of all costs and expenses incurred
to operate the plants; (4) loan and security agreements pursuant to which NRG
made certain loans to CogenAmerica or its subsidiaries and was granted certain
security interests in the assets of CogenAmerica or its subsidiaries; and (5)
various agreements pursuant to which either NRG or CogenAmerica sold the other
certain assets or stock of certain corporations. Pursuant to the co-investment
agreement, NRG sold CogenAmerica the plant in Pryor, Oklahoma for $23.9 million
in 1998 and the plant in Morris, Illinois for a development fee of $4.8 million
paid to NRG plus assumption of liabilities related to the project. For the year
ended December 31, 1998 and the six months ended June 30, 1999, NRG has charged
CogenAmerica $422,227 and $52,527, respectively, under the management services
agreement. For the year ended December 31, 1998 and the six months ended June
30, 1999, NRG has charged CogenAmerica management fees of $147,033 and $73,641,
respectively, and operating cost reimbursements of $35,657 and $17,904,
respectively, under the O&M Agreement for the Newark, New Jersey plant. For the
year ended December 31, 1998 and the six months ended June 30, 1999, NRG has
charged CogenAmerica management fees of $196,044 and $98,189, respectively, and
operating cost reimbursements of $59,705 and $24,180, respectively, under the
O&M Agreement for the Parlin, New Jersey plant. For the year ended December 31,
1998 and the six months ended June 30, 1999, NRG has charged CogenAmerica
management fees of none and $166,667, respectively, and operating cost
reimbursements of none and $35,883, respectively, under the O&M Agreement for
the Morris, Illinois plant. As of August 31, 1999, CogenAmerica owed NRG for
borrowed money an aggregate of $55,191,100 consisting of $53,933,649 in
principal and $1,257,451 in accrued interest. In connection with completion of
the merger, the various Affiliate Agreements will be terminated

                                       31
<PAGE>   40

pursuant to the Termination Agreement and the NRG and CogenAmerica parties will
exchange mutual general releases subject to certain exceptions.

     Arrangements between Calpine and NRG. In addition to the Calpine/NRG
Agreement, Calpine and NRG entered into an acknowledgement pursuant to which NRG
consented to the execution of certain agreements by CogenAmerica at the
effective time of the merger with Calpine including (i) a tax sharing agreement,
(ii) a management services agreement, (iii) operating and maintenance agreements
for certain of CogenAmerica's project subsidiaries and (iv) a form of energy
services agreement which may be entered into with certain of CogenAmerica's
project subsidiaries.

     The tax sharing agreement, which will be entered into at the effective time
of the merger, allocates responsibility between Calpine and CogenAmerica for
preparing and filing tax returns and specifies which party will make tax
payments and how tax liabilities and obligations will be allocated among the
parties.

     The form of energy services agreement, if entered into between Calpine and
a CogenAmerica project subsidiary, provides that Calpine will provide fuel
management, marketing and contract administration services in connection with
such subsidiary's gas agreements and will perform certain other services related
to the project. The agreement also provides that Calpine will provide marketing,
scheduling and contract administration services with respect to power generated
by each such project. Under the agreement, in exchange for such services,
CogenAmerica will pay Calpine $10,000 per month in the aggregate for all project
subsidiaries which execute energy services agreements.

     The management services agreement, if entered into at the effective time of
the merger, will be on substantially the same terms as CogenAmerica's existing
management services agreement with NRG. The management services agreement
provides that Calpine will provide management, administrative, operation,
maintenance and certain other services to CogenAmerica in connection with
CogenAmerica's day to day business.

     The operating and maintenance agreement for the Morris, Illinois, Newark,
New Jersey and Parlin, New Jersey projects, if entered into at the effective
time of the merger, will be on substantially the same terms as CogenAmerica's
existing operating and maintenance agreements with NRG for such projects. The
operating and maintenance agreement for the Pryor, Oklahoma project, if entered
into at the effective time of the merger, will be in a form previously agreed to
by Calpine and NRG.

     Directors and Officers of Cogenamerica. Four members of the CogenAmerica
Board of Directors were officers of NRG as of the date the CogenAmerica Board of
Directors approved the merger agreement. David H. Peterson, a director and
Chairman of CogenAmerica, is Chairman of the Board, President and Chief
Executive Officer of NRG. Craig A. Mataczynski, a director of CogenAmerica, is
the President and Chief Executive Officer of NRG's North America Division.
Ronald J. Will, a director of CogenAmerica, is the Managing Director and Chief
Executive Officer of NRG's European operations. Michael O'Sullivan, a director
of CogenAmerica, was a Vice President NRG's North America Division until he
resigned effective September 3, 1999 to accept a position with a party not
affiliated with NRG. Messrs. Peterson, Mataczynski and Will each hold options to
acquire 30,000 shares of CogenAmerica common stock at an exercise price of
$5.4375 per share. NRG has advised CogenAmerica that current NRG corporate
policy prohibits NRG employees, including Messrs. Peterson, Mataczynski and
Will, from receiving the economic benefit of the options granted to them in
their capacities as directors of

                                       32
<PAGE>   41

CogenAmerica. Current NRG corporate policy prohibits NRG employees from
receiving the economic benefit of options granted to them in their capacity as a
director of an affiliated company. The NRG employees who serve as directors of
CogenAmerica and were previously granted stock options in their capacity as
directors of CogenAmerica, have agreed to the cancellation of their stock
options. The amount of NRG's required contribution into Acquisition Sub will be
reduced by the amount determined by multiplying (i) the number of cancelled
options by (ii) the excess of $25.00 over the exercise prices for the options,
thereby ensuring that NRG receives credit equal to the value of the cancelled
options by the Board members who are employees of NRG. The NRG employees who
serve as directors of CogenAmerica and whose options have been cancelled will
receive no cash payment for these options. Julie A. Jorgensen, a director and
the President and Chief Executive Officer of CogenAmerica, owns 1,500 shares of
CogenAmerica common stock and has options to purchase 30,000 shares of
CogenAmerica common stock at $9.125 per share and 200,000 shares of CogenAmerica
common stock at $11.5625 per share, including 100,000 shares which will become
vested and exercisable as a result of the completion of the merger. The three
disinterested directors who comprise the Independent Directors Committee are
Mark Liddell, Lawrence I. Littman and Charles T. Thayer. CogenAmerica has a
policy of granting options to non-employee directors. Mr. Liddell who was
elected as a director at the 1999 annual meeting has an option to acquire 10,000
shares of CogenAmerica common stock at $12.375 per share which will become
vested and exercisable upon completion of the merger. Mr. Littman owns 70 shares
of CogenAmerica common stock and has options to acquire 30,000 shares at an
exercise price of $5.4375 per share. Mr. Thayer owns 20,000 shares of
CogenAmerica common stock and has options to acquire 10,000 shares at an
exercise price of $5.4375 per share. A description of the value of options for
each executive officer is included under "Interests in Securities of
CogenAmerica" (page   ).

     Severance Agreements for Officers. Under the employment agreement dated May
1, 1999 between CogenAmerica and Ms. Jorgensen, Ms. Jorgensen will be entitled
to terminate her employment after completion of the merger and receive a lump
sum severance payment equal to her base annual salary ($200,000) plus her
current annual target bonus ($100,000) for a total payment of $300,000. On June
11, 1999, the Compensation Committee of the CogenAmerica Board of Directors
adopted a severance policy for designated employees, including officers other
than Ms. Jorgensen, that provides the following severance in the event of a
termination of employment for any reason after the merger: (1) the payment in a
lump sum of the balance of the employee's 1999 base salary and target bonus or
maximum bonus depending upon the timing of the payment elected by the employee;
(2) the payment in a lump sum of the employee's base salary for a specified
period that is 12 months for officers of CogenAmerica, and (3) continuation of
health, dental, life and disability insurance benefits for the severance period.
Assuming that the merger and termination of employment occurs on December 15,
1999, officers of CogenAmerica other than Ms. Jorgensen would receive the
following payments for salary and bonus: $278,092 (target bonus) or $459,292
(maximum bonus) to Timothy P. Hunstad, Vice President and Chief Financial
Officer; $307,558 (target bonus) or $507,958 (maximum bonus) to Richard C.
Stone, Vice President -- Business Development and Marketing; and $208,125
(target bonus) or $329,625 (maximum bonus) to Thomas L. Osteraas, General
Counsel and Secretary.

     Indemnification. The bylaws of CogenAmerica provide for the indemnification
of its directors and officers against expenses and liabilities in connection
with any proceeding by

                                       33
<PAGE>   42

reason of his or her being or having been a director or officer. The merger
agreement provides that for six years after the merger, Calpine will cause
CogenAmerica to indemnify all past and present officers and directors of
CogenAmerica and its subsidiaries to the same extent as is indemnified at the
date of the merger agreement for acts or omissions occurring at or prior to the
merger. Calpine also agreed to provide, or cause CogenAmerica as the surviving
corporation in the merger, for not less than six years after the merger, a
directors' and officers' insurance and indemnification policy providing coverage
for events occurring prior to the merger with coverage substantially similar to
CogenAmerica's existing policy or, if substantially similar coverage is
unavailable, then best available coverage. Calpine and CogenAmerica are not
collectively required to pay premiums of more than $360,000 in any calendar
year.

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<PAGE>   43

                   SUMMARY OF MATERIAL FEATURES OF THE MERGER

THE MERGER

     General. The merger agreement provides that, subject to its conditions and
in accordance with the DGCL, Acquisition Sub will be merged into CogenAmerica
when a certificate of merger is filed with the Delaware Secretary of State or
such other date or time as is stated in the certificate of merger. Following the
merger, the separate existence of Acquisition Sub will cease, and CogenAmerica
will continue as the surviving corporation. At the effective time, each issued
and outstanding share of CogenAmerica common stock, other than shares owned by
CogenAmerica, by Acquisition Sub or by stockholders who exercise their appraisal
rights, will be converted into the right to receive, upon surrender of the
certificate formerly representing the shares of CogenAmerica common stock (the
"Certificate"), $25.00 in cash. As a result of the merger, the CogenAmerica
common stock will no longer be publicly traded and the equity of the surviving
corporation will be owned 80% by Calpine and 20% by NRG.

     Merger Consideration. When the merger is completed, each share of
CogenAmerica common stock issued and outstanding immediately prior to the
effective time of the merger will no longer be outstanding and will
automatically be canceled and retired. Each holder of a Certificate will have
only the right to receive an amount in cash equal to the number of such shares
multiplied by $25.00 per share at the time the Certificate is surrendered.

     Payment for Shares. As soon as practicable, after the effective time,
America Stock Transfer Company (the "Payment Agent") will mail to each holder of
record of a Certificate a form of letter of transmittal which instructs
CogenAmerica stockholders how to surrender their shares of CogenAmerica common
stock and receive the merger consideration. Risk of loss and title to the
Certificate will pass only when the Payment Agent receives delivery. When a
record holder has delivered to the Payment Agent all Certificates for its shares
of CogenAmerica common stock together with the duly executed letter of
transmittal, the Payment Agent will issue a check for the merger consideration,
net of any withholding or other taxes, if applicable, and mail the check to the
record holder.

     Stock Options. The merger agreement provides that at the effective time of
the merger all options to purchase CogenAmerica common stock will be canceled
and each holder of an option will have the right to receive, upon execution and
delivery to the Payment Agent of an option termination agreement, with respect
to his or her options, a cash payment equal to (a) the excess, if any, of $25.00
over the exercise price of his or her options, multiplied by (b) the total
number of shares of CogenAmerica common stock for which such options are then
vested and exercisable (after giving effect to any acceleration of vesting as a
result of the consummation of the merger) pursuant to the terms of such options.
The payment of the consideration for an option, net of any withholding or other
applicable taxes, upon delivery to the Payment Agent of an option termination
agreement, will constitute full satisfaction of all rights pertaining to the
option.

     Closing of Transfer Books. At the effective time of the merger, the stock
transfer books of CogenAmerica will be closed and no further transfer of shares
of CogenAmerica common stock will be made on the records of CogenAmerica. On or
after the effective time, any Certificates presented to the surviving
corporation or the Payment Agent will be canceled and exchanged for the merger
consideration.

                                       35
<PAGE>   44

CONDITIONS TO THE MERGER.

     Each party's obligation to complete the merger is conditioned upon the
following: (a) adoption and approval of the merger agreement by the vote of the
holders of more than 66 2/3% of the outstanding shares of the CogenAmerica
common stock, (b) approval of the charter amendment by the vote of the holders
of more than 50% of the outstanding shares of CogenAmerica common stock, (c)
expiration or termination of the waiting period (and any extension thereof)
applicable to the merger under the HSR Act, (d) the obtaining of all
authorizations, consents, orders, declarations or approvals of, or filings with,
or terminations or expirations of waiting periods imposed by, any governmental
entity, the failure of which would have the effect of making the merger or any
transaction described in the merger agreement illegal or would have,
individually or in the aggregate, a material adverse effect on Calpine (assuming
the merger has taken place), and (e) the absence of any statute, rule,
regulation, legislation, interpretation, judgment, order or injunction or other
action (i) challenging the acquisition by Calpine or Acquisition Sub of any
CogenAmerica common stock, (ii) seeking to prohibit or limit the ownership or
operation by CogenAmerica, Calpine or any of their respective subsidiaries of
any material portion of the business or assets of CogenAmerica, Calpine or any
of their respective subsidiaries, or to compel CogenAmerica, Calpine or any of
their respective subsidiaries to dispose of or hold separate any material
portion of the business or assets of CogenAmerica, Calpine or any of their
respective subsidiaries, (iii) seeking to impose limitations on the ability of
Calpine or Acquisition Sub to acquire or hold, or exercise full rights of
ownership of, any shares of CogenAmerica common stock, including the right to
vote the CogenAmerica common stock purchased by it on all matters properly
presented to the stockholders of CogenAmerica, (iv) seeking to prohibit Calpine
or any of its subsidiaries from effectively controlling in any material respect
the business or operations of CogenAmerica and its subsidiaries in connection
with the merger or the merger agreement, or (v) which otherwise is reasonably
likely to have a material adverse effect on CogenAmerica.

     The obligation of CogenAmerica to complete the merger is subject to the
satisfaction of the following conditions at or prior to the effective time: (a)
each of Calpine and Acquisition Sub has performed in all material respects each
of its agreements contained in the merger agreement and the representations and
warranties of Calpine and Acquisition Sub contained in the merger agreement are
true and complete except for such exceptions as would not have a material
adverse effect on Calpine; and (b) no governmental entity has imposed any
requirement which, individually or in the aggregate, would have a material
adverse effect on Calpine.

     The obligations of Calpine and Acquisition Sub to complete the merger are
subject to the satisfaction of the following conditions at or prior to the
effective time: (a) CogenAmerica shall have complied with covenants regarding
conduct of CogenAmerica's business in the merger agreement and complies with its
agreements and covenants contained in the merger agreement in all material
respects and the representations and warranties of CogenAmerica contained in the
merger agreement shall be true and complete except for such exceptions as would
not have a material adverse effect on CogenAmerica; (b) there shall not be
instituted or pending any suit, action or proceeding initiated as a result of
the merger agreement or any transactions contemplated thereby (i) challenging
the acquisition by Calpine or Acquisition Sub of any CogenAmerica common stock,
seeking to restrain or prohibit the making or consummation of the merger or any
other transaction, (ii) seeking to prohibit or limit the ownership or operation
by CogenAmerica, Calpine or any of their respective subsidiaries of any material

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<PAGE>   45

portion of the business or assets of CogenAmerica, Calpine or any of their
respective subsidiaries, or to compel CogenAmerica, Calpine or any of their
respective subsidiaries to dispose of or hold separate any material portion of
the business or assets of CogenAmerica, Calpine or any of their respective
subsidiaries, (iii) seeking to impose limitations on the ability of Calpine or
Acquisition Sub to acquire or hold, or exercise full rights of ownership of, any
shares of CogenAmerica common stock, including the right to vote CogenAmerica
common stock purchased by it on all matters properly presented to the
CogenAmerica stockholders, (iv) seeking to prohibit Calpine or any of its
subsidiaries from effectively controlling in any material respect the business
or operations of CogenAmerica and its subsidiaries in connection with the merger
or the merger agreement, or (v) which otherwise is reasonably likely to have a
material adverse effect on CogenAmerica; and (c) since the date of the merger
agreement, there shall not have occurred any event, change, effect or
development that, individually or in the aggregate, has had or would be
reasonably expected to have a material adverse effect on CogenAmerica.

     EVEN IF THE COGENAMERICA STOCKHOLDERS APPROVE AND ADOPT THE MERGER
AGREEMENT, THERE CAN BE NO ASSURANCE THAT THE MERGER WILL BE COMPLETED.

     Representations and Warranties. CogenAmerica made representations and
warranties in the merger agreement, qualified in certain instances by
materiality or as disclosed in CogenAmerica's disclosure letter (the
"CogenAmerica Letter") regarding the following: its organization and good
standing; authority to enter into the merger agreement and complete the
transactions contemplated by the merger agreement; the capital structure of
CogenAmerica and its subsidiaries; the non-contravention of the merger agreement
with CogenAmerica's certificate of incorporation, Bylaws, any contract or law;
requisite governmental and other consents and approvals; compliance with the SEC
filing requirements; its financial statements; the accuracy of information in
this proxy statement and compliance with the Exchange Act; the absence of
certain material changes since December 31, 1998; possession of permits and
compliance with governing documents and laws; absence of undisclosed material
contracts; absence of material events of default or basis for material events of
default; requisite tax filings and examinations; absence of outstanding orders,
judgments, injunctions and similar actions and absence of disputes involving
CogenAmerica or its subsidiaries or their businesses; agreements relating to
certain employment, consulting and benefit matters of CogenAmerica; compliance
with worker safety, labor and employment and environmental laws; absence of
state takeover laws applicable to CogenAmerica; the required vote of
stockholders of CogenAmerica necessary to approve the merger agreement; absence
of brokers or similar fees other than to DLJ; the receipt of the DLJ fairness
opinion; the applicability and compliance with certain utility regulations;
insurance coverage; and related party transactions.

CERTAIN COVENANTS.

     Until the merger is completed, CogenAmerica has agreed that CogenAmerica
and its subsidiaries will conduct their business in the ordinary course and use
their best efforts to preserve their current business organizations, keep
available the services of its current officers and employees and preserve their
third party relationships.

     CogenAmerica has also agreed that, without the consent of Calpine unless
contemplated by the CogenAmerica disclosure, neither CogenAmerica nor its
subsidiaries will: (a) declare or pay any dividend on or make any other
distribution in respect of its

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<PAGE>   46

capital stock, or split, combine or reclassify any class of stock or purchase,
redeem or acquire any shares of capital stock; (b) issue or encumber any shares
of its capital stock or other securities other than the issuance of shares of
CogenAmerica common stock upon the exercise of options; (c) amend its governing
documents; (d) acquire by merger or consolidation or asset purchase or equity
purchase any entity or division other than transactions in the ordinary course
of business consistent with past practice and that have a transaction value of
less than $250,000 individually or $1,000,000 in the aggregate and which are not
material to CogenAmerica; (e) sell or otherwise dispose of assets other than in
the ordinary course of business consistent with past practice and that have a
transaction value of less than $250,000 individually or $1,000,000 in the
aggregate; (f) incur indebtedness for borrowed money or make loans or
investments, except for obligations incurred in the ordinary course of business
consistent with past practice that are less than $500,000 in the aggregate and
transactions between or among CogenAmerica and its subsidiaries; (g) alter the
corporate structure or ownership of CogenAmerica or its subsidiaries; (h) adopt
or amend existing benefit plans, severance plans or employment or consulting
agreements, except for immaterial changes as required by applicable law; (i)
increase compensation to directors, officers, employees, independent contractors
or consultants, grant severance or termination pay or enhance or accelerate
rights under any plan or arrangement for the benefit of any director, officer,
employee, independent contractor or consultant; (j) violate or fail to perform
any obligation imposed by material federal, state or local law rule or
regulation; (k) change any accounting policies or procedures, except as required
to by generally accepted accounting principles; (l) file tax returns
inconsistent with past practice or take any position inconsistent with prior
positions; (m) make tax elections or settle or compromise any material tax
liability; (n) enter into or amend any contract which involves aggregate
payments in excess of $250,000 for individual contracts or $1,000,000 in the
aggregate for all contracts or make or agree to make new capital expenditures in
excess of $250,000 individually or $500,000 in the aggregate; or (o) pay or
discharge any obligations other than the payment or discharge of obligations in
the ordinary course of business consistent with past practice that are reflected
in or as contemplated by the most recent financial statements, or certain
payments of indebtedness owed by CogenAmerica or a subsidiary under an existing
credit facility.

NO SOLICITATION OF TRANSACTIONS.

     The merger agreement provides that CogenAmerica will not, directly or
indirectly (a) solicit, initiate or encourage the submission of any Takeover
Proposal (as defined below), (b) enter into any agreement with respect to any
Takeover Proposal, or (c) participate in any discussions or negotiations
regarding, or furnish to any person any information with respect to, or take any
other action to facilitate any inquiries or the making of any proposal that
constitutes, or may reasonably be expected to lead to, any Takeover Proposal. If
the CogenAmerica Board of Directors reasonably determines the Takeover Proposal
constitutes a Superior Proposal (as defined below), then, to the extent required
by the fiduciary obligations of the CogenAmerica Board of Directors, as
determined in good faith by a majority of the disinterested members after
receiving the advice of independent legal counsel, CogenAmerica may, in response
to an unsolicited request, furnish information with respect to CogenAmerica to,
and enter into discussions with, any person that has made such a Takeover
Proposal pursuant to a customary confidentiality agreement.

     The merger agreement defines a "Takeover Proposal" to mean any proposal for
a merger or other business combination involving CogenAmerica or any of its
subsidiaries or

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<PAGE>   47

any proposal or offer to acquire in any manner, directly or indirectly, a
substantial equity interest in, a substantial portion of the voting securities
of, or a substantial portion of the assets of CogenAmerica or any of its
subsidiaries, other than the transactions contemplated by the merger agreement.
A "Superior Proposal" means a bona fide Takeover Proposal made by a third party
which a majority of the disinterested members of the CogenAmerica Board of
Directors determines in its reasonable good faith judgment to be more favorable
to CogenAmerica's stockholders than the merger, and for which financing, to the
extent required, is then committed or which, in the reasonable good faith
judgment of a majority of such disinterested members is highly likely to be
financed by the third party. In making these determinations and judgments, the
CogenAmerica Board of Directors must receive a written opinion from an
independent financial advisor of nationally recognized reputation that the value
of the consideration provided for in the alternative proposal exceeds the value
of the consideration provided for in the merger and written advice as to the
likelihood of the third party obtaining any necessary financing.

     The merger agreement requires CogenAmerica to advise Calpine of (a) any
Takeover Proposal or inquiry with respect to or which could lead to any Takeover
Proposal, (b) the material terms of such Takeover Proposal, and (c) the identity
of the person making any such Takeover Proposal or inquiry. The merger agreement
also requires CogenAmerica to keep Calpine fully informed of the status and
details of any such Takeover Proposal or inquiry.

TERMINATION.

     The merger agreement may be terminated at any time prior to the effective
time, whether before or after approval of the matters presented in connection
with the merger by the stockholders of CogenAmerica:

          1. by mutual written consent of Calpine and CogenAmerica; or

          2. by either Calpine or CogenAmerica if the other party fails to
     comply in any material respect with any of its covenants or agreements in
     the merger agreement, and the failure is not cured within 30 business days
     following receipt of notice; or

          3. by either Calpine or CogenAmerica if there has been a breach by the
     other party (in the case of Calpine including a material breach by
     Acquisition Sub) of any representation or warranty that would have a
     material adverse effect on the breaching party or would prevent the
     breaching party from consummating the merger; or

          4. by either Calpine or CogenAmerica if the merger has not been
     effected on or prior to the later of (a) February 28, 2000 or, if the sole
     reason that the merger has not been consummated by February 28, 2000 is
     that the special meeting has not been held by such date, or (b) March 31,
     2000, in either case for a reason other than the failure of the terminating
     party to comply with its obligations under the merger agreement; or

          5. by either Calpine or CogenAmerica if any court or other
     governmental entity having jurisdiction has issued an order or taken other
     action permanently enjoining or otherwise prohibiting the transactions
     contemplated by the merger agreement and such action has become final and
     nonappealable; or

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<PAGE>   48

          6. by either Calpine or CogenAmerica if the stockholders of
     CogenAmerica do not approve the merger agreement at the special meeting or
     any adjournment or postponement thereof; or

          7. by CogenAmerica if concurrently with or immediately after such
     termination, CogenAmerica enters into a merger, acquisition or other
     agreement to affect a Superior Proposal and prior to such termination
     CogenAmerica has (a) delivered to Calpine a written notice of intent to
     enter into an agreement to effect a Superior Proposal, (b) four business
     days have elapsed following the notice, (c) CogenAmerica informed Calpine
     of the terms and conditions of the Takeover Proposal and the identity of
     the person making the proposal, (d) the CogenAmerica Board of Directors has
     continued reasonably to believe following the notice period that the
     Takeover Proposal constitutes a Superior Proposal after taking into account
     any amendment of the terms of the merger by Calpine or any proposal by
     Calpine to amend the terms of the merger agreement, the merger or any other
     Takeover Proposal made by Calpine, and (e) CogenAmerica has paid Calpine a
     termination fee of $7,500,000; or

          8. by Calpine if prior to the effective time the CogenAmerica Board of
     Directors or any committee thereof shall have withdrawn or modified in a
     manner adverse to Calpine or Acquisition Sub its approval or recommendation
     of the merger or shall have recommended or approved a Superior Proposal, or
     shall have resolved to do any of the foregoing.

TERMINATION FEE.

     If (a) the merger agreement is terminated pursuant to paragraph 7 of the
preceding section entitled "-- Termination" or (b) if (i) the merger agreement
is terminated by (A) CogenAmerica or Calpine pursuant to paragraph 6 of the
preceding section or (B) by Calpine pursuant to paragraphs 2, 3 or 8 of the
preceding section, (ii) prior to such termination any person makes a Takeover
Proposal, and (iii) concurrently with or within 12 months after such a
termination a Third Party Acquisition Event (as defined below) occurs, in each
case CogenAmerica will be obligated to pay to Calpine a termination fee of
$7,500,000 in cash (the "Termination Fee").

     A "Third Party Acquisition Event" occurs when, pursuant to a legally
binding definitive agreement or agreement in principal with CogenAmerica, any
person, entity or group (other than Calpine, Acquisition Sub or any of their
affiliates), in one or a series of transactions, acquires more than 50% of the
outstanding CogenAmerica common stock or assets of CogenAmerica through open
market purchases, merger, consolidation, tender or exchange offer,
reorganization or other business combination.

     Indemnification. The merger agreement provides that for six years from the
effective time, Calpine will cause the surviving corporation to indemnify and
hold harmless all past and present officers and directors of CogenAmerica to the
same extent as such persons are indemnified at the date of the merger agreement
for acts or omissions occurring at or prior to the effective time. Calpine has
agreed to provide, or cause the surviving corporation to provide, for not less
than six years from the effective time a directors and officers insurance and
indemnification policy providing coverage for events occurring prior to the
effective time with coverage substantially similar to CogenAmerica's existing
policy or if substantially similar coverage is unavailable, then best available,
provided that Calpine shall not be required to pay premiums aggregating more
than $360,000 in any calendar year.

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<PAGE>   49

     Amendment and Waiver. The merger agreement may be amended pursuant to
action taken or authorized by the respective Boards of Directors of Calpine and
CogenAmerica at any time prior to or after approval of the merger agreement by
the stockholders of CogenAmerica but, after such approval, no amendment will be
made without the further approval of the stockholders if further approval is
required by law. At any time prior to the effective time, any of the parties to
the merger agreement may extend, in writing, the time for performance of any
obligations or other acts of the other party, waive any inaccuracies in the
representations and warranties contained in the merger agreement or any document
delivered pursuant to the merger agreement and waive compliance with any of the
agreements or conditions contained in the merger agreement.

     Expenses. Whether or not the merger is consummated, all costs and expenses
incurred in connection with the merger agreement and the transactions
contemplated thereby will be paid by the party incurring such expense.

EFFECTIVE TIME

     The merger will become effective at the effective time. It is expected that
the effective time will be the date of closing of the merger, which is expected
to be December   , 1999, or as soon thereafter as is practicable subject to
satisfaction or waiver of the conditions to closing.

CONVERSION OF COMMON STOCK

     As of the effective time, each share of CogenAmerica common stock issued
and outstanding immediately prior to the effective time of the merger (other
than shares owned by CogenAmerica, by Acquisition Sub or by stockholders who
properly exercise their appraisal rights under the DGCL) will be converted into
the right to receive the merger consideration when the Certificate formerly
representing such share of CogenAmerica common stock is surrendered and a duly
executed letter of transmittal is delivered to the Payment Agent. The Payment
Agent will mail to each record holder of CogenAmerica common stock, as soon as
practicable after the effective time of the merger, a letter of transmittal
which will contain instructions for surrendering the Certificates for
CogenAmerica common stock in exchange for the merger consideration. When so
converted, all such shares of CogenAmerica common stock will no longer be
outstanding and will automatically be canceled and retired and each holder of a
Certificate formerly representing any such shares will have only the right to
receive the merger consideration in cash (without interest) upon the surrender
of the Certificate. Holders of options will receive payment in accordance with
the procedures described below under "Payment for Stock Options."

     As soon as practicable after the effective time of the merger, Calpine will
deposit with the Payment Agent, in trust for the holders of the CogenAmerica
common stock converted in the merger and holders of options, an amount of cash
equal to or exceeding the aggregate merger consideration and the consideration
for the options, net of any withholding or other taxes, if applicable.

     COGENAMERICA'S STOCKHOLDERS SHOULD NOT FORWARD THEIR STOCK CERTIFICATES TO
THE PAYMENT AGENT WITHOUT A LETTER OF TRANSMITTAL. STOCK CERTIFICATES SHOULD NOT
BE RETURNED WITH THE ENCLOSED PROXY CARD.

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<PAGE>   50

     The payment of the merger consideration, net of any withholding or other
taxes, if applicable, upon surrender of any Certificate will be deemed to
constitute full satisfaction of all rights pertaining to the shares of
CogenAmerica common stock represented by the Certificate. Until surrendered as
contemplated by the merger agreement, each Certificate for CogenAmerica common
stock will be deemed at any time after the effective time to represent only the
right to receive the merger consideration upon surrender; no interest will be
paid or will accrue on any merger consideration payable to stockholders. At the
effective time of the merger, the stock transfer books of CogenAmerica will be
closed. Neither Calpine nor the surviving corporation will be liable to any
former stockholder or holder of a option for any cash held in the payment fund
which is delivered to a public official pursuant to any applicable abandoned
property, escheat or similar law.

PAYMENT FOR STOCK OPTIONS

     Each option to purchase CogenAmerica common stock which is outstanding
immediately prior to the effective time of the merger will be canceled, and the
holder will have the right to receive, upon execution and delivery to the
Payment Agent of an option termination agreement, a cash payment equal to the
(a) excess of $25.00 over the exercise price of the option, multiplied by (b)
the total number of shares of CogenAmerica common stock for which such options
are then vested and exercisable (after giving effect to any acceleration of
vesting as a result of the consummation of the merger) pursuant to the terms of
such options. The payment of the consideration for an option, net of any
withholding or other applicable taxes, upon delivery to the Payment Agent of an
option termination agreement signed by the holder of the option, will constitute
full satisfaction of all rights pertaining to the option.

CONDUCT OF BUSINESS PENDING THE MERGER

     Pursuant to the merger agreement, CogenAmerica has agreed to carry on its
business prior to the effective time of the merger in all material respects in
the ordinary course of its business as conducted on the date of the merger
agreement, subject to certain covenants by CogenAmerica in the merger agreement.

REGULATORY FILINGS AND APPROVALS

     CogenAmerica believes that the following filings or approvals are required
with respect to the merger: (a) filings with and approvals of the FERC, (b)
filings by CogenAmerica and Calpine with the Federal Trade Commission and the
Department of Justice pursuant to the requirements of the HSR Act, (c) filings
by CogenAmerica, Calpine, Acquisition Sub and NRG with the SEC pursuant to the
Exchange Act, (d) filings by CogenAmerica under the New Jersey Industrial Site
Recovery Act, (e) filing the certificate of amendment to effect the charter
amendment with the Delaware Secretary of State, and (e) filing of the
certificate of merger to effect the merger with the Delaware Secretary of State.

CONDITIONS TO THE MERGER

     The obligations of Calpine, Acquisition Sub and CogenAmerica to effect the
merger are subject to the fulfillment of certain conditions described more fully
under "Summary of Material Features of the Merger Agreement -- Conditions to the
Merger" (page      ).

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<PAGE>   51

FEDERAL INCOME TAX CONSEQUENCES OF THE TRANSACTION

     The following discussion summarizes the material federal income tax
considerations relevant to the merger that are generally applicable to holders
of CogenAmerica common stock and those options to purchase CogenAmerica common
stock that were granted by CogenAmerica or any of its subsidiaries as
compensation for services. This discussion is based on currently existing
provisions of the Internal Revenue Code, existing and proposed Treasury
Regulations and current administrative rulings and court decisions, all of which
are subject to change. Any change, which may or may not be retroactive, could
alter the tax consequences to the holders of the CogenAmerica common stock or
options as described here. Special tax consequences not described below may be
applicable to particular classes of taxpayers, including financial institutions,
broker-dealers, persons who are not citizens or residents of the United States
or who are foreign corporations, foreign partnerships or foreign estates or
trusts and stockholders who acquired CogenAmerica common stock through the
exercise of options or otherwise as compensation prior to the effective time of
the merger.

     The conversion of the CogenAmerica common stock at the effective time of
the merger into the right to receive the merger consideration of $25.00 per
share in cash will be a taxable transaction for federal income tax purposes and
may also be a taxable transaction under applicable state and other tax laws. In
general, a stockholder will recognize gain or loss equal to the difference
between the tax basis of the CogenAmerica common stock and the amount of merger
consideration received in exchange for the CogenAmerica common stock. The gain
or loss will be treated as capital gain or loss if the CogenAmerica common stock
is a capital asset in the hands of the stockholder.

     The receipt of the consideration for options (that were granted by
CogenAmerica or any of its subsidiaries as compensation for services) upon
delivery to the Payment Agent of an option termination agreement will be taxable
as ordinary income for federal and state income and other tax purposes. The
consideration for such options will be paid to the holders of such options net
of withholding and other applicable taxes.

     The federal income tax consequences set forth above are for general
information only. Each stockholder and each holder of options is urged to
consult his or her own tax advisor to determine the particular tax consequences
to him or her of the merger, including the applicability and effect of state and
other tax laws.

FINANCING OF THE MERGER; SOURCE OF FUNDS

     Calpine has represented in the merger agreement that it has sufficient
capital resources necessary to perform its obligations under the merger
agreement. Calpine intends to finance the transaction with working capital funds
and borrowings under existing credit facilities.

ANTICIPATED ACCOUNTING TREATMENT

     CogenAmerica believes that the merger will be accounted for by Calpine
using the purchase method of accounting in accordance with generally accepted
accounting principles.

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<PAGE>   52

APPRAISAL RIGHTS

     If the merger is consummated, holders of shares of CogenAmerica common
stock are entitled to appraisal rights under Section 262 of the DGCL, provided
that they comply with the conditions established by Section 262.

     Section 262 is reprinted in its entirety as Appendix D to this proxy
statement. The following discussion is not a complete statement of the law
relating to appraisal rights and is qualified in its entirety by reference to
Appendix D. This discussion and Appendix D should be reviewed carefully by any
stockholder who wishes to exercise statutory appraisal rights or who wishes to
preserve the right to do so, as failure to comply with the procedures set forth
herein or therein will result in the loss of appraisal rights.

     A record holder of shares of CogenAmerica common stock who makes the demand
described below with respect to such shares, who continuously is the record
holder of such shares through the effective time of the merger, who otherwise
complies with the statutory requirements of Section 262 and who neither votes in
favor of the merger nor consents thereto in writing will be entitled, in lieu of
the $25.00 cash per share of CogenAmerica common stock to be paid in the merger,
to an appraisal by the Delaware Court of Chancery (the "Delaware Court") of the
fair value of his or her shares of CogenAmerica common stock. All references in
this summary of appraisal rights to a "stockholder" or "holders of shares of
common stock" are to the record holder or holders of shares of CogenAmerica
common stock. Except as set forth herein, stockholders of CogenAmerica will not
be entitled to appraisal rights in connection with the merger.

     VOTING AGAINST, ABSTAINING FROM VOTING OR FAILING TO VOTE ON APPROVAL AND
ADOPTION OF THE MERGER WILL NOT CONSTITUTE A DEMAND FOR APPRAISAL WITHIN THE
MEANING OF SECTION 262 OF THE DGCL.

     Under Section 262, where a merger is to be submitted for approval at a
meeting of stockholders, such as the special meeting, not less than 20 days
prior to the meeting a constituent corporation must notify each of the holders
of its stock for whom appraisal rights are available that such appraisal rights
are available and include in each such notice a copy of Section 262. This proxy
statement constitutes such notice to the record holders of CogenAmerica common
stock.

     Holders of shares of CogenAmerica common stock who desire to exercise their
appraisal rights must not vote in favor of the merger and must deliver a
separate written demand for appraisal to CogenAmerica prior to the vote by the
stockholders of CogenAmerica on the merger. A demand for appraisal must be
executed by or on behalf of the stockholder of record and must reasonably inform
CogenAmerica of the identity of the stockholder of record and that such
stockholder intends thereby to demand appraisal of the CogenAmerica common
stock. A proxy or vote against the merger will not by itself constitute such a
demand. Within ten days after the effective time of the merger, CogenAmerica
must provide notice of the effective time of the merger to all stockholders who
have complied with Section 262.

     A stockholder who elects to exercise appraisal rights should mail or
deliver his or her written demand to: Cogeneration Corporation of America,
Attention: Thomas L. Osteraas, General Counsel and Secretary, One Carlson
Parkway, Suite 240, Minneapolis, Minnesota, 55447-4454.

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<PAGE>   53

     A person having a beneficial interest in shares of CogenAmerica common
stock that are held of record in the name of another person, such as a broker,
fiduciary, depositary or other nominee, must act promptly to cause the record
holder to follow the steps summarized herein properly and in a timely manner to
perfect appraisal rights. If the shares of CogenAmerica common stock are owned
of record by a person other than the beneficial owner, including a broker,
fiduciary (such as a trustee, guardian or custodian), depositary or other
nominee, such demand must be executed by or for the record owner. If the shares
of CogenAmerica common stock are owned of record by more than one person, as in
a joint tenancy or tenancy in common, such demand must be executed by or for all
joint owners. An authorized agent, including an agent for two or more joint
owners, may execute the demand for appraisal for a stockholder of record;
however, the agent must identify the record owner and expressly disclose the
fact that, in exercising the demand, such person is acting as agent for the
record owner. If a stockholder holds shares of CogenAmerica common stock through
a broker who in turn holds the shares through a central securities depository
nominee such as Cede & Co., a demand for appraisal of such shares must be made
by or on behalf of the depository nominee and must identify the depository
nominee as record holder.

     A record holder, such as a broker, fiduciary, depositary or other nominee
who holds shares of CogenAmerica common stock as a nominee for others, may
exercise appraisal rights with respect to the shares held for all or less than
all beneficial owners of shares as to which such person is the record owner. In
such case, the written demand must set forth the number of shares covered by
such demand. Where the number of shares is not expressly stated, the demand will
be presumed to cover all shares of CogenAmerica common stock outstanding in the
name of such record owner.

     Within 120 days after the effective time of the merger, either CogenAmerica
or any stockholder who has complied with the required conditions of Section 262
may file a petition in the Delaware Court, with a copy served on CogenAmerica in
the case of a petition filed by a stockholder, demanding a determination of the
fair value of the shares of all dissenting stockholders. There is no present
intent on the part of CogenAmerica to file an appraisal petition and
stockholders seeking to exercise appraisal rights should not assume that
CogenAmerica will file such a petition or that CogenAmerica will initiate any
negotiations with respect to the fair value of such shares. Accordingly, holders
of CogenAmerica common stock who desire to have their shares appraised should
initiate any petitions necessary for the perfection of their appraisal rights
within the time periods and in the manner prescribed in Section 262. Within 120
days after the effective time of the merger, any stockholder who has theretofore
complied with the applicable provisions of Section 262 will be entitled, upon
written request, to receive from CogenAmerica a statement setting forth the
aggregate number of shares of CogenAmerica common stock not voting in favor of
the merger and with respect to which demands for appraisal were received by
CogenAmerica and the number of holders of such shares. Such statement must be
mailed (i) within 10 days after the written request therefor has been received
by CogenAmerica or (ii) within 10 days after the expiration of the period for
the delivery of demands as described above, whichever is later.

     If a petition for an appraisal is filed timely, at the hearing on such
petition, the Delaware Court will determine which stockholders are entitled to
appraisal rights. The Delaware Court may require the stockholders who have
demanded an appraisal for their shares and who hold stock represented by
certificates to submit their certificates of stock to the Register in Chancery
for notation thereon of the pendency of the appraisal proceedings;

                                       45
<PAGE>   54

and if any stockholder fails to comply with such direction, the Delaware Court
may dismiss the proceedings as to such stockholder. Where proceedings are not
dismissed, the Delaware Court will appraise the shares of CogenAmerica common
stock owned by such stockholders, determining the fair value of such shares
exclusive of any element of value arising from the accomplishment or expectation
of the merger, together with a fair rate of interest, if any, to be paid upon
the amount determined to be the fair value.

     Although CogenAmerica believes that the merger consideration for each share
of CogenAmerica common stock held by a stockholder is fair, no representation is
made as to the outcome of the appraisal of fair value as determined by the
Delaware Court and stockholders should recognize that such an appraisal could
result in a determination of a value higher or lower than, or the same as, the
merger consideration. Moreover, CogenAmerica does not anticipate offering more
than the merger consideration to any stockholder exercising appraisal rights and
reserves the right to assert, in any appraisal proceeding, that, for purposes of
Section 262, the "fair value" of a share of CogenAmerica common stock is less
than the merger consideration. In determining "fair value," the Delaware Court
is required to take into account all relevant factors. In Weinberger v. UOP,
Inc. the Delaware Supreme Court discussed the factors that could be considered
in determining fair value in an appraisal proceeding, stating that "proof of
value by any techniques or methods which are generally considered acceptable in
the financial community and otherwise admissible in court" should be considered
and that "fair price obviously requires consideration of all relevant factors
involving the value of a company." The Delaware Supreme Court has stated that in
making this determination of fair value the court must consider market value,
asset value, dividends, earnings prospects, the nature of the enterprise and any
other facts which could be ascertained as of the date of the merger which throw
any light on future prospects of the merged corporation. Section 262 provides
that fair value is to be "exclusive of any element of value arising from the
accomplishment or expectation of the merger." In Cede & Co. v. Technicolor,
Inc., the Delaware Supreme Court stated that such exclusion is a "narrow
exclusion that does not encompass known elements of value," but which rather
applies only to the speculative elements of value arising from such
accomplishment or expectation. In Weinberger, the Delaware Supreme Court
construed Section 262 to mean that "elements of future value, including the
nature of the enterprise, which are known or susceptible of proof as of the date
of the merger and not the product of speculation, may be considered."

     Delaware courts have decided that the statutory appraisal remedy, depending
on factual circumstances, may or may not be a dissenter's exclusive remedy.
Several decisions by the Delaware courts have held that a controlling
stockholder has a fiduciary duty to the other stockholders which requires that
the merger be "entirely fair" to such other stockholders. In determining whether
a merger is fair to minority stockholders, the Delaware courts have considered
among other things, the type of and amount of consideration to be received by
stockholders and whether there was fair dealing among the parties. The Delaware
Supreme Court stated in Weinberger, that although the remedy ordinarily
available in a merger that is found not to be "fair" to minority stockholders is
the right to appraisal described above, such appraisal remedy may not be
adequate "in certain cases, particularly where fraud, misrepresentations,
self-dealing, deliberate waste of corporate assets, or gross and palpable
overreaching are involved,"and that in such cases the Delaware Court would be
free to fashion any form of appropriate relief.

     Stockholders considering seeking appraisal should recognize that the fair
value of their shares determined under Section 262 could be more than, the same
as or less than the

                                       46
<PAGE>   55

consideration they are entitled to receive pursuant to the merger agreement if
they do not seek appraisal of their shares. The Delaware Court will determine
the amount of interest, if any, to be paid on amounts to be received by persons
whose shares have been appraised. The cost of the appraisal proceeding may be
determined by the Delaware Court and taxed against the parties as the Delaware
Court deems equitable in the circumstances. However, costs do not include
attorneys' and expert witness fees. Each dissenting stockholder is responsible
for his or her attorneys' and expert witness expenses, although, upon
application of a dissenting stockholder of CogenAmerica, the Delaware Court may
order that all or a portion of the expenses incurred by any dissenting
stockholder in connection with the appraisal proceeding, including without
limitation, reasonable attorneys' fees and the fees and expenses of experts, be
charged pro rata against the value of all shares of stock entitled to appraisal.

     Any stockholder who has duly demanded appraisal in compliance with Section
262 will not, after the effective time of the merger, be entitled to vote for
any purpose any shares subject to such demand or to receive payment of dividends
or other distributions on such shares, except for dividends or distributions
payable to stockholders of record at a date prior to the effective time of the
merger.

     At any time within 60 days after the effective time of the merger, any
stockholder will have the right to withdraw such demand for appraisal and to
accept the terms offered in the merger; after this period, the stockholder may
withdraw such demand for appraisal only with the consent of CogenAmerica. If no
petition for appraisal is filled with the Delaware Court within 120 days after
the effective time of the merger, stockholders' rights to appraisal shall cease,
and all holders of shares of CogenAmerica common stock will be entitled to
receive the consideration offered pursuant to the merger agreement. Inasmuch as
CogenAmerica has no obligation to file a petition for an appraisal, and
CogenAmerica has no present intention to do so, any stockholder who desires such
a petition to be filed is advised to file it on a timely basis. Any stockholder
may withdraw such stockholders' demand for appraisal by delivering to
CogenAmerica a written withdrawal of his or her demand for appraisal and
acceptance of the merger consideration, except (i) that any such attempt to
withdraw made more than 60 days after the effective time of the merger will
require written approval of CogenAmerica and (ii) that no appraisal proceeding
in the Delaware Court shall be dismissed as to any stockholder without the
approval of the Delaware Court, and such approval may be conditioned upon such
terms as the Delaware Court deems just.

     A stockholder will fail to perfect his or her right of appraisal if he or
she (a) does not deliver a written demand for appraisal to CogenAmerica prior to
the vote for approval and adoption of the merger agreement, (b) votes his or her
shares of CogenAmerica common stock in favor of approval and adoption of the
merger agreement, (c) does not file a petition for appraisal within 120 days
after the effective time of the merger, or (d) delivers to the company both a
written withdrawal of his or her demand for appraisal and an acceptance of the
terms of the merger agreement, except that any such attempt to withdraw such
demand not made within 60 days after the effective time of the merger requires
the written approval of CogenAmerica. If any stockholder who properly demands
appraisal of such stockholder's shares of CogenAmerica common stock under
Section 262 fails to perfect, or effectively withdraws or loses, such
stockholder's right to appraisal, the shares of CogenAmerica common stock of
such stockholder will be converted into the right to receive $25.00 per share in
cash in accordance with the merger agreement.

                                       47
<PAGE>   56

     Cash received pursuant to the exercise of appraisal rights may be subject
to federal or state income tax. See "Federal Income Tax Consequences of the
Transaction" (page   ).

     ANY HOLDER OF COGENAMERICA COMMON STOCK WHO FAILS TO COMPLY FULLY WITH THE
STATUTORY PROCEDURE SUMMARIZED ABOVE WILL FORFEIT HIS OR HER APPRAISAL RIGHTS
UNDER THE DGCL AND WILL RECEIVE THE MERGER CONSIDERATION FOR HIS OR HER SHARES.
SEE APPENDIX D.

     IN VIEW OF THE COMPLEXITY OF THESE PROVISIONS IN THE DGCL, STOCKHOLDERS WHO
ARE CONSIDERING DISSENTING FROM THE APPROVAL AND ADOPTION OF THE MERGER
AGREEMENT AND EXERCISING THEIR RIGHTS UNDER SECTION 262 SHOULD CONSULT THEIR
LEGAL ADVISORS.

           SUMMARY OF MATERIAL FEATURES OF THE CALPINE/NRG AGREEMENT

     Concurrently with the execution of the merger agreement, Calpine,
Acquisition Sub and NRG entered into the Calpine/NRG Agreement on August 26,
1999. The Calpine/ NRG Agreement provides that, subject to the terms and
conditions thereof, immediately prior to the consummation of the merger:

     - NRG will contribute to Acquisition Sub a number of shares of CogenAmerica
       common stock equal in value to (i) at least 20% of the total equity value
       of CogenAmerica less (ii) the value of the CogenAmerica stock options
       held by NRG employees which have been or will be cancelled prior to the
       merger, in exchange for 20% of the ownership interest in Acquisition Sub;
       and

     - Calpine will contribute to Acquisition Sub cash equal to 80% of the total
       equity value of CogenAmerica in exchange for 80% of the ownership
       interest in Acquisition Sub. The total equity value of CogenAmerica is
       defined as the sum of (i) the total number of issued and outstanding
       shares of CogenAmerica common stock immediately prior to completion of
       the merger multiplied by $25.00 and (ii) the aggregate amount of the
       excess of $25.00 per share over the exercise price per share of each of
       the outstanding CogenAmerica options.

     Pursuant to the Calpine/NRG Agreement, Calpine has also agreed to
contribute cash, in the form of a loan, sufficient to satisfy certain
obligations of CogenAmerica. Upon consummation of the merger, NRG shall own 20%
and Calpine shall own 80% of the outstanding shares of CogenAmerica common
stock. The obligations of Calpine and NRG to make their respective capital
contributions described above is conditioned upon the satisfaction or waiver of
all of the closing conditions set forth in the merger agreement, including the
approval and adoption of the merger agreement by CogenAmerica stockholders.

     The Calpine/NRG Agreement provides that the Board of Directors of the
surviving corporation (i.e., CogenAmerica following the merger) will consist of
no more than seven directors with one director being appointed by NRG. In
addition, the consent of NRG is

                                       48
<PAGE>   57

required for the surviving corporation or its subsidiaries to take certain
actions including, without limitation, actions relating to:

     - the issuance of securities;

     - the sale or disposition of subsidiaries or assets;

     - amendments to the certificate of incorporation or by-laws;

     - mergers or consolidations with third parties; and

     - certain agreements with affiliates.

     The Calpine/NRG Agreement prohibits Calpine and NRG from transferring their
respective shares of CogenAmerica common stock of the surviving corporation for
a period of three years after completion of the merger without the prior written
consent of the other stockholder, which consent cannot be unreasonably withheld
or delayed.

     Pursuant to the Calpine/NRG Agreement, NRG has granted Calpine an
irrevocable proxy with respect to all of the shares of CogenAmerica common stock
held by it (constituting 45.3% of the outstanding shares) to vote such shares in
favor of approval of the merger agreement and charter amendment at a duly
convened meeting of CogenAmerica's stockholders for such purpose. NRG has also
agreed that prior to the consummation of the merger, it shall not (i) solicit
third parties with respect to sale of shares of CogenAmerica common stock owned
by NRG and (ii) transfer the shares of CogenAmerica common stock owned by NRG
except as contemplated by the Calpine/ NRG Agreement.

     NRG and Calpine have agreed that prior to the consummation of the merger,
each party shall use reasonable efforts to take all actions and to do all things
necessary, proper or advisable in order to permit the consummation of the
merger. Calpine has agreed not to cause the merger agreement to be amended or
waive any of its rights thereunder in any way that would be materially adverse
to NRG without NRG's prior written consent.

     In the Calpine/NRG Agreement, NRG has granted Calpine with a right of first
refusal to acquire the shares of surviving corporation stock held by NRG.
Further, the Calpine/NRG Agreement provides that (i) Calpine can require that
NRG sell its shares in the event Calpine sells all or substantially all of its
shares in the surviving corporation (i.e., drag-along rights), and (ii) NRG can
require that its shares of surviving corporation stock be included in a
transaction in which Calpine sells any of its shares in the surviving
corporation to a third party (i.e., tag-along rights). The Calpine/NRG Agreement
also provides that Calpine shall have the right to acquire NRG's 20% interest in
CogenAmerica during the 365-day period commencing on the third anniversary of
the closing of the merger for the fair market value of the interest as
determined by an independent investment bank. Pursuant to the Calpine/NRG
Agreement, the surviving corporation is required to pay Calpine certain
management fees for management services to be provided by Calpine after
consummation of the merger through the fourth anniversary thereof.

                                       49
<PAGE>   58

                       PROPOSAL 2: THE CHARTER AMENDMENT

                        SUMMARY OF THE CHARTER AMENDMENT

     Article VII of CogenAmerica's Amended and Restated Certificate of
Incorporation places certain restrictions on the transfer of shares of
CogenAmerica common stock by any person that owns more than 5% of the
outstanding shares of CogenAmerica common stock until April 30, 2002. The
purpose of Article VII is to assure that the net operating loss carryforwards
("NOLs") of CogenAmerica will not be adversely affected by the transfer of
shares by such a holder. Article VII would require NRG to provide certain legal
opinions or that the CogenAmerica Board of Directors make certain determinations
as to the continued availability of the NOLs. Article VII provides an exception
for these requirements in the event the transfer is pursuant to a tender offer
for at least 66 2/3% of the outstanding shares of CogenAmerica common stock that
is followed by a merger in which the remaining stockholders receive the same
consideration as the stockholders that tendered their shares in the tender
offer. Since the merger does not technically fit within the express language of
Article VII and it may be difficult to comply the requirements of Article VII in
connection with the transfer of shares by NRG to Acquisition Sub immediately
prior to completion of the merger, the CogenAmerica Board of Directors has
approved and recommends that stockholders approve an amendment to Article VII
that will permit NRG to transfer shares of CogenAmerica common stock to
Acquisition Sub immediately prior to completion of the merger in order for NRG
to retain a 20% equity interest in CogenAmerica after the merger. A copy of the
charter amendment is attached as Appendix B to this proxy statement.

     THE COGENAMERICA BOARD OF DIRECTORS HAS UNANIMOUSLY APPROVED THE CHARTER
AMENDMENT, AND THE COGENAMERICA BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT
THE STOCKHOLDERS VOTE FOR APPROVAL OF THE CHARTER AMENDMENT.

                           MANAGEMENT OF COGENAMERICA

     Information concerning the management of CogenAmerica, the names, principal
occupations and employment history of the directors and executive officers of
CogenAmerica, is provided in CogenAmerica's Annual Report on Form 10-K for the
fiscal year ended December 31, 1998 that is incorporated by reference in this
proxy statement (SEC File No. 1-9208). All of the directors and executive
officers of CogenAmerica are citizens of the United States. The business
addresses of each director and executive officer of CogenAmerica is listed in
footnote 1 to the table under "Interests in Securities of CogenAmerica."

                     INTEREST IN SECURITIES OF COGENAMERICA

     The following table sets forth certain information with respect to the
beneficial ownership of the CogenAmerica common stock as of November   , 1999 by
(a) all persons known to CogenAmerica to own beneficially more than 5% of the
CogenAmerica common stock, (b) each executive officer and each director of
CogenAmerica, (c) all executive officers and directors of CogenAmerica as a
group, (d) the Employee Savings Plan (401(k) Plan) of CogenAmerica, (e) NRG and
Calpine, and (f) four officers or former officers of NRG who are directors of
CogenAmerica. Except as set forth below, no

                                       50
<PAGE>   59

other executive officer or director of Calpine, Acquisition Sub or NRG or its
ultimate parent, NSP, beneficially owns CogenAmerica common stock. As of
November   , 1999, there were 6,857,269 outstanding shares of CogenAmerica
common stock. Information presented with respect to options for purposes of this
proxy statement assumes that, as provided in the merger agreement on the date of
completion of the merger all options that are then exercisable, including the
acceleration of vesting as a result of the merger, will be converted into the
right to receive a cash amount equal to the excess, if any, of $25.00 over the
exercise price of the options multiplied by the number of shares of CogenAmerica
common stock so exercisable under the options. Value of stock options is the
aggregate cash amount payable to each owner of options upon completion of the
merger.

<TABLE>
<CAPTION>
                                                       SHARES BENEFICIALLY OWNED(1)
                                                ------------------------------------------
                                                   PERCENTAGE OF
                                                    OUTSTANDING
                                     NUMBER OF     SHARES AS OF      NUMBER OF    VALUE OF
          NAME AND ADDRESS            SHARES      NOVEMBER , 1999     OPTIONS     OPTIONS
          ----------------           ---------   -----------------   ---------   ----------
<S>                                 <C>         <C>                  <C>         <C>
NRG Energy, Inc.(2)...............  3,106,612                              --            --
1221 Nicollet Mall, Suite 700
Minneapolis, MN 55403-2445
Wexford Capital Partners II,
  L.P.(3).........................    443,976                              --            --
411 West Putnam Avenue
Greenwich, CT 06380
Calpine Corporation(2)............  3,106,612
50 West San Fernando Street
San Jose, CA 95113
David H. Peterson(4)(14)..........     31,000                          30,000    $  586,875
Julie A. Jorgensen(5).............    231,500                         230,000     3,163,750
Mark Liddell(6)...................     10,000                          10,000       126,250
Lawrence I. Littman(7)............     30,070                          30,000       586,875
Craig A. Mataczynski(8)(14).......     30,500                          30,000       586,875
Michael O'Sullivan................         --                              --
Charles J. Thayer(9)..............     40,000                          10,000       195,625
Ronald J. Will(10)(14)............     32,500                          30,000       586,875
Timothy P. Hunstad(11)............    112,500                         112,000     1,922,938
Thomas L. Osteraas(12)............     45,000                          45,000       604,687
Richard C. Stone(13)..............    120,000                         120,000     1,121,875
Directors and Executive Officers
  of CogenAmerica as a group......    683,070
</TABLE>

- ---------------
  *  Represents less than 1.0% of the outstanding shares of CogenAmerica common
     stock.

 (1) Under the rules of the SEC, a person is deemed to be a beneficial owner of
     a security if he or she has or shares the power to vote or to direct the
     voting of such security, or the power to dispose or to direct the
     disposition of such security. A person is also deemed to be a beneficial
     owner of any securities that such person has the right to acquire
     beneficial ownership of within 60 days as well as any securities

                                       51
<PAGE>   60
     owned by such person's spouse, children or relatives living in the same
     household. Accordingly, more than one person may be deemed to be a
     beneficial owner of the same securities. The address of Messrs. Peterson,
     Mataczynski, O'Sullivan and Will is 1221 Nicollet Mall, Suite 700,
     Minneapolis, Minnesota 55403-2445. The address of Ms. Jorgensen and Messrs.
     Hunstad, Osteraas and Stone is One Carlson Parkway, Suite 240, Minneapolis,
     Minnesota 55447-4454. The address of Mr. Liddell is 6307 Waterford
     Boulevard, Suite 100, Oklahoma City, Oklahoma 73118. The address of Mr.
     Littman is 1660 S A1, Apt. 212, Jupiter, Florida 33477-8449. The address of
     Mr. Thayer is 420 Isle of Capri Drive, Fort Lauderdale, Florida 33301-2438.

 (2) Calpine may be deemed to be the beneficial holder of securities owned by
     NRG as a result of entering into the Calpine/NRG Agreement. Under the terms
     of the Calpine/NRG Agreement, NRG has granted Calpine an irrevocable proxy
     with respect to all of the shares of CogenAmerica common stock held by NRG
     to vote those shares in favor of approval and adoption of the merger
     agreement and the charter amendment at a duly convened meeting of
     CogenAmerica's stockholders.

 (3) Includes 348,672 shares owned by Wexford Capital Partners II, LP and 95,304
     shares owned by Wexford Overseas Partners Fund I, LP. Through an investment
     management agreement, Wexford Management LLC, which manages the funds, has
     sole voting and investment power of the funds. This information is as of
     the date set forth in and based on the Schedule 13D filed May 8, 1997 and
     other information furnished to the Company by Wexford Management LLC.

 (4) Includes 30,000 shares issuable upon exercise of stock option at an
     exercise price of $5.4375 per share.

 (5) Represents 300 shares owned jointly with spouse and 1,200 beneficially
     owned by Ms. Jorgensen and includes 30,000 shares issuable upon exercise of
     stock option at an exercise price of $9.125 per share and 200,000 shares
     issuable upon exercise of stock option at an exercise price of $11.5625 per
     share, including 100,000 shares which will become vested and exercisable as
     a result of the completion of the merger.

 (6) Includes 10,000 shares issuable upon exercise of stock option at an
     exercise price of $12.375 per share which will become vested and
     exercisable as a result of the completion of the merger.

 (7) Includes 30,000 shares issuable upon exercise of stock option at an
     exercise price of $5.4375 per share.

 (8) Represents 500 shares beneficially owned by Mr. Mataczynski and includes
     30,000 shares issuable upon exercise of stock option at an exercise price
     of $5.4375 per share.

 (9) Represents 30,000 shares beneficially owned by Mr. Thayer and includes
     10,000 shares issuable upon exercise of stock option at an exercise price
     of $5.4375 per share.

(10) Represents 2,500 shares held jointly with spouse and includes 30,000 shares
     issuable upon exercise of stock option at an exercise price of $5.4375 per
     share.

(11) Represents 500 shares owned by Mr. Hunstad and includes 75,000 shares
     issuable upon exercise of stock option at an exercise price of $5.4375 per
     share, 17,000 shares issuable upon exercise of stock option at an exercise
     price of $14.00 per share, including 11,333 shares which will become vested
     and exercisable as a result of the merger, and 20,000 shares issuable upon
     exercise of stock option at an exercise price

                                       52
<PAGE>   61

     of $11.5625 per share, all of which will become vested and exercisable as a
     result of the completion of the merger.

(12) Includes 45,000 shares issuable upon exercise of stock options at an
     exercise price of $11.5625, all of which will become vested and exercisable
     as a result of the completion of the merger.

(13) Includes 100,000 shares issuable upon exercise of stock option at an
     exercise price of $16.46875 per share, including 86,667 shares which will
     become vested and exercisable as a result of the completion of the merger,
     and 20,000 shares issuable upon exercise of stock option at an exercise
     price of $11.5625 per share, all of which will become vested and
     exercisable as a result of the completion of the merger.

(14) Current NRG corporate policy prohibits NRG employees from receiving the
     economic benefit of options granted to them in their capacity as a director
     of CogenAmerica. The NRG employees who currently serve as directors of
     CogenAmerica and were previously granted stock options in their capacity as
     directors of CogenAmerica, have agreed to the cancellation of their stock
     options. The NRG employees who serve as directors of CogenAmerica will
     receive no cash payment for these options.

             CERTAIN TRANSACTIONS IN COMMON STOCK AND STOCK OPTIONS

     No transactions in CogenAmerica common stock or options have been effected
during the 60 days preceding the date of this proxy statement by CogenAmerica or
by the persons named under the caption "Interest in Securities of CogenAmerica"
except as provided in the Calpine/NRG Agreement described under the caption
"Summary of Calpine/NRG Agreement."

                          EXPENSES OF THE TRANSACTION

     The aggregate fees and expenses paid and estimated to be paid by
CogenAmerica in connection with the merger and related transactions are as
follows:

<TABLE>
<S>                                                   <C>
     Investment Banking Fee..............................  $ 3,418,500(1)
     Legal and Accounting................................      775,000
     Printing and Distribution...........................       50,000
     SEC and Regulatory Filings..........................       36,635
     Miscellaneous.......................................       19,865
                                                           -----------
          Total..........................................  $ 4,300,000
                                                           ===========
</TABLE>

- ---------------
(1) DLJ is also entitled to reimbursement of out-of-pocket expenses incurred in
    connection with its engagement (including reasonable fees and expenses of
    counsel).

                            INDEPENDENT ACCOUNTANTS

     PricewaterhouseCoopers LLP, independent certified public accountants, are
the independent accountants for CogenAmerica. A representative of
PricewaterhouseCoopers LLP, will be available at the special meeting to answer
questions.

                                       53
<PAGE>   62

                      WHERE YOU CAN FIND MORE INFORMATION

     CogenAmerica files annual, quarterly and special reports, proxy statements
and other information with the SEC. You may read and copy any such reports,
statements or other information at the SEC's public reference rooms in
Washington, DC, New York, New York and Chicago, Illinois. Please call the SEC at
1-800-SEC-0330 for further information on the public reference rooms.
CogenAmerica's SEC filings are also available to the public from commercial
document retrieval services and at the world wide web site maintained by the SEC
at Reports, proxy statements and other information concerning CogenAmerica also
may be inspected at the offices of the National Association of Securities
Dealers, Inc., 1735 K Street, N.W., Washington, DC 20006.

     The SEC allows CogenAmerica to incorporate by reference information into
this document, which means that CogenAmerica can disclose important information
to you by referring you to another document filed separately with the SEC. The
information incorporated by reference is deemed to be a part of this document,
except for any information superseded by information contained directly in this
document. This document incorporates by reference certain documents that
CogenAmerica has previously filed with the SEC. These documents contain
important business information about CogenAmerica and its financial condition.

     CogenAmerica may have sent to you some of the documents incorporated by
reference, but you can obtain any of them through CogenAmerica or the SEC or the
SECs World Wide Web site described above. Documents incorporated by reference
are available from CogenAmerica without charge, excluding all exhibits, unless
specifically incorporated by reference as an exhibit to this document.
Stockholders may obtain documents incorporated by reference in this document by
requesting them in writing or by telephone at the following address:

     Cogeneration Corporation of America
     One Carlson Parkway, Suite 240
     Minneapolis, Minnesota 55447-4454
     Attention: Thomas L. Osteraas
     Telephone: (612) 745-7900

     Calpine, Acquisition Sub and NRG have filed a Schedule 13E-3 with the SEC
with respect to the merger. The Schedule 13E-3, including any amendments and
exhibits filed or incorporated by reference as a part thereof, is available for
inspection or copying as set forth above. Statements contained in this proxy
statement or in any document incorporated herein by reference as to the contents
of any contract or other document referred to herein or therein are not
necessarily complete and in each instance reference is made to such contract or
other document filed as an exhibit to the Schedule 13E-3 or such other document,
and each such statement shall be deemed qualified in its entirely by such
reference.

     IF YOU WOULD LIKE TO REQUEST DOCUMENTS FROM COGENAMERICA, PLEASE DO SO AT
LEAST FIVE BUSINESS DAYS BEFORE THE DATE OF THE SPECIAL MEETING IN ORDER TO
RECEIVE TIMELY DELIVERY OF SUCH DOCUMENTS PRIOR TO THE SPECIAL MEETING.

     You should rely only on the information contained or incorporated by
reference in this document to vote your shares at the special meeting.
CogenAmerica has not authorized anyone to provide you with information that is
different from what is contained in this

                                       54
<PAGE>   63

document. This document is dated November   , 1999. You should not assume that
the information contained in this document is accurate as of any date other than
that date, and the mailing of this document to stockholders does not create any
implication to the contrary. This proxy statement does not constitute a
solicitation of a proxy in any jurisdiction where, or to or from any person to
whom, it is unlawful to make such proxy solicitation in such jurisdiction.

                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

     The following documents previously filed with the SEC by CogenAmerica (SEC
File No. 1-9208) are incorporated by reference in this proxy statement:

          (i) CogenAmerica's Annual Report on Form 10-K for the fiscal year
     ended December 31, 1998;

          (ii) CogenAmerica's Quarterly Report on Form 10-Q for the quarter
     ended March 31, 1999;

          (iii) CogenAmerica's Quarterly Report on Form 10-Q for the quarter
     ended June 30, 1999; and

          (iv) CogenAmerica's Current Report on Form 8-K filed on September 2,
     1999.

     All documents filed by CogenAmerica with the SEC pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act after the date of this document
and prior to the date of the special meeting will be deemed to be incorporated
by reference in this document. Information filed with the SEC in future
documents will automatically update and supersede the information in this
document.

                             STOCKHOLDER PROPOSALS

     If the merger is not completed for any reason, proposals of stockholders
intended to be presented at the 2000 Annual Meeting of Stockholders must be
received by Thomas L. Osteraas, Secretary and General Counsel, Cogeneration
Corporation of America, One Carlson Parkway, Suite 240, Minneapolis, Minnesota
55447-4454 on or prior to January 20, 2000 to be eligible for inclusion in
CogenAmerica's proxy statement and proxy card relating to that meeting.
CogenAmerica is not required to include in its proxy statement and proxy card
for the 2000 Annual Meeting any stockholder proposals which do not meet all of
the requirements then in effect for inclusion.

                                 OTHER MATTERS

     Management knows of no other business to be presented at the special
meeting. If other matters do properly come before the meeting, or any
adjournment or adjournments thereof, it is the intention of the persons named in
the proxy to vote on such matters according to their best judgment unless the
authority to do so is withheld in such proxy.
                                          By Order of the Board of Directors

                                          Julie A. Jorgensen
                                          President and Chief Executive Officer

                                       55
<PAGE>   64

                        CAUTIONARY STATEMENT CONCERNING
                          FORWARD-LOOKING INFORMATION

     THIS PROXY STATEMENT, THE SCHEDULE 13E-3 TRANSACTION STATEMENT FILED WITH
THE SECURITIES AND EXCHANGE COMMISSION AND OTHER STATEMENTS MADE FROM TIME TO
TIME BY COGENAMERICA, CALPINE, ACQUISITION SUB, NRG OR THEIR REPRESENTATIVES
CONTAIN FORWARD-LOOKING STATEMENTS. THOSE STATEMENTS INCLUDE STATEMENTS
REGARDING THE INTENT, BELIEF OR CURRENT EXPECTATIONS OF COGENAMERICA, CALPINE,
ACQUISITION SUB AND NRG AND MEMBERS OF THEIR RESPECTIVE MANAGEMENT TEAMS, AS
WELL AS THE ASSUMPTIONS ON WHICH SUCH STATEMENTS ARE BASED. SUCH FORWARD-LOOKING
STATEMENTS ARE NOT GUARANTEES OF FUTURE PERFORMANCE AND INVOLVE RISKS AND
UNCERTAINTIES. ACTUAL RESULTS MAY DIFFER MATERIALLY FROM THOSE CONTEMPLATED BY
SUCH FORWARD-LOOKING STATEMENTS. IMPORTANT FACTORS CURRENTLY KNOWN TO MANAGEMENT
OF COGENAMERICA, CALPINE, ACQUISITION SUB AND NRG THAT COULD CAUSE ACTUAL
RESULTS TO DIFFER MATERIALLY FROM THOSE IN FORWARD-LOOKING STATEMENTS INCLUDE,
BUT ARE NOT LIMITED TO, THE RISKS DETAILED IN THIS PROXY STATEMENT AND THE
SCHEDULE 13E-3 TRANSACTION STATEMENT, AND THOSE FACTORS SET FORTH FROM TIME TO
TIME IN REPORTS OF COGENAMERICA FILED WITH THE SECURITIES AND EXCHANGE
COMMISSION. THE PROTECTION FROM LIABILITY OF THE SAFE HARBOR FOR FORWARD-LOOKING
STATEMENTS CONTAINED IN THE PRIVATE SECURITIES REFORM ACT OF 1995 IS NOT
APPLICABLE TO THE INFORMATION CONTAINED IN THIS PROXY STATEMENT OR THE SCHEDULE
13E-3 TRANSACTION STATEMENT OR IN STATEMENTS INCORPORATED BY REFERENCE IN EITHER
DOCUMENT

                                       56
<PAGE>   65

                        APPENDIX TO THE PROXY STATEMENT

<TABLE>
<S>                                                             <C>
APPENDIX A -- Agreement and Plan of Merger..................    A-1
APPENDIX B -- Amendment to CogenAmerica Certificate of
  Incorporation.............................................    B-1
APPENDIX C -- Opinion of Donaldson Lufkin & Jenrette
  Securities Corporation....................................    C-1
APPENDIX D -- Text of Section 262 of the Delaware General
  Corporation Law...........................................    D-1
</TABLE>

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