SIERRA PACIFIC RESOURCES
424B5, 2000-05-08
ELECTRIC & OTHER SERVICES COMBINED
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<PAGE>
                                                Filed Pursuant to Rule 424(b)(5)
                                                      Registration No. 333-80149

P_R_O_S_P_E_C_T_U_S__S_U_P_P_L_E_M_E_N_T
(TO PROSPECTUS DATED MAY 3, 2000)
                                  $300,000,000
                                     [LOGO]

                             8 3/4% NOTES DUE 2005

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

    We will pay interest on the notes on May 15 and November 15 of each year,
beginning November 15, 2000. The notes will mature on May 15, 2005. We may
redeem some or all of the notes at any time before maturity at a make-whole
redemption price described more fully under the heading "Description of the
Notes--Optional Redemption" on page S-40 of this prospectus supplement.

    The notes are unsecured and will rank equally with all of our other
unsecured senior indebtedness. The notes will not be entitled to the benefit of
any sinking fund.

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

<TABLE>
<CAPTION>
                                                                PER NOTE             TOTAL
                                                                --------             -----
<S>                                                          <C>             <C>
    Public offering price (1)..............................     99.472%           $298,416,000
    Underwriting discount..................................       .6%             $  1,800,000
    Proceeds, before expenses, to Sierra Pacific
    Resources..............................................     98.872%           $296,616,000
</TABLE>

    (1) Plus accrued interest from May 9, 2000, if settlement occurs after that
       date

    Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus supplement or the accompanying prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

    The notes will be ready for delivery in book-entry form only through The
Depository Trust Company on or about May 9, 2000.

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

MERRILL LYNCH & CO.
                CREDIT SUISSE FIRST BOSTON
                                 SALOMON SMITH BARNEY

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

             The date of this prospectus supplement is May 5, 2000.
<PAGE>
                               TABLE OF CONTENTS
                             PROSPECTUS SUPPLEMENT

<TABLE>
<CAPTION>
                                                                PAGE
                                                              --------
<S>                                                           <C>
Special Note Regarding Forward-Looking Statements...........     S-4
The Offering................................................     S-5
Selected Information about Sierra Pacific Resources.........     S-6
Consolidated Ratios of Earnings to Fixed Charges and
  Preferred Dividends.......................................    S-13
Selected Pro Forma Consolidated Financial and Operating
  Data......................................................    S-13
Capitalization..............................................    S-14
Use of Proceeds.............................................    S-15
Recent Developments.........................................    S-15
Management's Discussion and Analysis of Results of
  Operations and Financial Condition........................    S-17
Description of the Notes....................................    S-39
United States Federal Tax Considerations....................    S-42
Underwriting................................................    S-47
Legal Matters...............................................    S-48
Experts.....................................................    S-48
Where You Can Find More Information.........................    S-48
Incorporation of Information We File with the SEC...........    S-49

                              PROSPECTUS
Sierra Pacific Resources....................................       1
The Trusts..................................................       1
Use of Proceeds.............................................       2
Consolidated Ratios of Earnings to Fixed Charges and
  Preferred Dividends.......................................       3
Description of the Debt Securities..........................       3
  General...................................................       3
  Terms of the Debt Securities..............................       4
  Consolidation, Merger or Sale.............................       5
  Modification of Indentures; Waiver........................       6
  Events of Default.........................................       6
  Remedies..................................................       7
    Acceleration of Maturity................................       7
    Waiver of Default.......................................       7
    Right to Direct Proceedings; Limitations................       7
    No Impairment of Right to Receive Payment...............       8
    Notice of Default.......................................       8
  Special Terms Relating to the Subordinated Debt Securities
    to be Held by Trusts....................................       8
    Subordination...........................................       8
    Redemption..............................................       8
    Option to Extend Interest Payment Date..................       9
    Restrictions on Certain Payments........................       9
    Option to Change Stated Maturity Date...................      10
  Special Terms Relating to the Senior Debt Securities......      11
    Limitations Upon Liens on Stock of Restricted
     Subsidiaries...........................................      11
    Limitations on the Issuance or Disposition of Stock of
     Restricted Subsidiaries................................      11
  Defeasance................................................      11
  Form, Registration, Transfer and Exchange.................      11
  Global Securities.........................................      12
</TABLE>

                                      S-2
<PAGE>

<TABLE>
<CAPTION>
                                                                PAGE
                                                              --------
<S>                                                           <C>
  Payment and Paying Agents.................................      12
  Governing Law.............................................      13
Description of the Preferred Securities of the Trusts.......      13
  General...................................................      13
  Distributions.............................................      14
  Mandatory Redemption......................................      14
  Trust Special Event Redemption or Distribution............      15
  Redemption Procedures.....................................      16
  Liquidation Distribution Upon Dissolution.................      17
  Subordination of the Common Securities....................      18
  Amendment of Declarations.................................      18
  Voting Rights.............................................      19
  Declaration Events of Default.............................      20
  Merger, Consolidation or Amalgamation of the Trusts.......      21
  Removal and Replacement of Trustees.......................      22
  Registrar, Transfer Agent, and Paying Agent...............      22
  Book-Entry Only Issuance--The Depository Trust Company....      22
    Description of the Global Certificates..................      22
    DTC Procedures..........................................      22
  Information Concerning the Property Trustee...............      24
  Governing Law.............................................      24
  Miscellaneous.............................................      25
Description of the Preferred Securities Guarantees..........      25
  General...................................................      25
  Events of Default.........................................      26
  Status of the Preferred Securities Guarantees;
    Subordination...........................................      26
  Amendments and Assignment.................................      26
  Termination of the Preferred Securities Guarantees........      27
  Information Concerning the Guarantee Trustee..............      27
  Governing Law.............................................      27
  The Expense Agreement.....................................      27
Relationship among Preferred Securities, Preferred
  Securities Guarantees and Subordinated Debt Securities
  held by the Trusts........................................      28
Plan of Distribution........................................      29
Where You Can Find More Information.........................      30
Incorporation of Information We File With the SEC...........      30
Legal Opinions..............................................      31
Experts.....................................................      31
</TABLE>

    You should rely only on the information contained in this prospectus
supplement and the accompanying prospectus. We have not, and the underwriters
have not, authorized any other person to provide you with different information.
If anyone provides you with different or inconsistent information, you should
not rely on it. We are not, and the underwriters are not, making an offer to
sell these securities in any jurisdiction where the offer or sale is not
permitted. You should assume that the information appearing in this prospectus
supplement and the accompanying prospectus is accurate only as of the date on
the front cover of this prospectus supplement. Our business, financial
condition, results of operations and prospects may have changed since that date.

                                      S-3
<PAGE>
               SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

    The information in this Prospectus Supplement, or in the accompanying
Prospectus or the documents incorporated by reference, includes forward-looking
statements within the meaning of the Private Securities Litigation Reform Act of
1995. These forward-looking statements relate to anticipated financial
performance, management's plans and objectives for future operations, business
prospects, outcome of regulatory proceedings, market conditions and other
matters. Words such as "anticipate," "believe," "estimate," "expect," "intend,"
"plan" and "objective" and other similar expressions identify those statements
that are forward-looking. These statements are based on management's beliefs and
assumptions and on information currently available to management. Actual results
could differ materially from those contemplated by the forward-looking
statements.

    In addition to any assumptions and other factors referred to specifically in
connection with such statements, factors that could cause our actual results to
differ materially from those contemplated in any forward-looking statement
include the following:

    - the pace and extent of the ongoing restructuring of the electric and gas
      industries in Nevada and California;

    - the outcome of regulatory and legislative proceedings and operational
      changes related to industry restructuring;

    - the amount our utility subsidiaries, Nevada Power Company and Sierra
      Pacific Power Company, are allowed to recover from customers for certain
      costs that prove to be uneconomic in the new competitive market;

    - regulatory delays or conditions imposed by regulatory bodies in approving
      the acquisition of Portland General Electric;

    - the outcome of ongoing and future regulatory proceedings;

    - management's ability to integrate the operations of Sierra Pacific
      Resources, Nevada Power Company, Sierra Pacific Power Company, and (after
      its acquisition) Portland General Electric and to implement and realize
      anticipated cost savings from the merger of Sierra Pacific Resources and
      Nevada Power Company and the acquisition of Portland General Electric;

    - the results of the contemplated sales by Nevada Power Company and Sierra
      Pacific Power Company of their Nevada-generating assets;

    - industrial, commercial and residential growth in the service territories
      of Nevada Power Company and Sierra Pacific Power Company;

    - fluctuations in electric, gas and other commodity prices and the ability
      to manage such fluctuations successfully;

    - changes in the capital markets and interest rates affecting the ability to
      finance capital requirements;

    - the loss of any significant customers;

    - the weather and other natural phenomena; and

    - changes in the business of major customers which may result in changes in
      the demand for services of Nevada Power Company, Sierra Pacific Power
      Company or (after its acquisition) Portland General Electric.

    Other factors and assumptions not identified above may also have been
involved in deriving these forward-looking statements, and the failure of those
other assumptions to be realized, as well as other factors, may also cause
actual results to differ materially from those projected. We assume no
obligation to update forward-looking statements to reflect actual results,
changes in assumptions or changes in other factors affecting forward-looking
statements.

                                      S-4
<PAGE>
                                  THE OFFERING

    The following is a brief summary of certain terms of this offering. For a
more complete description of the terms of the notes, see "Description of the
Notes" in this prospectus supplement.

<TABLE>
<S>                                      <C>
Issuer.................................  Sierra Pacific Resources.

Aggregate Principal Amount.............  $300,000,000.

Interest Rate..........................  8.75% per year.

Maturity Date..........................  May 15, 2005.

Interest Payment Dates.................  May 15 and November 15 of each year, beginning
                                         November 15, 2000.

Interest Calculations..................  Based on a 360-day year of twelve 30-day months.

Ranking................................  The senior notes will rank equally with all of our other
                                         unsecured and unsubordinated indebtedness.

Optional Redemption....................  The notes will be redeemable in whole or in part at our
                                         option at any time, on at least 30 days' but not more than
                                         60 days' prior written notice, at a price equal to the
                                         greater of (a) 100% of the principal amount of the notes
                                         being redeemed and (b) the sum of the present values of
                                         the remaining scheduled payments of principal and interest
                                         on the notes to be redeemed, discounted to the redemption
                                         date semi-annually (assuming a 360-day year consisting of
                                         twelve 30-day months) at a discount rate equal to the
                                         applicable Treasury Rate (as defined under "Description of
                                         the Notes--Optional Redemption") plus 25 basis points,
                                         plus accrued interest on the notes to the redemption date.
                                         See "Description of the Notes--Optional Redemption."

Sinking Fund...........................  None.

Form and Denominations.................  The notes initially will be issued in a fully registered
                                         book-entry form and will be represented by one or more
                                         registered global securities deposited with or on behalf
                                         of, and registered in the name of, a nominee of The
                                         Depository Trust Company. The notes will be issued in
                                         denominations of $1,000 and integral multiples thereof.
</TABLE>

                                      S-5
<PAGE>
              SELECTED INFORMATION ABOUT SIERRA PACIFIC RESOURCES

    THE FOLLOWING SELECTED INFORMATION HIGHLIGHTS CERTAIN IMPORTANT FACTS
REGARDING SIERRA PACIFIC RESOURCES AND ITS SUBSIDIARIES AND MAY NOT CONTAIN ALL
OF THE INFORMATION THAT IS IMPORTANT TO YOU. WE ENCOURAGE YOU TO READ
"MANAGEMENT'S DISCUSSION AND ANALYSIS OF RESULTS OF OPERATIONS AND FINANCIAL
CONDITION" STARTING ON PAGE S-17 OF THIS PROSPECTUS SUPPLEMENT AS WELL AS THE
DOCUMENTS REFERRED TO ON PAGE S-49 UNDER "INCORPORATION OF INFORMATION WE FILE
WITH THE SEC" WHICH CONTAIN MORE COMPLETE DESCRIPTIONS OF OUR COMPANY AND ITS
BUSINESS.

GENERAL

    Sierra Pacific Resources engages primarily in the energy business through
several subsidiaries. We completed a major merger with Nevada Power Company in
July 1999. Following the merger, our two largest subsidiaries are Nevada Power
Company and Sierra Pacific Power Company, both of which are regulated public
utilities. As discussed below, we have entered into an agreement to acquire
Portland General Electric Company. The diagram below shows the organizational
structure of our major companies after the Portland General Electric Company
acquisition is completed.

                                   [Diagram]

    Sierra Pacific Resources, through its public utility operating companies,
Sierra Pacific Power Company and Nevada Power Company, is engaged principally
in:

    - the generation, transmission, distribution and sale of electric energy;

    - the purchase, distribution, transportation and sale of natural gas; and

    - water distribution in selected markets.

    The principal markets of Sierra Pacific Resources utility operating
subsidiaries are currently located in Nevada and California and will include
Oregon upon successful completion of the Portland General Electric Company
acquisition. Sierra Pacific Resources is also involved in several non-regulated
and non-utility activities. The principal executive office of Sierra Pacific
Resources is P.O. Box 301500 (6100 Neil Road), Reno, Nevada 89520-3150, and the
telephone number is (775) 834-4011.

    In this prospectus supplement and the accompanying prospectus, "Sierra
Pacific," "Sierra Pacific Resources," "we," "us" and "our" refer specifically to
Sierra Pacific Resources, the holding company.

NEVADA POWER COMPANY

    Nevada Power Company is an operating public utility primarily engaged in the
distribution, transmission, generation, purchase and sale of electric energy in
Clark County in southern Nevada. The assets of Nevada Power Company represented
52% of the consolidated assets of Sierra Pacific Resources at December 31, 1999.
Nevada Power Company provides electricity to approximately 566,700 customers in
the communities of Las Vegas, North Las Vegas, Henderson, Searchlight, Laughlin
and adjoining areas. Service is also provided to Nellis Air Force Base and the
Department of Energy at Mercury and Jackass Flats at the Nevada Test Site.

    MARKET AND DISTRIBUTION SYSTEM

    All of Nevada Power Company's 1999 revenues, $977 million, were attributable
to its electricity operations. Nevada Power Company's total electric
megawatt-hour (MWh) sales have increased an average of 7.21% annually over the
past five years.

    Customer and sales growth in Nevada Power Company's service territory
continues to be among the fastest in the nation, and a significant part of the
growth in Nevada Power Company's electric sales has resulted from new
residential, industrial and gaming customers.

                                      S-6
<PAGE>
    The Las Vegas Portion of Nevada Power Company's service territory has
undergone significant customer growth recently as Las Vegas has become one of
the top resort destinations in the world. Ten of the world's largest resorts are
located in Las Vegas and the total number of hotel rooms available is
approximately 128,000; 13,000 of those rooms were added in 1999. In order to
meet the increased demand, McCarran International Airport has added
international carriers and increased flights into Las Vegas.

    In southern Nevada, summer peak loads are high relative to the winter peak,
as summer peak loads are driven by significant air conditioning demand. Nevada
Power Company's peak load increased an average of 8.14% annually over the past
five years, reaching 3,993 megawatts (MW) on July 1, 1999.

    Although resort activity is important to the region, efforts to diversify
southern Nevada's economy are continuing. In 1999, Nevada Power Company
contributed to these efforts by focusing a part of its recruitment and
attraction efforts on the plastics/polymers and metals fabrication industries.

    Nevada Power Company's electric customers grew at a compound annual growth
rate of 5.8% between 1994 and 1999 and contributed the following toward 1999 and
1998 megawatt-hour sales:

<TABLE>
<CAPTION>
                                                       MWH SALES
                                     ---------------------------------------------
                                             1999                    1998
                                     ---------------------   ---------------------
                                                    % OF                    % OF
CUSTOMERS                               MWH        TOTAL        MWH        TOTAL
- ---------                            ----------   --------   ----------   --------
<S>                                  <C>          <C>        <C>          <C>
Residential........................   6,138,436     37.9%     5,735,698     38.7%
Office.............................     875,716      5.4%       777,171      5.2%
Gaming, recreation, restaurants....   3,009,526     18.6%     2,604,906     17.6%
Wholesale..........................     829,551      5.1%       670,724      4.5%
Retail.............................     462,918      2.9%       405,833      2.7%
All other & unclassified...........   4,873,063     30.1%     4,638,646     31.3%
                                     ----------    ------    ----------    ------
      Total........................  16,189,210    100.0%    14,832,978    100.0%
</TABLE>

    CONSTRUCTION PROGRAM

    Of the $245.0 million allocated for construction in 1999, only
$224.0 million was actually spent. Internally generated funds provided 19.5% of
all of the funds for construction expenditures. Estimated construction
expenditures for 2000 are approximately $223.1 million.

    FACILITIES AND OPERATIONS

    Nevada Power Company committed to divest its generation facilities as a
condition of the PUCN's approval of its merger with Sierra Pacific Resources,
and Nevada Power Company has begun an auction process to sell these assets. The
auction process is anticipated to be completed by the first half of 2001,
however it may take longer to sell Nevada Power Company's interests in
jointly-owned power plants. Until such time, Nevada Power Company will continue
to provide energy through generation and purchased power to meet both summer and
winter peak loads.

    During 1999, Nevada Power Company generated more than half of its total
electric energy requirements in its own plants, as shown below:

                                      S-7
<PAGE>
EDGAR REPRESENTATION OF DATA POINTS USED IN PRINTED GRAPHIC

<TABLE>
<CAPTION>
    GAS/OIL      23%
<S>              <C>
Coal             34%
Purchased Power  43%
</TABLE>

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

* Does not include net sales of 872,302 MWh.

SIERRA PACIFIC POWER COMPANY

    Sierra Pacific Power Company is a public utility primarily engaged in the
distribution, transmission, generation, purchase and sale of electric energy. It
provides electricity to approximately 302,000 customers in a 50,000 square mile
service area including western, central and northeastern Nevada, including the
cities of Reno, Sparks, Carson City, Elko, and a portion of eastern California,
including the Lake Tahoe area.

    Sierra Pacific Power Company also provides natural gas service in Nevada to
approximately 110,000 customers and supplies water service to about 70,600
customers in the Reno/Sparks area and environs.

    In 1999, electric revenue accounted for 78.8% of Sierra Pacific Power
Company's total revenue, gas revenue accounted for 13.1% of total revenue and
water revenue accounted for 7.1% of total revenue.

    MARKET AND ELECTRIC DISTRIBUTION SYSTEM

    Sierra Pacific Power Company's 1999 electric revenues were $609 million. Its
total electric MWh sales have increased an average of 7.65% annually over the
past five years, reflecting the fact that its service area is among the fastest
growing in the nation. Sierra Pacific Power Company's growth in electric sales
has primarily resulted from new residential and mining and manufacturing
customers in northern Nevada.

    Sierra Pacific Power Company's electric customers grew at a compound annual
growth rate of 2.8% between 1994 and 1999 and contributed the following toward
1999 and 1998 megawatt-hour sales:

<TABLE>
<CAPTION>
                                                       MWH SALES
                                      --------------------------------------------
                                              1999                    1998
                                      ---------------------   --------------------
                                                     % OF                   % OF
CUSTOMERS                                MWH        TOTAL        MWH       TOTAL
- ---------                             ----------   --------   ---------   --------
<S>                                   <C>          <C>        <C>         <C>
Residential.........................   1,998,174     19.6%    1,987,562     20.4%
Commercial and Industrial:
  Mining............................   2,716,579     26.6%    2,648,957     27.1%
Offices/Schools/Government..........   1,128,189     11.1%    1,048,553     10.7%
  Resorts & Recreation..............     768,750      7.5%      760,848      7.8%
  Manufacturing/Warehouse...........     586,963      5.8%      738,972      7.6%
  Wholesale.........................   1,695,420     16.7%    1,443,652     14.6%
  All Other.........................   1,308,861     12.7%    1,134,675     11.8%
                                      ----------    ------    ---------    ------
      Total.........................  10,202,936    100.0%    9,763,219    100.0%
</TABLE>

                                      S-8
<PAGE>
    In Northern Nevada, electric system peaks typically occur in both the summer
and the winter. Summer peak loads result from air-conditioning, cooling
equipment and irrigation pumping, while winter peak loads are due to shorter
daylight hours, colder temperatures and ski resort demands. Sierra Pacific Power
Company's peak load increased an average of 5% annually over the past five
years, reaching 1,470 MW in July, 1999.

    According to the Nevada Mining Association statistics, Nevada leads the
nation in gold production, accounting for approximately 74% of all U.S.
production and 10% of world production, ranking it the third largest gold
producer in the world behind South Africa and Australia. A majority of Nevada's
gold mines are customers of Sierra Pacific Power Company. These reserves are
believed to be sufficient to continue production at current rates for the next
decade.

    Sierra Pacific Power Company's territory also has a variety of other mineral
producing mines, including silver, copper, lithium, mercury, barite, diatomite,
gypsum, and lime.

    Sierra Pacific Power Company has long-term power sales agreements with most
of our major mining customers with terms of at least five years. These mining
agreements secure over 223 MW of present and future mining load, or
approximately $74 million in annual revenues, which is 12.2% of the 1999
electric operating revenues.

    ELECTRIC FACILITIES AND OPERATIONS

    Sierra Pacific Power Company committed to divest its generation facilities
as a condition of the PUCN's approval of the merger of Nevada Power Company with
Sierra Pacific Resources. Sierra Pacific Power Company has begun an auction
process to sell these generation assets. The auction process is anticipated to
be completed by the first half of 2001, however it may take longer to sell
Sierra Pacific Power Company's interests in jointly owned power plants. Until
such time, Sierra Pacific will continue to provide energy through generation and
purchased power to meet both summer and winter peak loads.

    Sierra Pacific Power Company used diverse resources to meet its 1999
electric energy requirements, including gas and oil generation (28.4%), coal
generation (17.4%), hydro generation (0.4%), and purchased power (53.8%). The
company has no ownership interest in, nor does it operate, any nuclear
generating units. Sierra Pacific Power Company's decision to purchase spot
market energy is based on the economics of purchasing "as-available" energy when
it is less expensive than Sierra Pacific Power Company's own generation. At the
time of the 1999 system peak, Sierra Pacific Power Company had purchased firm
capacity under long-term contracts with other utilities and qualifying
facilities (QFs) equal to 17% of total peak hour capacity. In 1999, most of
Sierra Pacific Power Company's non-utility generation came from QFs, except for
14,951 MWh which came from two small power producers.

EDGAR REPRESENTATION OF DATA POINTS USED IN PRINTED GRAPHIC

<TABLE>
<CAPTION>
    GAS/OIL      28.40%
<S>              <C>
Coal             17.40%
Hydro             0.40%
Purchased Power  53.80%
</TABLE>

                                      S-9
<PAGE>
    NATURAL GAS BUSINESS

    Sierra Pacific Power Company's natural gas business is a local distribution
company ("LDC") in the Reno/Sparks metropolitan area with 111,843 customers and
$100.2 million in 1999 operating revenues. The overall natural gas customer
growth rate was 4.3% for 1999. As of December 31, 1999, Sierra Pacific Power
Company owned and operated 1,439 miles of three-inch equivalent natural gas
distribution pipe.

    WATER BUSINESS

    Sierra Pacific Power Company's water distribution business, with 70,600
customers and $54.3 million in 1999 operating revenues, produced 24.97 billion
gallons in 1999. Sierra Pacific Power Company derives its water supply from both
surface and groundwater sources. Sierra Pacific Power Company's groundwater
comes from 25 supply wells located around the Reno/Sparks area, and its surface
water is drawn from the Truckee River which originates at Lake Tahoe.

    CONSTRUCTION PROGRAM FOR ELECTRIC, GAS AND WATER BUSINESSES

    Gross construction expenditures for Sierra Pacific Power Company's electric,
gas and water businesses, including AFUDC and contributions in aid of
construction, were $142.3 million in 1999 and $820.8 million for the period 1995
through 1999. Internally generated funds provided 35% of all construction
expenditures in 1999. Estimated construction expenditures are $137.7 million for
2000 and $679.8 million for the period 2001-2004.

    The most significant of Sierra Pacific Power Company's current construction
projects is the Falcon Transmission Project, a 345kV transmission line within
Northern Nevada. Total project costs are estimated at $98.2 million. The
currently projected in-service date for the Falcon Transmission Project is
June 2003.

GENERAL REGULATION

    Nevada Power Company and Sierra Pacific Power Company's electric businesses
are subject to regulation by the PUCN, the Federal Energy Regulatory Commission
("FERC") and by environmental authorities in the states in which they operate.
Sierra Pacific Power Company's electric business in California is subject to
regulation by the California Public Utility Commission. In addition, Sierra
Pacific Power Company's natural gas and water businesses are subject to
regulation by the PUCN. As a result of regulation, many of the fundamental
business decisions of Nevada Power Company and Sierra Pacific Power Company, as
well as the rate of return we are permitted to earn on our utility assets, are
subject to the approval of governmental agencies.

    Following completion of the acquisition of PGE, Sierra Pacific Resources
will register as a public utility holding company under the federal Public
Utility Holding Company Act.

    Sierra Pacific Power Company and Nevada Power Company continue to prepare
for a more competitive environment and have actively participated in regulatory
reform deliberations in Nevada. The Nevada Legislature mandated retail access to
alternative electric suppliers to commence March 1, 2000, a deadline which has
since been extended indefinitely by the Governor of Nevada. Once retail access
begins, Sierra Pacific Power Company and Nevada Power Company will retain the
responsibility to supply electricity to customers as the "provider of last
resort". We expect, assuming no regulatory relief, that Sierra Pacific Power
Company and Nevada Power Company will exit their positions as the providers of
last resort as quickly as possible. We also expect that, if current legislation
and regulation do not change, Sierra Pacific Power Company and Nevada Power
Company will exit other services, including metering, billing and customer
service functions. As discussed under "Recent Developments--Material
Litigation", our two utility subsidiaries have filed a lawsuit challenging the
constitutionality of

                                      S-10
<PAGE>
the Nevada electric restructuring legislation. We cannot predict the outcome of
this litigation at this time.

NON-UTILITY SUBSIDIARIES

    In addition to the two utility subsidiaries, we have several other
subsidiaries that are described below.

    Tuscarora Gas Pipeline Company ("TGPC") is a partner in a joint venture with
TransCanada that developed, constructed and operates a natural gas pipeline
serving the gas market in the Reno area and (certain) northeastern California
markets. As an interstate pipeline, TGTC provides only transportation service.
Sierra Pacific Power Company was the largest customer of TGTC during 1999,
contributing 95% of revenues.

    e.three provides energy-related services and other business solutions in
commercial and industrial markets (on a regional basis). In 1998, e.three and
Nevada Electric Investment Company ("NEICO"), a wholly-owned subsidiary of
Nevada Power Company, formed e.three Custom Energy Solutions, LLC to sell
energy-related performance contracts and similar energy services to commercial
and industrial customers in southern Nevada. In 1999, e.three Custom Energy
Solutions, LLC began developing a chilled water-cooling plant in the downtown
area of Las Vegas which will supply the indoor air-cooling requirements for a
number of businesses in its immediate vicinity. The plant is expected to be
operational in the third quarter of 2000.

    Sierra Pacific Communications ("SPC") was created to examine and pursue
telecommunications opportunities that leverage existing skills in installing and
deploying pipe and wire infrastructure. SPC presently has fiber optic assets
deployed in the cities of Reno and Las Vegas. We believe that the expanding
telecommunications market in these areas should provide opportunities to expand
this fiber base and other profitable opportunities.

    Sierra Pacific Energy ("SPE") was formed to market a package of technology
and energy-related products and services in Nevada. SPE filed an application
with the PUCN to be licensed as an Alternative Seller of Electricity in the
State of Nevada. Except for its interest in the Aladdin project discussed below,
SPE has withdrawn its application with the PUCN to be licensed as an Alternative
Seller of Electricity in the State of Nevada and is dissolving its retail energy
marketing efforts. SPE will retain its interest in the Northwind Aladdin LLC (a
limited liability company owned by NEICO & UTT Nevada, Inc., an affiliate of
Unicom Thermal Technologies, Inc.) to own, construct and maintain a chilled
water, hot water, and emergency electric power facility for the Aladdin project
in Las Vegas, Nevada.

    Lands of Sierra ("LOS") was organized in 1964 to develop and manage Sierra
Pacific Power Company's non-utility property in Nevada and California. These
properties previously included retail, industrial, office and residential sites,
timberland, and other properties. Remaining properties include land in Nevada
and California. Because we have decided to focus on our core energy business,
LOS continues to sell its remaining properties.

    Information regarding the financial performance of these subsidiaries can be
found in "Management's Discussion and Analysis of Results of Operations and
Financial Condition" starting on page S-17 of this prospectus supplement.

                                      S-11
<PAGE>
    CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES AND PREFERRED DIVIDENDS

    The following table shows our consolidated ratios of earnings to fixed
charges and preferred dividends. The ratios shown in the table are both the
historical ratios and the pro forma combined ratio showing the effect of the
merger between Sierra Pacific Resources and Nevada Power Company. As a result of
the merger between Sierra Pacific Resources and Nevada Power Company, which has
been treated for accounting purposes as a reverse acquisition with Nevada Power
Company being the acquiror, the historical ratios are those of Nevada Power
Company. The pro forma ratio assumes that the merger occurred at the beginning
of the applicable period.

<TABLE>
<CAPTION>
                                                1999                    YEAR ENDED DECEMBER 31,
                                             (COMBINED    ----------------------------------------------------
                                             PRO FORMA)     1999       1998       1997       1996       1995
                                             ----------   --------   --------   --------   --------   --------
<S>                                          <C>          <C>        <C>        <C>        <C>        <C>
Consolidated ratio of earnings
  to fixed charges and preferred
  dividends................................     1.68        1.62       2.48       2.70       2.64       2.60
</TABLE>

    For the purpose of calculating the consolidated ratio of earnings to fixed
charges and preferred dividends, "fixed charges" represent the aggregate of
interest charges on short-term and long-term debt and distributions on preferred
securities of consolidated subsidiaries, allowance for borrowed funds used
during construction ("AFUDC") and capitalized interest, the interest portion of
rental expense deemed to be attributable to interest, and the pre-tax preference
security dividend requirements of consolidated subsidiaries. "Earnings"
represent the aggregate of income before obligated mandatorily redeemable
preferred securities, income taxes, and fixed charges, less AFUDC and
capitalized interest, and pre-tax preference security dividend requirements of
consolidated subsidiaries.

          SELECTED PRO FORMA CONSOLIDATED FINANCIAL AND OPERATING DATA
                 (IN MILLIONS EXCEPT RATIOS AND PER SHARE DATA)

    The following table shows pro forma unaudited financial information for
Sierra Pacific Resources on a consolidated basis, giving effect to the merger
between Sierra Pacific Resources and Nevada Power Company as if it had occurred
at the beginning of all periods. The pro forma information presented below is
not necessarily indicative of the results that would have occurred or that will
occur in the future.

    You should read the following table along with our Consolidated Financial
Statements and Notes contained in our Annual Report on Form 10-K for the year
ended December 31, 1999, which is incorporated by reference into this prospectus
supplement. You should also refer to "Management's Discussion and Analysis of
Financial Condition and Results of Operations" beginning on page S-17 of this
prospectus supplement.

<TABLE>
<CAPTION>
                                             TWELVE MONTHS ENDED DECEMBER 31,
                                           ------------------------------------
                                              1999         1998         1997
                                           ----------   ----------   ----------
                                            (DOLLARS AND SHARES IN THOUSANDS)
<S>                                        <C>          <C>          <C>
Operating Revenue........................  $1,756,235   $1,615,523   $1,462,391
Operating Income.........................  $  253,785   $  281,759   $  266,185
Net Income...............................  $   82,449   $  141,355   $  138,022
Long-Term Debt and Redeemable Preferred
  Securities.............................  $1,793,999   $1,804,527   $1,709,772
Total Assets as of December 31...........  $5,247,606   $4,979,631   $4,605,713
</TABLE>

                                      S-13
<PAGE>
                                 CAPITALIZATION

    The following table shows the capitalization of Sierra Pacific Resources and
its consolidated subsidiaries as of December 31, 1999 and as adjusted to give
effect to the sale of $300 million of notes, as well as the sale on April 20,
2000 of $300 million of floating rate notes and the use of the proceeds from
those sales. The majority of the net proceeds from the sale of the notes will be
used to retire short-term debt. The following information should be read
together with the financial statements and notes thereto and "Management's
Discussion and Analysis of Financial Condition and Results of Operations"
beginning on page S-17 of this prospectus supplement.

<TABLE>
<CAPTION>
                                                                            AS OF DECEMBER 31, 1999
                                              -----------------------------------------------------------------------------------
                                                ACTUAL           %                 AS ADJUSTED                        %
                                              ----------      --------      --------------------------      ---------------------
                                                                                (IN THOUSANDS)
<S>                                           <C>             <C>           <C>                             <C>
SHORT-TERM DEBT (INCLUDING CURRENT
  MATURITIES OF LONG-TERM DEBT AND
  PREFERRED STOCK):.....................      $  957,688        22.4%       $                  357,688                        8.4%

LONG-TERM DEBT:
First Mortgage Bonds....................         898,751        21.0%                          898,751                       21.0%
Industrial development revenue bonds....         358,035         8.4%                          358,035                        8.4%
Pollution control revenue bonds.........          73,300         1.7%                           73,300                        1.7%
Unsecured Notes.........................         130,000         3.0%                          430,000                       10.0%
  8.75% Notes due 2005..................                                                       300,000                        7.0%
Obligation under capital leases.........          87,007         2.0%                           87,007                        2.0%
Current maturities and sinking fund
  requirements..........................         (89,842)       -2.1%                          (89,842)                      -2.1%
Variable rate note--Water facilities....          80,000         1.9%                           80,000                        1.9%
Other, excluding current portion........          19,376         0.5%                           19,376                        0.5%
                                              ----------       -----        --------------------------      ---------------------
    Total Long-Term Debt................       1,556,627        36.4%                        2,156,627                       50.4%

PREFERRED SECURITIES OF SUBSIDIARIES:
NVP obligated Mandatorily Redeemable
  Preferred Securities of Company's
  NVP's Subsidiary Trust, NVP Capital I,
  holding solely $122.6 million
  principal amount of 8.2% Junior
  Subordinated Debentures of NVP, due
  2037..................................         118,872         2.8%                          118,872                        2.8%
NVP Capital III, holding solely $72.2
  million principal amount of 7.75%
  Junior Subordinated Debentures of NVP,
  due 2038..............................          70,000         1.6%                           70,000                        1.6%
SPPC obligated Mandatorily Redeemable
  Preferred Securities of SPPC's
  Subsidiary Trust, SPPC Capital I,
  holding solely $50 million principal
  amount of 8.60% Junior Subordinated
  Debentures of SPPC, due 2036..........          48,500         1.1%                           48,500                        1.1%
                                              ----------       -----        --------------------------      ---------------------
    Total Preferred Securities..........         237,372         5.5%                          237,372                        5.5%

SHAREHOLDERS' EQUITY:
Preferred Stock of Subsidiaries:
  Class A Series 1; $1.95 dividend......          50,000         1.2%                           50,000                        1.2%
Common Shareholders' Equity:............       1,477,129        34.5%                        1,477,129                       34.5%
                                              ----------       -----        --------------------------      ---------------------
    Total Shareholders' Equity..........       1,527,129        35.7%                        1,527,129                       35.7%
                                              ----------       -----        --------------------------      ---------------------
      Total Capitalization..............      $4,278,816         100%       $                4,278,816                        100%
                                              ==========       =====        ==========================      =====================
</TABLE>

                                      S-14
<PAGE>
                                USE OF PROCEEDS

    We intend to use most of the net proceeds from the sale of the notes to
retire short-term debt which we borrowed to provide temporary funding for the
cash portion of the merger consideration in the merger between Sierra Pacific
Resources and Nevada Power Company. As of March 31, 2000, there was
$493.2 million of total short-term debt outstanding, $460 million of which
related to the merger, and the weighted average interest rate on short-term debt
during the first quarter of 2000 was 6.35%. We intend to use any remaining net
proceeds from the sale of the notes for general corporate purposes, which may
include financing the activities of our subsidiaries, refinancing our existing
borrowings and financing acquisitions. Until we use the remaining net proceeds
from the sale of the notes for general corporate purposes, we will invest the
net proceeds in temporary investments.

                              RECENT DEVELOPMENTS

    AGREEMENT TO ACQUIRE PORTLAND GENERAL ELECTRIC COMPANY

    On November 8, 1999, we announced that we had entered into a purchase and
sale agreement with Enron Corporation ("Enron") for Enron's wholly owned
electric utility subsidiary, Portland General Electric Company ("PGE"). PGE is
an electric utility serving more than 700,000 retail customers in northwest
Oregon. PGE will become a wholly-owned subsidiary of Sierra Pacific Resources.
Under terms of the agreement, Enron will sell PGE to us for $2.1 billion, which
will consist of $2.02 billion in cash and our assumption of Enron's
approximately $80 million merger payment obligation. In addition, $1.0 billion
in PGE debt and preferred stock will be reflected in our consolidated financial
statements. At closing, the transaction is expected to be financed primarily
through a bank loan or other form of debt. Ultimately, the transaction is
expected to be financed through approximately $750 million of proceeds from the
sale of generation assets of our two Nevada subsidiaries and the issuance by us
of debt and equity securities. Immediately after the acquisition of PGE, we
expect that our consolidated common equity will be approximately 23 percent of
total consolidated capitalization. During the two years following the
acquisition, however, we intend to increase consolidated common equity to
approximately 29 percent by paying down a portion of the acquisition debt with
proceeds from the sale of the electric generation assets of Nevada Power Company
and Sierra Pacific Power Company, the sale of additional common stock, and
increased retained earnings from the combined operations of the three utility
subsidiaries. Our ability to increase our common equity will depend upon, among
other things, market conditions and the results of operations of these
subsidiaries. See "Capitalization" on page S-14.

    The proposed transaction is subject to customary closing conditions, such as
the receipt of all necessary governmental approvals, including from the Federal
Energy Regulatory Commission ("FERC"), the Securities and Exchange Commission
("SEC"), the Oregon Public Utility Commission ("OPUC") and the Nuclear
Regulatory Commission. Also, we intend to register with the SEC as a public
utility holding company under the Public Utility Holding Company Act. The Public
Utilities Commission of Nevada ("PUCN") has waived its jurisdiction over Sierra
Pacific Resources' registration as a public utility holding company. We have
completed our filings with the Federal Energy Regulatory Commission, the
Department of Justice, the OPUC and the SEC. Approvals are expected to be
received by the second half of 2000 with a closing to follow shortly thereafter.

    RECENT DECISIONS IN NEVADA POWER COMPANY DEFERRED ENERGY CASE

    In 1999, the Nevada Legislature passed Senate Bill 438 ("SB 438") which
amended earlier restructuring legislation and, with one exception, froze for
three years the rates for Nevada Power Company at levels in effect on July 1,
1999. The legislation, however, mandated that the PUCN modify those rates to
reflect the outcomes of deferred accounting cases filed by Nevada Power Company
prior

                                      S-15
<PAGE>
to October 1, 1999. Nevada Power filed its annual deferred energy case on July
15, 1999, covering the period from June 1, 1998 through May 31, 1999. This
filing requested:

    - an increase in ongoing charges for fuel and purchased power to reflect
      increased costs during the applicable test period,

    - an increase in ongoing charges for fuel and purchased power to reflect the
      cost of purchased energy which was being imputed as "capacity" under a
      previous PUCN order,

    - an increase to recover accumulated deferred balances for fuel and
      purchased power, and

    - an increase to recover accumulated deferred "capacity" balances.

    In accordance with SB 438, on September 30, 1999, Nevada Power filed an
amendment to its deferred energy filing covering charges through August 31,
1999. In the amended filing, Nevada Power updated the earlier calculations of
ongoing fuel and purchased power costs so as to reflect the most recent
12 months historical data and updated the two categories of deferred balances to
reflect deferrals through August 31, 1999.

    On February 4, 2000 the PUCN issued an order that rejected the September 30
amendment. In addition, on March 28, 2000 the PUCN issued a decision on the
original deferred energy filing which:

    - confirmed the dismissal of the September 30th filing,

    - disallowed recovery of substantially all of the imputed capacity
      previously deferred,

    - stopped all purchased fuel and energy deferrals retroactive to May 31,
      1999, and

    - prohibited the recovery of any ongoing cost of imputed capacity deferrals.

    The PUCN decision had both an immediate and an ongoing financial impact on
Nevada Power Company. The immediate impact was that Nevada Power Company
recognized a reserve for previously deferred energy and imputed capacity costs
of $80 million in 1999. The ongoing impact results from the fact the decision
reduced Nevada Power Company's request for ongoing rate increases by between 85
and 90 percent, just as the company is entering the three-year rate freeze
imposed by SB 438. We estimate that the resulting reduction in Nevada Power
Company's revenue will equal approximately $30 million over each of the next
three years. Nevada Power Company has appealed the decisions, as discussed below
under "Material Litigation".

    MATERIAL LITIGATION

    On March 28, 2000, Sierra Pacific Resources, Nevada Power Company and Sierra
Pacific Power Company filed a lawsuit in Federal District Court in Nevada asking
the court to declare certain aspects of the Nevada laws that created the
framework for a deregulated electric market in Nevada unconstitutional. These
laws, which are described in more detail later in this prospectus supplement
under "Management's Discussion and Analysis of Results of Operations and
Financial Condition" starting on page S-17, require that competitive services in
the electric power industry be available for Nevada customers beginning on
March 1, 2000, unless otherwise ordered by the Governor of Nevada. The Governor
has deferred the effective date of these laws, but only for so long as may be
necessary to make a transition to a deregulated market for electric services.
The lawsuit we filed alleges that the restructuring laws fail to provide an
adequate mechanism for the recovery by our utility subsidiaries of the
substantial costs incurred by them to assure reliable electric power supplies to
Nevada customers in the historically regulated market. Specifically, the lawsuit
states that the federal Public Utility Regulatory Policies Act requires the
utilities to purchase power from certain non-utility generators but that the
Nevada restructuring laws are being carried out so as to prevent the utilities
from recovering sufficient revenues from customers to compensate the companies
for all of these purchased power costs. Therefore, the lawsuit alleges that
Nevada's restructuring laws are preempted by the federal

                                      S-16
<PAGE>
Public Utility Regulatory Policies Act and the Federal Power Act and that they
violate the Contract Clause and the Fifth and Fourteenth Amendments to the U.S.
Constitution. The lawsuit requests that the court stay the effectiveness of the
Nevada restructuring laws until the PUCN adopts implementing regulations that
protect the utilities' rights under federal law. We are not able at this time to
predict how long it will take for this lawsuit to be resolved and nor can we
predict its outcome.

    In response to the PUCN decisions described above under "Recent Decisions in
Nevada Power Company Deferred Energy Case", Nevada Power Company filed a lawsuit
against the PUCN on March 30, 2000 in the First Judicial District of Nevada in
Carson City. The lawsuit alleges fourteen causes of action against the PUCN and
requests that the court:

    - set aside the PUCN's March 28, 2000 order,

    - reinstate Nevada Power Company's September 30th filing, and

    - enter an order allowing Nevada Power Company to recover deferrals of
      imputed capacity through March 28, 2000 and implement ongoing rates for
      fuel and purchased power that reflect the costs of purchased energy.

    We are not able at this time to predict how long it will take for this
lawsuit to be resolved nor can we predict its outcome.

                      MANAGEMENT'S DISCUSSION AND ANALYSIS
                OF RESULTS OF OPERATIONS AND FINANCIAL CONDITION

    The merger between Sierra Pacific Resources ("SPR") and Nevada Power Company
("NVP") was accounted for as a reverse purchase under generally accepted
accounting principles, with NVP considered the acquiring entity, even though SPR
survives and is the legal parent of NVP. For accounting purposes, the merger was
deemed to have occurred on August 1, 1999. As a result of this reverse purchase
accounting treatment: (i) the historical financial statements of SPR for periods
prior to the date of the merger are no longer the financial statements of SPR,
and therefore, are no longer presented; (ii) the historical financial statements
of SPR for periods prior to the date of the merger are those of NVP;
(iii) based on a merger date of August 1, 1999, the Consolidated Statements of
Income for the twelve months ended December 31, 1999 include five months (August
through December 1999) of operating activity for SPR and its subsidiaries other
than NVP. The same statements include the operating results of NVP for the
entire periods presented.

RESULTS OF OPERATIONS OF EACH SUBSIDIARY

    SIERRA PACIFIC RESOURCES (HOLDING COMPANY)

    The consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of the holding
company for the five month period ended December 31, 1999, based on a merger
date of August 1, 1999. The holding company operating results included
approximately $11.5 million of interest costs that resulted from the merger
financing.

    TUSCARORA GAS PIPELINE COMPANY

    The Consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of Tuscarora Gas
Pipeline Company ("TGPC"), a wholly-owned subsidiary of SPR, for the five month
period ended December 31, 1999 based on a merger date of August 1, 1999 for
accounting purposes. TGPC contributed $711 thousand in net income for the five
months ended December 31, 1999. TGPC contributed $1.8 million in net income for
the twelve months ended December 31, 1999.

                                      S-17
<PAGE>
    E.THREE

    The Consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of e.three, a
wholly-owned subsidiary of SPR, for the five month period ended December 31,
1999 based on a merger date of August 1, 1999 for accounting purposes. e.three
incurred net losses of $381 thousand for the five months ended December 31,
1999. e.three incurred net losses of $788 thousand for the twelve months ended
December 31, 1999.

    SIERRA PACIFIC ENERGY COMPANY

    The Consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of Sierra Pacific
Energy Company ("SPE"), a wholly-owned subsidiary of the Company, for the five
month period ended December 31, 1999 based on a merger date of August 1, 1999
for accounting purposes. SPE incurred net losses of $2.2 million for the five
months ended December 31, 1999. SPE incurred net losses of $3.6 million for the
twelve months ended December 31, 1999.

    SIERRA PACIFIC COMMUNICATIONS

    The Consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of Sierra Pacific
Communications ("SPC"), a wholly-owned subsidiary of SPR, for the five month
period ended December 31, 1999 based on a merger date of August 1, 1999 for
accounting purposes. SPC incurred net losses of $62 thousand for the five months
ended December 31, 1999. SPC incurred net losses of $75 thousand for the twelve
months ended December 31, 1999.

    LANDS OF SIERRA

    The Consolidated Statements of Income of Sierra Pacific Resources for the
year ended December 31, 1999 include the operating results of Lands of Sierra
("LOS"), a wholly-owned subsidiary of SPR, for the five month period ended
December 31, 1999 based on a merger date of August 1, 1999 for accounting
purposes. LOS contributed $816 thousand in net income for the five months ended
December 31, 1999. LOS contributed $810 thousand in net income for the twelve
months ended December 31, 1999.

    NEVADA POWER COMPANY

    Based on a merger date of August 1, 1999, the Consolidated Statements of
Income for the twelve months ended December 31, 1999 include five months (August
through December 1999) operating activity for the Company and its subsidiaries
other than NVP. The same statements include the operating results of NVP for all
of 1999 and all prior year periods presented.

    As a result, the following Consolidating Statements of Income illustrate the
operating results of SPR's principal subsidiaries (NVP and Sierra Pacific Power
Company ("SPPC")) and the combined results of all Other operations. The results
of operations discussion that follows is based on the NVP operating results
included in these statements. Following the discussion of NVP's operating
results is a discussion of SPPC's operating results. The operating results of
the other subsidiaries have already been discussed in this section.

                                      S-18
<PAGE>
          SIERRA PACIFIC RESOURCES CONSOLIDATING STATEMENTS OF INCOME

<TABLE>
<CAPTION>
                                                     YEAR ENDED DECEMBER 31, 1999                    YEARS ENDED DECEMBER 31,
                                       ---------------------------------------------------------   -----------------------------
                                                          5 MONTHS
                                         12 MONTHS     SIERRA PACIFIC   5 MONTHS    CONSOLIDATED       1998            1997
                                       NEVADA POWER        POWER          OTHER        TOTAL       NEVADA POWER    NEVADA POWER
                                       -------------   --------------   ---------   ------------   -------------   -------------
                                                                        (DOLLARS IN THOUSANDS)
<S>                                    <C>             <C>              <C>         <C>            <C>             <C>
OPERATING REVENUES:
  Electric...........................    $977,262         $259,440      $     --     1,236,702       $873,682        $799,148
  Gas................................          --           38,958            --        38,958             --              --
  Water..............................          --           24,339            --        24,339             --              --
  Other..............................          --               --         9,132         9,132             --              --
                                         --------         --------      --------     ---------       --------        --------
                                          977,262          322,737         9,132     1,309,131        873,682         799,148
                                         --------         --------      --------     ---------       --------        --------
OPERATING EXPENSES:
  Operation:
    Purchased power..................     293,600           79,856            --       373,456        283,838         277,644
    Fuel for power generation........     154,546           51,584            --       206,130        149,804         138,956
    Gas purchased for resale.........          --           27,262            --        27,262             --              --
    Deferral of energy costs-net.....      97,238               --            --        97,238        (29,680)        (60,400)
    Other............................     141,041           51,038        11,389       203,468        134,652         122,811
  Maintenance........................      50,805            9,579            --        60,384         49,082          52,126
  Depreciation and amortization......      80,644           32,349           243       113,236         73,562          66,273
  Taxes:.............................                                         --            --
    Income taxes.....................      19,943           11,390        (5,247)       26,086         42,949          43,478
    Other than income................      22,462            8,161            90        30,713         22,198          21,064
                                         --------         --------      --------     ---------       --------        --------
                                          860,279          271,219         6,475     1,137,973        726,405         661,952
                                         --------         --------      --------     ---------       --------        --------
OPERATING INCOME.....................     116,983           51,518         2,657       171,158        147,277         137,196
                                         --------         --------      --------     ---------       --------        --------
OTHER INCOME:
  Allowance for other funds used
    during construction..............       3,713           (1,339)           --         2,374          8,944           8,760
  Other income--net..................      (1,824)          (1,044)          352        (2,516)        (4,602)         (5,741)
                                         --------         --------      --------     ---------       --------        --------
                                            1,889           (2,383)          352          (142)         4,342           3,019
                                         --------         --------      --------     ---------       --------        --------
      Total Income...................     118,872           49,135        (5,391)      171,016        151,619         140,215
                                         --------         --------      --------     ---------       --------        --------
INTEREST CHARGES:
  Long-term debt.....................      64,454           16,978           299        81,731         56,995          50,791
  Other..............................       8,815            6,012        11,529        26,356          6,018           1,531
  Allowance for borrowed funds used
    during construction and
    capitalized interest.............      (8,356)             229            --        (8,127)        (6,080)         (2,579)
                                         --------         --------      --------     ---------       --------        --------
                                           64,913           23,219        11,828        99,960         56,933          49,743
                                         --------         --------      --------     ---------       --------        --------
INCOME BEFORE OBLIGATED MANDATORILY
  REDEEMABLE PREFERRED SECURITIES....      53,959           25,916        (8,819)       71,056         94,686          90,472
    Preferred dividend requirements
      of mandatorily redeemable
      preferred securities...........     (15,172)          (1,738)           --       (16,910)       (11,013)         (7,256)
INCOME BEFORE PREFERRED DIVIDENDS....      38,787           24,178        (8,819)       54,146         83,673          83,216
    Preferred dividend
      requirements...................         (95)          (2,301)           --        (2,396)          (174)         (1,125)
                                         --------         --------      --------     ---------       --------        --------
INCOME APPLICABLE TO COMMON STOCK....    $ 38,692         $ 21,877      $ (8,819)    $  51,750       $ 83,499        $ 82,091
                                         ========         ========      ========     =========       ========        ========
</TABLE>

                                      S-19
<PAGE>
NEVADA POWER COMPANY OPERATING RESULTS

    On February 4, 2000, the PUCN issued an order that rejected NVP's updated
September 30, 1999 deferred energy filing. In addition, on March 28, 2000 the
PUCN issued a decision that ordered a substantial reduction in NVP's requested
rate relief on the remaining $44 million included in the case. As a result of
these decisions, NVP operating results for 1999 include a pre-tax charge of
$80.0 million. NVP is appealing the PUCN decisions. If not for this charge,
NVP's net income would have been approximately $7 million higher than it was in
1998.

    The causes for significant changes in specific lines comprising the results
of operations for NVP for the years ended are as provided (dollars in thousands
except MWh statistics):

<TABLE>
<CAPTION>
                                        1999                          1998                   1997
                              -------------------------     -------------------------     -----------
                                            CHANGE FROM                   CHANGE FROM
                                AMOUNT      PRIOR YEAR        AMOUNT      PRIOR YEAR        AMOUNT
                              -----------   -----------     -----------   -----------     -----------
<S>                           <C>           <C>             <C>           <C>             <C>
ELECTRIC OPERATING REVENUES:
  Residential...............  $   416,345       9.5%        $   380,299       6.0%        $   358,921
  Commercial................      200,186      13.9%            175,760      11.5%            157,694
  Industrial................      290,409      16.4%            249,390      11.9%            222,837
                              -----------      ----         -----------      ----         -----------
  Retail revenues...........      906,940      12.6%            805,449       8.9%            739,452
  Other.....................       70,322       3.1%             68,233      14.3%             59,696
                              -----------      ----         -----------      ----         -----------
    TOTAL REVENUES..........  $   977,262      11.9%        $   873,682       9.3%        $   799,148
                              ===========      ====         ===========      ====         ===========

  Total retail sales
    megawatt-hours (MWh)....   14,715,000       9.1%         13,491,000       3.7%         13,012,000
                              -----------      ----         -----------      ----         -----------

  Average retail revenue per
    MWh.....................  $     61.63       3.2%        $     59.70       5.1%        $     56.83
</TABLE>

    NVP's residential and commercial electric revenue increased in 1999
primarily due to 6% customer growth for both categories and an energy price
increase of 4% effective March 1999. Industrial electric revenues increased in
1999 primarily due to 7% customer growth and an energy price increase of 4%
effective March 1999. Other electric revenues increased in 1999 due to greater
wholesale electric revenue that was partially offset by lower emission credits
and water rights revenue in 1999.

    Residential, commercial and industrial electric revenues increased in 1998
due to an approximate 6% growth in all customer categories and an energy price
increase of 6% during February 1998. The increase in 1998 revenues was partially
offset by milder weather during the summer of 1998. Other electric revenues
increased as a result of the sale of emission credits and water rights in 1998.

<TABLE>
<CAPTION>
                                          1999                         1998                   1997
                                ------------------------     ------------------------      ----------
                                             CHANGE FROM                  CHANGE FROM
                                  AMOUNT     PRIOR YEAR        AMOUNT     PRIOR YEAR         AMOUNT
                                ----------   -----------     ----------   -----------      ----------
<S>                             <C>          <C>             <C>          <C>              <C>
Total Purchased Power.........  $  338,972      19.4%        $  283,838       2.2 %        $  277,644
Less Imputed Capacity
  Deferral....................  $  (45,372)       --         $       --        --          $       --
                                ----------      ----         ----------      ----          ----------
Purchased Power...............  $  293,600       3.4%        $  283,838       2.2 %        $  277,644

Purchased Power MWh...........   7,861,985      14.2%         6,886,920      (2.7)%         7,078,669
Average cost per MWh of
  Purchased Power.............  $    43.12       4.6%        $    41.21       5.1 %        $    39.22
</TABLE>

    NVP has historically used deferred accounting for energy costs.

                                      S-20
<PAGE>
    NVP's purchased power costs were higher in 1999 resulting from a 14%
increase in the volume purchased related to customer growth and an increase in
the per unit cost of power. This increase in cost was partially offset by a
$45 million adjustment (shown separately above) in 1999 related to the deferral
of the portion of one-part firm power contracts deemed by regulators to be
related to capacity costs rather than energy costs. NVP began deferring these
costs in 1999 to comply with an order from the PUCN. For subsequent developments
regarding these deferred costs, see "Recent Developments--Recent Decisions in
Nevada Power Company Deferred Energy Case" in this prospectus supplement.

    During 1999 the cost of energy continued to exceed the corresponding allowed
revenue component that resulted in a deferral of expense of $9.8 million. This
amount was offset by the recovery of energy costs related to prior years of
$27.3 million.

    In 1998 purchased power costs increased 2.2% primarily due to higher average
unit prices paid for purchased power.

<TABLE>
<CAPTION>
                                          1999                         1998                   1997
                               ---------------------------   ------------------------      ----------
                                               CHANGE FROM                CHANGE FROM
                                 AMOUNT        PRIOR YEAR      AMOUNT     PRIOR YEAR         AMOUNT
                               ----------      -----------   ----------   -----------      ----------
<S>                            <C>             <C>           <C>          <C>              <C>
FUEL FOR POWER GENERATION....  $  154,546          3.2 %     $  149,804       7.8%         $  138,956
MWhs generated...............   9,167,963          3.7 %      8,843,057       7.5%          8,228,100
Average fuel cost per MWH of
  Generated Power............  $    16.86         (0.5)%     $    16.94       0.3%         $    16.89
</TABLE>

    In 1999, NVP's fuel expense increased 3.2%, primarily due to an increase in
volumes generated to accommodate customer growth described previously. In 1998,
fuel expense increased 7.8%, primarily due to increased generation to
accommodate customer growth.

<TABLE>
<CAPTION>
                                                1999                       1998                 1997
                                       ----------------------     ----------------------      --------
                                                  CHANGE FROM                CHANGE FROM
                                        AMOUNT    PRIOR YEAR       AMOUNT    PRIOR YEAR        AMOUNT
                                       --------   -----------     --------   -----------      --------
<S>                                    <C>        <C>             <C>        <C>              <C>
Deferral of energy costs--net.......   $97,238       427.6%       $(29,680)     (50.9)%       $(60,400)
</TABLE>

    As a result of the PUCN decisions described in "Recent Developments--Recent
Decisions in Nevada Power Company Deferred Energy Case", a reserve was
recognized for previously deferred energy and imputed capacity costs with a
charge of $80 million to Deferral of energy costs--net. Also, Deferral of energy
costs--net were higher in 1999 because NVP was granted a price increase to cover
current fuel expense, which allowed NVP to recognize previously deferred costs
currently.

    In 1998, NVP deferred $27.0 million of increased energy costs for collection
in a later period and recognized $2.7 million of energy cost deferrals that had
been deferred prior to 1998. In 1997, NVP deferred $27.8 million of increased
energy costs for collection in a later period and recognized $32.6 million of
energy cost decreases that had been previously deferred.

                                      S-21
<PAGE>
    Recovery of fuel expenses is administered under the state's deferred energy
cost accounting procedures. Under the deferred energy procedure, changes in the
costs of fuel and purchased power are reflected in customer rates through annual
rate adjustments and do not affect income.

<TABLE>
<CAPTION>
                                                1999                        1998                 1997
                                       ----------------------      ----------------------      --------
                                                  CHANGE FROM                 CHANGE FROM
                                        AMOUNT    PRIOR YEAR        AMOUNT    PRIOR YEAR        AMOUNT
                                       --------   -----------      --------   -----------      --------
<S>                                    <C>        <C>              <C>        <C>              <C>
Allowance for other funds used during
  construction.......................  $ 3,713       (58.5)%       $ 8,944         2.1%        $ 8,760
Allowance for borrowed funds used
  during construction................    8,356        37.4 %         6,080       135.8%          2,579
                                       -------       -----         -------       -----         -------
                                       $12,069       (19.7)%       $15,024        32.5%        $11,339
                                       -------       -----         -------       -----         -------
</TABLE>

    NVP's AFUDC was lower in 1999 because of construction completed in May 1999
for the Crystal Transmission Project. In 1998, NVP expended approximately
$100 million more on construction activity than in 1997. The additional costs in
1998 resulted in higher AFUDC.

<TABLE>
<CAPTION>
                                             1999                        1998                 1997
                                    ----------------------      ----------------------      --------
                                               CHANGE FROM                 CHANGE FROM
                                     AMOUNT    PRIOR YEAR        AMOUNT    PRIOR YEAR        AMOUNT
                                    --------   -----------      --------   -----------      --------
<S>                                 <C>        <C>              <C>        <C>              <C>
Other operating expense...........  $141,041        4.7 %       $134,652        9.6 %       $122,811
Maintenance expense...............    50,805        3.5 %         49,082       (5.8)%         52,126
Depreciation and amortization.....    80,644        9.6 %         73,562       11.0 %         66,273
Income taxes......................    19,943      (53.6)%         42,949       (1.2)%         43,478
Interest charges on long-term
  debt............................    64,454       13.1 %         56,995       12.2 %         50,791
Interest charges--other...........     8,815       46.5 %          6,018      293.1 %          1,531
Other Income (expense)--net.......    (1,824)     (60.4)%         (4,602)     (19.8)%         (5,741)
</TABLE>

    NVP's other operating expense increased $6.4 million in 1999 primarily due
to growth related costs for distribution expenses and administrative and general
costs that included group insurance and short-term incentive costs. Other
operating expense increased in 1998 primarily due to increased costs for outside
services, computer software and maintenance, administrative and general salaries
and pension costs.

    The level of NVP maintenance and repair expenses depends primarily upon the
scheduling, magnitude and number of generation unit overhauls at NVP's
generating stations. In 1999 maintenance expense increased by $1.7 million
primarily due to boiler maintenance at the Reid Gardner Generating Station. In
1998, maintenance expense decreased by $3.0 million due primarily to lower
maintenance expense at the Reid Gardner Generating Station.

    NVP Depreciation expense was higher in 1999 because of the addition of
approximately $280 million in depreciable assets during the current year
including the completion of the Crystal Transmission Project in June 1999. Also,
depreciation expense increased $7.3 million in 1998 because of a growing
electric depreciable asset base.

    NVP Income taxes were lower in 1999 due to lower operating income before
taxes. Income taxes for 1998 and 1997 were comparable.

    Interest charges on NVP long-term debt were higher in 1999 due to interest
costs on $130.0 million of unsecured notes issued in March 1999. Interest on
long-term debt increased in 1998 primarily due to the issuance in November 1997
of the new Series 1997A $52.3 million Industrial Development Revenue Bonds
(IDBs) and Series 1997B $20 million Pollution Control Revenue Bonds (PCRBs) and
the remarketing at fixed rates in January 1998 of variable rate revenue bonds,
$76.8 million, Series 1995A, $44, million Series 1995C, $20.3 million,
Series 1995D and $13 million,

                                      S-22
<PAGE>
Series 1995E. See Note 9 of "Notes to Consolidated Financial Statements" for
additional information regarding long-term debt.

    NVP Interest charges--other was higher in 1999 because of interest costs
associated with higher short-term borrowings in 1999. Other interest expense was
also higher in 1998 compared to 1997 due to higher short-term borrowings.

    NVP Other income (expense)--net was lower in 1999 because corporate and
short-term incentive costs were charged to operating expense rather than other
expense during 1999. Other expense was lower in 1998 because of higher costs in
1997 for cancellation fees, adjustments related to the PUCN decision and higher
short-term incentive costs.

SIERRA PACIFIC POWER COMPANY OPERATING RESULTS

    Net income before preferred dividends in 1999 was $71.7 million, a decrease
of $14.3 million compared to 1998. Sierra Pacific Power Company ("SPPC") was
authorized to earn a return on equity of 12% in its Nevada electric operations
and 12% and 11.25%, respectively, in its Nevada gas and water operations. SPPC
earned in excess of its allowed regulated returns for its electric and gas
operations and therefore, under its currently effective rate settlement, SPPC
anticipates it will make refunds to customers reflecting one half of the excess
earnings. Appropriate reserves have been recorded to reflect the anticipated
refunds. California operations were authorized to earn a return on common equity
of 11.6% in 1999.

    Nevada, SPPC's primary jurisdiction, uses a marginal cost method for setting
electric and gas rates by customer class. As a result, changes in sales mix can
result in variations in revenues, regardless of changes in total consumption.

    The components of gross margin are set forth (Dollars in thousands):

<TABLE>
<CAPTION>
                                                  1999       1998       1997
                                                --------   --------   --------
<S>                                             <C>        <C>        <C>
Operating Revenues:
  Electric....................................  $609,197   $585,657   $540,346
  Gas.........................................   100,177     99,532     70,675
  Water.......................................    54,348     49,143     46,519
                                                --------   --------   --------
      Total Revenues..........................  $763,722   $734,332   $657,540
                                                --------   --------   --------

Energy Costs:
  Electric....................................   294,822    271,773    231,473
  Gas.........................................    68,125     65,430     38,135
                                                --------   --------   --------
      Total Energy Costs......................   362,947    337,203    269,608
                                                --------   --------   --------
        Gross Margin..........................  $400,775   $397,129   $387,932
                                                ========   ========   ========

Gross Margin by Segment:
  Electric....................................  $314,375   $313,884   $308,873
  Gas.........................................    32,052     34,102     32,540
  Water.......................................    54,348     49,143     46,519
                                                --------   --------   --------
      Total...................................  $400,775   $397,129   $387,932
                                                ========   ========   ========
</TABLE>

                                      S-23
<PAGE>
    The causes for significant changes in specific lines comprising the results
of operations for the years ended are provided below (Dollars in thousands):

<TABLE>
<CAPTION>
                                         1999                          1998                   1997
                               ------------------------      ------------------------      ----------
                                            CHANGE FROM                   CHANGE FROM
                                 AMOUNT     PRIOR YEAR         AMOUNT     PRIOR YEAR         AMOUNT
                               ----------   -----------      ----------   -----------      ----------
<S>                            <C>          <C>              <C>          <C>              <C>
ELECTRIC OPERATING REVENUES:
  Residential................  $  171,533       1.4 %        $  169,109        3.7 %       $  163,003
  Commercial.................     188,348       5.4 %           178,752        1.9 %          175,386
  Industrial.................     185,771       0.5 %           184,820        4.7 %          176,463
                               ----------      ----          ----------      -----         ----------
  Retail revenues............     545,652       2.4 %           532,681        3.5 %          514,852
  Other......................      63,545      20.0 %            52,976      107.8 %           25,494
                               ----------      ----          ----------      -----         ----------
    TOTAL REVENUES...........  $  609,197       4.0 %        $  585,657        8.4 %       $  540,346
                               ==========      ====          ==========      =====         ==========
  Retail sales in
    megawatt-hours (MWh).....   8,412,853       4.5 %         8,047,650        3.9 %        7,743,799
                               ----------      ----          ----------      -----         ----------
  Average retail revenue per
    MWh......................  $    64.86      (2.0)%        $    66.19       (0.4)%       $    66.49
</TABLE>

    In 1999, residential, commercial and industrial electric revenues increased
due to a 3% increase in both residential and commercial customers and a 7.8%
increase in industrial customers. The increase in residential and industrial
revenues was partially offset by lower use per customer. Residential use per
customer was lower due to milder weather in 1999. Industrial use per customer
was lower primarily because of reduced production by several of SPPC's gold
mining customers as a result of lower gold prices in 1999. The average retail
revenue per MWh was lower for 1999 because of higher revenues from customers
that are charged lower rates per MWh. Other electric revenues were higher due to
a $19.4 million increase in wholesale electric sales. This increase was
partially offset by a $4.3 million reclassification from operating expense to a
contra-revenue in order to reflect a refund resulting from the 1997 earnings
sharing decision by the PUCN. Also, the increase in 1999 revenues was partially
offset by a higher provision for customer refunds and also losses from SPPC's
Pinon Pine subsidiaries.

    In 1998, residential and commercial revenues increased due to 2% and 3%
increases in customers, respectively. Industrial revenues were higher in 1998
because of higher use per customer, primarily in the mining industry where
several of SPPC's customers expanded operations during 1998. The increases in
revenues for residential, commercial and industrial were all partially offset by
a rate reduction that went into effect March 1997. The increase in other
revenues primarily resulted from higher wholesale electric sales and a smaller
charge for customer refunds. Higher wholesale sales in 1998, $33.1 million
compared to $13.3 in 1997, reflect an increased focus on this business
opportunity.

                                      S-24
<PAGE>

<TABLE>
<CAPTION>
                                      1999                           1998                    1997
                            -------------------------      -------------------------      -----------
                                          CHANGE FROM                    CHANGE FROM
                              AMOUNT      PRIOR YEAR         AMOUNT      PRIOR YEAR         AMOUNT
                            -----------   -----------      -----------   -----------      -----------
<S>                         <C>           <C>              <C>           <C>              <C>
GAS OPERATING REVENUES:
  Residential.............  $    42,888       (2.2)%       $    43,833       14.1 %       $    38,410
  Commercial..............       21,259       (3.5)%            22,022       12.3 %            19,606
  Industrial..............       11,252       (9.0)%            12,368        6.8 %            11,580
  Miscellaneous...........        1,305      281.3 %              (720)      (6.2)%              (678)
                            -----------      -----         -----------     ------         -----------
  Total retail revenue....       76,704       (1.0)%            77,503       12.5 %            68,918
  Wholesale revenue.......       23,473        6.6 %            22,029     1153.8 %             1,757
                            -----------      -----         -----------     ------         -----------
  TOTAL REVENUES..........  $   100,177        0.6 %       $    99,532       40.8 %       $    70,675
                            ===========      =====         ===========     ======         ===========
  Sales (Decatherms):
  Retail..................   13,387,819       (5.3)%        14,142,782       13.3 %        12,487,087
  Wholesale...............   10,424,212      (11.2)%        11,738,372     1278.6 %           851,459
                            -----------      -----         -----------     ------         -----------
  Total...................   23,812,031       (8.0)%        25,881,154       94.0 %        13,338,546
                            -----------      -----         -----------     ------         -----------
  Average revenues per
    decatherm
  Retail..................  $      5.73        4.6 %       $      5.48       (0.7)%       $      5.52
  Wholesale...............  $      2.25       19.8 %       $      1.88       (8.7)%       $      2.06
</TABLE>

    Residential, commercial and industrial gas revenues were lower in 1999
because of lower per customer use resulting from milder weather in 1999. Lower
gas revenues in 1999 were partially offset by additional customers in all
categories. Wholesale gas revenues were higher due to several large gas sales
contracts in the first quarter of 1999.

    Residential, commercial and industrial gas revenues increased in 1998
because of a 4% increase in customers and colder than normal weather during the
year. The increase in wholesale revenues reflected the Company's increased focus
on this business opportunity.

<TABLE>
<CAPTION>
                                                 1999                       1998                1997
                                        ----------------------     ----------------------     --------
                                                   CHANGE FROM                CHANGE FROM
                                         AMOUNT    PRIOR YEAR       AMOUNT    PRIOR YEAR       AMOUNT
                                        --------   -----------     --------   -----------     --------
<S>                                     <C>        <C>             <C>        <C>             <C>
WATER OPERATING REVENUES..............  $54,348       10.6%        $49,143        5.6%        $46,519
                                        =======       ====         =======        ===         =======
</TABLE>

    Water revenues increased during 1999 due to a 5% increase in total customers
and higher use per customer as a result of less precipitation in 1999.

    Water revenues were higher in 1998 because of a 3% increase in customers and
an April 1998 price increase.

<TABLE>
<CAPTION>
                                         1999                          1998                   1997
                               ------------------------      ------------------------      ----------
                                            CHANGE FROM                   CHANGE FROM
                                 AMOUNT     PRIOR YEAR         AMOUNT     PRIOR YEAR         AMOUNT
                               ----------   -----------      ----------   -----------      ----------
<S>                            <C>          <C>              <C>          <C>              <C>
PURCHASED POWER..............  $  179,781      14.5 %        $  156,970      20.2 %        $  130,612
Purchased Power MWh..........   5,797,903      25.4 %         4,623,959      20.5 %         3,836,975
Average cost per MWh of
Purchased Power..............  $    31.01      (8.7)%        $    33.95      (0.3)%        $    34.04
</TABLE>

    Purchased power costs were higher in 1999 primarily because SPPC fulfilled
more of its total energy requirements with less expensive purchased power and
reduced its own generation. Purchased power costs were also higher during 1999
due to increased wholesale sales. The higher costs were partially offset by
lower average unit prices for purchased power.

                                      S-25
<PAGE>
    Purchased power costs were significantly higher in 1998 due mostly to the
costs associated with higher wholesale electric sales as discussed previously.
To a lesser extent system load growth also contributed to higher purchased power
costs.

<TABLE>
<CAPTION>
                                         1999                          1998                   1997
                               ------------------------      ------------------------      ----------
                                            CHANGE FROM                   CHANGE FROM
                                 AMOUNT     PRIOR YEAR         AMOUNT     PRIOR YEAR         AMOUNT
                               ----------   -----------      ----------   -----------      ----------
<S>                            <C>          <C>              <C>          <C>              <C>
FUEL FOR POWER GENERATION....  $  115,065       0.2 %        $  114,803      13.8%         $  100,861
MWhs generated...............   4,998,140      (9.5)%         5,524,262      13.7%          4,859,203
Average fuel cost per MWh
of Generated Power...........  $    23.02      10.8 %        $    20.78       0.1%         $    20.76
</TABLE>

    Fuel for generation costs were comparable with the prior year despite a 9.5%
reduction in the volume of electric generation. Higher gas prices and the
absence of Department of Energy co-funding of fuel costs at the Pinon Pine
project contributed to the higher average cost per MWh of generated power.

    The costs of fuel for generation increased in 1998 because of higher
generation requirements needed to meet continued customer growth and greater use
per customer.

<TABLE>
<CAPTION>
                                      1999                           1998                    1997
                            -------------------------      -------------------------      -----------
                                          CHANGE FROM                    CHANGE FROM
                              AMOUNT      PRIOR YEAR         AMOUNT      PRIOR YEAR         AMOUNT
                            -----------   -----------      -----------   -----------      -----------
<S>                         <C>           <C>              <C>           <C>              <C>
GAS PURCHASED FOR RESALE
  Retail..................  $    47,696        7.2 %       $    44,473       21.2%        $    36,703
  Wholesale...............       20,429       (2.5)%            20,957     1371.7%              1,424
                            -----------      -----         -----------     ------         -----------
  Total...................  $    68,125        4.1 %       $    65,430       71.6%        $    38,127
                            ===========      =====         ===========     ======         ===========

GAS PURCHASED FOR RESALE
(DECATHERMS)
  Retail..................   13,501,728       (6.6)%        14,462,505       13.6%         12,727,950
  Wholesale...............   10,424,212      (11.2)%        11,738,372     1278.6%            851,459
                            -----------      -----         -----------     ------         -----------
  Total...................   23,925,940       (8.7)%        26,200,877       92.9%         13,579,409
                            ===========      =====         ===========     ======         ===========

AVERAGE COST PER DECATHERM
  Retail..................  $      3.53       14.6 %       $      3.08        6.9%        $      2.88
  Wholesale...............  $      1.96        9.5 %       $      1.79        7.2%        $      1.67
</TABLE>

    The cost of gas purchased for retail sales increased in 1999 because of
higher unit prices. The increase in gas unit prices is attributable to increased
demand for gas in the Pacific Northwest and additional transportation fees.

                                      S-26
<PAGE>
    Consistent with the increase in retail gas revenues from customer growth and
colder weather in 1998, retail gas purchases (decatherms) were higher in 1998.
The average cost per decatherm for all purchases was also higher because of an
increase in the unit cost of firm and spot purchases.

<TABLE>
<CAPTION>
                                                1999                        1998                 1997
                                       ----------------------      ----------------------      --------
                                                  CHANGE FROM                 CHANGE FROM
                                        AMOUNT    PRIOR YEAR        AMOUNT    PRIOR YEAR        AMOUNT
                                       --------   -----------      --------   -----------      --------
<S>                                    <C>        <C>              <C>        <C>              <C>
Allowance for other funds used during
  construction.......................  $(1,341)     (135.3)%       $ 3,797       (33.7)%       $ 5,723
Allowance for borrowed funds used
during construction..................      308       (95.2)%         6,414        34.0 %         4,785
                                       -------      ------         -------       -----         -------
                                       $(1,033)     (110.1)%       $10,211        (2.8)%       $10,508
                                       -------      ------         -------       -----         -------
</TABLE>

    The total allowance for funds used during construction (AFUDC) was lower in
1999 because of construction completed in June and December 1998 for the Pinon
and Alturas projects, respectively. Also, the 1999 amounts reflect an adjustment
to reverse amounts previously charged to AFUDC of $2.3 million. This adjustment
resulted from a refinement of amounts assigned to specific components of
facilities that were completed at various times and that used differing AFUDC
rates.

    AFUDC was slightly lower in 1998 than 1997. The 1998 amount was lower due to
the completion of the Pinon Pine power project in June 1998.

<TABLE>
<CAPTION>
                                             1999                        1998                 1997
                                    ----------------------      ----------------------      --------
                                               CHANGE FROM                 CHANGE FROM
                                     AMOUNT    PRIOR YEAR        AMOUNT    PRIOR YEAR        AMOUNT
                                    --------   -----------      --------   -----------      --------
<S>                                 <C>        <C>              <C>        <C>              <C>
Other operating expense...........  $115,453       (0.5)%       $116,076      (3.8)%        $120,600
Maintenance expense...............    22,520        1.1 %         22,266      (4.8)%          23,387
Depreciation and amortization.....    77,373       11.4 %         69,435       8.3 %          64,117
Income taxes......................    36,042      (17.2)%         43,550       7.8 %          40,387
Interest charges on long-term
  debt............................    40,263        3.5 %         38,890      (1.8)%          39,609
Interest charges--other...........    11,615       51.7 %          7,659      67.1 %           4,583
</TABLE>

    Other operating expense for 1999 include a $4.5 million adjustment, which
increased expense and reduced revenue related to a rate reserve established in
1998. This was offset by other reductions. Other operating expense was lower in
1998 due to lower costs for stock compensation, post-retirement benefits, fuel
buyouts, lower accruals for delays in the construction of Pinon, and no flood
damage costs.

    Maintenance expense for 1999 was comparable to the prior year. Maintenance
expense was lower in 1998 because of additional electric plant maintenance
performed during the previous year.

    Depreciation and amortization expense increased for 1999 due to the
completion of the Alturas intertie in December 1998 and the Pinon
post-gasification facilities in June 1998. Depreciation expense increased in
1998 because of the Pinon Pine facilities completed in 1998. Also, 1998
depreciation was higher due to water division additions and other customer
improvements added to plant in service late in 1997.

    Operating income taxes were less in 1999 due to lower operating income
before income taxes and a lower effective tax rate for the year. Operating
income taxes increased in 1998 due to increases in pre-tax income and the
effective tax rate.

    Interest on long term debt was slightly higher in 1999 due to higher average
long-term debt balances over the prior year. Interest on long-term debt was
lower in 1998 because of the redemption of $5 million of 8.65% medium-term notes
on June 18, 1998.

                                      S-27
<PAGE>
    Interest charges--other were higher for 1999 because of a Public Utilities
Commission of Nevada's decision to assess partial interest on amounts payable in
the 1997 earnings sharing case and higher average short-term borrowing in 1999.
Interest charges--other increased in 1998 because of higher short-term debt
balances utilized to partially finance the Alturas transmission project.

LIQUIDITY AND CAPITAL RESOURCES

    Overall net cash flows increased slightly during1999, as compared to 1998.
Net cash flows were greater in 1999 due to more cash provided from operating and
financing activities. The increase in cash provided from operating and financing
activities was partially offset by more cash used in investing activities. The
increase in cash flows from operating activities was primarily due to the
collection of revenues related to previously deferred energy costs. Increased
cash from financing activities resulted from the issuance of $456.2 million of
commercial paper by SPR to provide funding of the cash portion of the merger
consideration. Also, NVP issued long-term debt of $130 million senior unsecured
notes, due 2004 and both SPPC and NVP each issued $100 million floating rate
notes in September and October 1999, respectively. Cash utilized for Investing
activities increased primarily as a result of the merger cash requirements. See
Note 2 to the consolidated financial statements included in this report for more
information about the merger cash requirements.

    Overall net cash flows increased during 1998, as compared to 1997, due to
higher net cash from operating and financing activities which were partially
offset by more cash used in investing activities. The increase in cash from
operating activities was mainly due to an energy rate increase effective
February 1, 1998, offset by the deferral of energy cost recovery. The increase
in cash used in investing activities was primarily due to increased construction
expenditures. The increase in net cash used in financing activities was mainly
due to increased short-term borrowing.

CONSTRUCTION EXPENDITURES AND FINANCING

    NEVADA POWER COMPANY

    The table below provides SPR's consolidated cash construction expenditures
and internally generated cash net 1999. The historical information for 1998 and
1997 is NVP information. (Dollars in thousands):

<TABLE>
<CAPTION>
                                                        1999       1998       1997       TOTAL
                                                      --------   --------   --------   ----------
<S>                                                   <C>        <C>        <C>        <C>
Cash construction expenditures*.....................  $729,794   $302,041   204,795    $1,236,630
                                                      ========   ========   =======    ==========
Net cash flow from operating activities.............   211,089    148,281   107,792       467,162
Less common & preferred cash dividends..............   115,833     73,962    81,216       271,011
                                                      --------   --------   -------    ----------
Internally generated cash...........................    95,256     74,319    26,576       196,151
                                                      ========   ========   =======    ==========
Internally generated cash as a percentage of cash
  construction expenditures.........................    13%        25%        13%         16%
</TABLE>

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

*   1999 cash construction expenditures include $448.3 million of merger related
    costs.

                                      S-28
<PAGE>
    SIERRA PACIFIC POWER COMPANY

    The table below provides cash construction expenditures and net internally
generated cash for 1997 through 1999 (dollars in thousands):

<TABLE>
<CAPTION>
                                                        1999       1998       1997      TOTAL
                                                      --------   --------   --------   --------
<S>                                                   <C>        <C>        <C>        <C>
Cash Construction Expenditures......................  $116,131   $139,098   $110,878   $366,107
                                                      ========   ========   ========   ========
Net cash flow from operating activities.............   122,329    153,191    145,455    420,975
Less common & preferred cash dividends..............    81,746     80,459     75,459    237,664
                                                      --------   --------   --------   --------
Internally generated cash...........................    40,583     72,732     69,996    183,311
Add equity contribution from parent.................    22,000     17,250     27,000     66,250
                                                      --------   --------   --------   --------
    Total cash available............................  $ 62,583   $ 89,982   $ 96,996   $249,561
                                                      ========   ========   ========   ========
Internally generated cash as a percentage of cash
  construction expenditures.........................    35%        52%        63%        50%
Total cash available as a percentage of cash
  construction expenditures.........................    54%        64%        87%        68%
</TABLE>

    ESTIMATED COMBINED CONSTRUCTION EXPENDITURES

    SPR's estimated cash construction expenditures for 2000 through 2004 are
$1.6 billion. SPR estimates that 90% of its 2000 cash expenditures of
approximately $308 million will be provided by internally generated funds, with
the remainder being provided by the issuance of long-term debt and short-term
debt.

    The estimated level of internally generated cash utilized for construction
of 90% anticipates that NVP and SPPC will pay all of their net income in
dividends to Sierra Pacific Resources. SPR anticipates subsequently reinvesting
a portion of those dividends in the form of capital contributions of
$44 million of common equity to NVP and $28 million to SPPC in 2000.

CAPITAL STRUCTURE

    On July 28, 1999, immediately following the consummation of the merger with
NVP, SPR put into place a $500 million unsecured revolving credit facility. This
facility may be used for working capital and general corporate purposes,
including for commercial paper backup, and replaced SPR's existing credit
facility. At the same time, SPPC and NVP each put into place a $150 million
unsecured revolving credit facility, which replaced all existing credit
facilities. These two facilities may also be used for working capital and
general corporate purposes, including for commercial paper backup. In addition,
immediately following the merger, SPR and NVP established new commercial paper
programs, SPPC revised its existing commercial paper program, and SPR issued
$456.2 million of commercial paper to provide temporary funding of the cash
portion of the merger consideration.

    As of December 31, 1999, SPR had $463 million of commercial paper issued and
outstanding, NVP had $82 million of commercial paper issued and outstanding and
SPPC had $110 million of commercial paper issued and outstanding. SPR's, NVP's
and SPPC's commercial paper programs are rated A2 and P2 by Standard and Poor's
and Moody's, respectively.

                                      S-29
<PAGE>
    SPR's actual consolidated capital structure at December 31, 1999 and 1998
was as follows. The 1998 capital structure presented is NVP information.
(Dollars in thousands):

<TABLE>
<CAPTION>
                                                              1999                1998
                                                        -----------------   -----------------
<S>                                                     <C>          <C>    <C>          <C>
Short-Term Debt (1)...................................  $  957,688    22%   $  155,380     7%
Long-Term Debt........................................   1,556,627    36%      900,227    43%
Preferred Stock.......................................      50,000     1%        3,265     --
Preferred Securities..................................     237,372     6%      188,872     9%
Common Equity.........................................   1,477,129    35%      864,036    41%
                                                        ----------   ----   ----------   ----
  TOTAL...............................................  $4,278,816   100%   $2,111,780   100%
                                                        ==========   ====   ==========   ====
</TABLE>

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

(1) Including current maturities of long-term debt and preferred stock.

    As of December 31, 1999, under tests required by NVP's first mortgage, NVP
could issue up to $785 million of additional first mortgage bonds at an assumed
interest rate of 8.0%.

    The indenture under which SPPC's first mortgage bonds are issued, prescribes
certain coverage ratios that must be met before additional bonds may be issued.
At December 31, 1999, these coverage provisions would allow for the issuance of
approximately $511 million in additional first mortgage bonds at an assumed
interest rate of 8.0%. The indenture also limits the amount of first mortgage
bonds that SPPC may issue to 60 percent of unfunded property plus the amount of
any previously issued bonds that have since been retired. Based on
certifications to the trustee as of December 31, 1999, these indenture
provisions would have allowed for the issuance of approximately $845 million in
additional first mortgage bonds.

    NVP's secured long-term debt is rated A and Baa1 by Standard & Poor's and
Moody's, respectively. NVP's pre-tax interest coverages for 1999, 1998 and 1997
were 2.35%, 3.22% and 3.59%, respectively.

    SPPC's secured long-term debt is rated A- and A3 by Standard & Poor's and
Moody's, respectively. SPPC's pre-tax interest coverages for 1999, 1998 and 1997
were 3.15%, 3.87% and 3.86%, respectively.

    SPR currently does not have a secured long-term debt rating by Standard &
Poor's or Moody's.

REGULATORY EVENTS

INDUSTRY RESTRUCTURING

    ELECTRIC RESTRUCTURING ACTIVITIES

    In 1997, the Governor of Nevada signed into law Assembly Bill 366 (AB366)
that provided for competition to be implemented in the electric utility
industry.

    In 1999, the Governor signed into law Senate Bill 438 (SB438) that amended
AB366. SB438 contains the following major provisions:

    - In addition to generation, metering and billing are declared to be
      potentially competitive services.

    - The start date for competition is March 1, 2000, or such other start date
      determined to be in the public interest by the Governor.

    - The electric distribution utility is the provider of last resort (PLR)
      until alternate methods go into effect, no sooner than July 1, 2001. PLR
      rates are capped until March 1, 2003 at the rates

                                      S-30
<PAGE>
      in effect as of July 1, 1999, as adjusted for any deferred energy cases
      filed with the PUCN prior to October 1, 1999.

    - Allows the use of the net proceeds of generation divestiture to pay for
      certain reductions in PLR revenues until March 1, 2003 arising from the
      departure of customers who select new energy.

    - Repeals deferred energy charges for electric utilities on October 1, 1999.

    - Permits alternative sellers to submit bids to provide PLR service after
      July 1, 2001, subject to a PUCN public interest finding and a PUCN-held
      auction.

    - Provides for the recovery of Past Costs, often referred to as stranded
      costs, including specific criteria for recovery of purchase power costs.

    The PUCN has conducted a number of hearings associated with AB366 and SB438.
In February 2000 the Governor of Nevada delayed the start date of competition
indefinitely. Electric competition may begin later in 2000 or 2001. Generally,
restructuring regulations have proceeded slowly. Currently, many important
regulations, including the affiliate regulations and the PLR, are not complete.
In their present form several of the proposed regulations could have potentially
significant negative financial ramifications. These regulations and the
potential risks are described below.

    AFFILIATE TRANSACTION RULES AND AFFILIATE APPLICATIONS TO PROVIDE
     POTENTIALLY COMPETITIVE SERVICES

    While SB438 allows the use of name and logo by affiliates, the affiliate
regulation has not yet been modified to reflect this change. The companies have
requested that the PUCN modify the rule related to sharing services, sharing
officers and directors, and transfer pricing. To date the PUCN has not acted on
this request. On March 30, 1999, NVP and SPPC filed with the District Court a
"Complaint and Petition for Declaratory and Injunctive Relief and for Judicial
Review" relating, among other things, to the Affiliate Transaction Rules. SPPC
and NVP asked that the court find that the rules "violate plaintiff's federal
and state constitutional guarantees, are unlawful and invalid because they were
enacted in violation of the procedural and substantive provisions of the
Administrative Procedures Act, and are unlawful and invalid because they exceed
the authority of the PUCN and are unsupported by the evidence." SPC and NVP
asked that the court order the PUCN not to enforce the regulations.

    PAST COSTS

    Past costs, commonly referred to as stranded costs in other jurisdictions,
were the subject of several hearings in 1999. AB366/SB438 permit the recovery of
costs associated with potentially competitive services such as generation and
purchased power pursuant to specified legal criteria. In the hearings various
topics were discussed, including the characteristics that define recoverable
past costs, criteria for evaluating the effectiveness of mitigation efforts,
options for cost recovery mechanisms and applicable tax and accounting issues.

    On December 29, 1999 the PUCN adopted the past cost regulation. This
regulation requires the utility to file for past costs 45 days after the
adoption of the regulation or issuance of the final order in the compliance plan
filing. The regulation requires estimates of book values and market values as of
the opening date of competition. In addition, NVP and SPPC must provide
documentation relative to criteria in the law such as mitigation efforts,
conduct relative to other states, and efforts to minimize taxes. The PUCN will
take these criteria into consideration in determining allowable past costs.
During comments related to this rule, NVP and SPPC raised a number of legal
issues including treatment of purchase power agreements, ability to true up
initial estimates of past costs to actual results, and ability to recover costs
to implement restructuring. NVP and SPPC have not completed an estimate of their
past costs, since such a calculation is dependent on a variety of issues related
to restructuring which are

                                      S-31
<PAGE>
not resolved at this time. However based upon the current regulation and the
positions taken by other parties to the rulemaking, several risk areas have been
identified including:

    - SB438 criteria provides latitude for the PUCN to reduce each company's
      stranded cost claim.

    - Purchased power agreements are the largest category of past costs. Federal
      and state laws provide protection to federally mandated power purchase
      contracts. NVP and SPPC believe that the regulation provides less security
      to recover purchased power costs than provided by federal and state law.

    - Because the regulation does not provide a guaranteed true up to actual
      results, it is possible that stranded cost recovery could be set too low
      to recover all stranded costs.

    - The stranded cost proceeding will establish the gain or loss on sale of
      divestiture of generation; the regulation provides that any gain on
      divestiture would be utilized to reduce stranded costs. Some elements of
      the calculation may be controversial. In addition the regulation does not
      address other claims to generation gain, such as recovery of certain
      revenue shortfalls as allowed by SB438 which arise as customers leave the
      PLR.

    As indicated in "Recent Developments", NVP and SPPC have filed a lawsuit in
United States District Court in Nevada challenging the constitutionality of the
Nevada electric restructuring legislation and regulations.

    PROVIDER OF LAST RESORT

    The provider of last resort (PLR) will provide electric service to customers
who do not select an electricity provider and to customers who are not able to
obtain service from an alternative seller after the date competition begins.

    SB438 provides for the electric distribution utility (EDU) to provide PLR
services until July 1, 2001. The PUCN has conducted several workshops and
hearings on the PLR regulations. This rule is not expected to be finalized until
mid-2000. The current draft proposed regulation includes standards of conduct
relative to distribution and provider of last resort functions, which require
segregation of operating functions and constraints on sharing of common
services. As part of their comments during development of the proposed
regulation, NVP raised concerns regarding the financial impacts of the proposed
regulations that place into question the financial viability of the PLR. For
instance the current regulations restrict the PLR from relying on distribution
assets or revenues to obtain credit. Second, the current regulations provide no
financial reward potential for the significant fuel price risks that the PLR may
face during the PLR rate cap period which ends March 1, 2003. Third, the
proposed standards of conduct for the EDU and PLR will increase costs as a
result of the loss of economies of scale and scope.

    In addition to these impacts, the proposed regulation does not address two
important areas associated with the PLR. Regulations have yet to be developed
that fairly compensate the utilities for recovery of revenue shortfalls allowed
under SB438 which arise as customers leave the PLR for new suppliers.
Regulations also do not address how NVP and SPPC will be able to collect the
costs, allowed by SB438, which will be incurred to serve customers who leave the
PLR and later return.

    In the ongoing rulemaking process NVP and SPPC are working to address these
serious concerns and modify the PLR regulation. If the proposed regulations are
adopted in their current form, NVP and SPPC will seek to transition out of the
PLR function. In addition, if necessary, NVP and SPPC are prepared to pursue
legal remedies to mitigate any significant financial exposures associated with
the final PLR regulation.

                                      S-32
<PAGE>
    INDEPENDENT SCHEDULING ADMINISTRATOR

    NVP and SPPC have participated in interim Independent Scheduling
Administrator (iISA) working groups which are developing iISA standards,
protocols and procedures. The PUCN has held hearings regarding entities
interested in performing the iISA function, the timeline, the functions to be
performed, the costs and how these entities will adhere to the PUCN iISA
principles.

    To date, NVP and SPPC have not agreed to provide funding for the iISA
because the PUCN has not provided a mechanism for NVP and SPPC to recover costs
associated with the ISA. However, in February 2000 the PUCN opened an
investigatory docket to consider the funding and other transmission access
issues. See FERC Matters for further discussion.

    GAS RESTRUCTURING

    To comply with Nevada AB366 for natural gas deregulation, the PUCN has
developed some new natural gas rules. In 1999, little gas restructuring activity
occurred. Two new regulations with respect to gas licensing and gas licensing
fees were adopted by the PUCN in 1999.

NEVADA MATTERS

    NON-PRICE TERMS AND CONDITIONS FOR DISTRIBUTION SERVICE

    On February 2, 1999, NVP filed its non-price terms and conditions for
unbundled distribution service. A stipulation resolving most issues and agreeing
to further filings on unresolved issues was filed with the PUCN and subsequently
approved by the PUCN on April 22, 1999. Settlements regarding the unresolved
issues were subsequently filed and approved by the PUCN.

    On February 1, 1999, SPPC filed its non-price terms and conditions for
unbundled distribution service pursuant to the PUCN regulations. A stipulation
resolving most issues and agreeing to further filings on unresolved issues was
filed with the PUCN on April 9, 1999, and subsequently approved by the PUCN on
April 22, 1999. Settlements regarding the unresolved issues were subsequently
filed and approved by the PUCN.

    UNBUNDLING OF UTILITY SERVICES

    On April 1, 1999, NVP filed the revenue requirements and unbundling study
portions of the Compliance Filing with the PUCN. The filing included the
development of an electric revenue requirement for the test period 1998. The
compliance filing rule requires the revenue requirement development to be in the
same form used for rate cases. In the unbundling study, the revenue requirement
was assigned and allocated to a number of service components including
generation, aggregation, transmission, distribution, metering, billing, and
customer services. On September 23, 1999, the PUCN issued an interim order on
NVP's April 1 compliance filing. The order contained the PUCN's decision on
revenue requirements, return on equity, depreciation, and the unbundling study.
NVP did not utilize the orders revenue requirement, return on equity or
depreciation rates from Phase II of the case because SB438 legally mandated that
NVP use its July 1, 1999 revenue requirement.

    On April 1, 1999, SPPC filed the revenue requirements and unbundling study
portions of the Compliance Filing with the PUCN. The filing included the
development of an electric revenue requirement for the test period 1998. The
compliance filing regulation requires the revenue requirement development to be
in the form used for rate cases. In the unbundling study, the revenue
requirement was assigned and allocated to a number of service components
including generation, aggregation, transmission, distribution, metering,
billing, and customer services. On September 23, 1999, the PUCN issued an
interim order on SPPC's April 1 compliance filing. The order contained the
PUCN's decision on revenue requirements, return on equity, depreciation, and the
unbundling study.

                                      S-33
<PAGE>
SPPC did not utilize the order's revenue requirement, return on equity or
depreciation rates from Phase II of the case because SB438 legally mandated that
SPPC use its July 1, 1999 revenue requirement.

    PRICING OF DISTRIBUTION SERVICE

    On October 12, 1999, NVP filed final versions of the approved non-price
terms and conditions and rates reflecting a revenue requirement thought by NVP
to be correct and in accordance with SB 438. Hearings were held in
January 2000.

    On October 8, 1999, SPPC filed final versions of the approved non-price
terms and conditions and rates reflecting a revenue requirement thought by SPPC
to be correct and in accordance with SB 438. Hearings were held in early
November. A decision is expected in 2000.

    MERGER OF SIERRA PACIFIC RESOURCES AND NEVADA POWER

    On April 8, 1998, NVP and SPPC filed a joint application with the PUCN for
approval of their proposed merger. On January 4, 1999, the PUCN issued the final
order in the merger case. On December 31, 1998, the PUCN voted 3-0 to approve
the merger, with conditions. The conditions include, among others, requirements
to divest generation, file the divestiture plan with the Commission for
approval, file an ISA proposal with the FERC, file a generation tariff with the
FERC, file a rate case and unbundle costs in 1999, file a subsequent rate case
three years after retail competition, and submit application to recover stranded
costs.

    DEFERRED ENERGY FILING

    Senate Bill 438 froze the rates for NVP at the level that was in effect on
July 1, 1999, except that the PUCN was authorized to modify those rates in
decisions related to deferred energy cases filed by NVP prior to October 1,
1999. Accordingly, NVP filed a deferred energy case on July 15, 1999, covering
the period from June 1, 1998 through May 31, 1999. On September 30, 1999, NVP
filed an amendment to its deferred energy case, covering the additional period
through August 31, 1999. On February 4, 2000, the PUCN issued an order that
rejected NVP's September 30, 1999 amendment to its deferred energy filing. In
addition, on March 28, 2000, the PUCN issued a decision that ordered a
substantial reduction in NVP's requested rate relief on the remaining
$44 million included in the case. See "Recent Developments--Recent Decisions in
Nevada Power Deferred Energy Cases".

    As a result of these decisions, NVP recognized a reserve for previously
deferred energy and imputed capacity costs of $80 million. $56 million of the
reserve is associated with the February 4 decision and $24 million is associated
with the March 21 decision. NVP has appealed the PUCN decisions.

    EARNINGS SHARING

    On April 30, 1999, SPPC filed its second compliance filings related to the
1997 rate stipulation The filings provide a calculation of SPPC's electric and
gas earnings in excess of a 12% return on equity (ROE). Any earnings in excess
of 12% ROE are shared 50/50 between shareholders and customers. On August 19,
1999, the PUCN approved a stipulation between SPPC, Staff, and the UCA that
rebated $7.37 million and $1.98 million to electric and gas customers,
respectively, in 1999. Based on 1999 operating results, SPPC anticipates it may
make refunds to customers. Appropriate reserves have been recorded to reflect
any anticipated refunds.

                                      S-34
<PAGE>
    GENERATION DIVESTITURE

    SPPC and NVP filed with the PUCN a request for approval to sell their
respective generation plants on October 12, 1999. On February 18, 2000, the PUCN
approved an application to sell the generation plants of both SPPC and NVP. The
revised divestiture plan was approved unanimously by the Commission. Under the
terms of the approved plan, both utilities will sell all of their power plants
through an auction process.

CALIFORNIA MATTERS

    RATE REDUCTION BONDS

    California's electricity restructuring statute (Assembly Bill 1890, Chapter
854, California Statutes of 1996, as amended), permits California investor-owned
utilities, including SPPC, to finance the recovery of a reduction in electricity
rates for residential and small commercial customers through the issuance of
rate reduction certificates. Transition costs consist of the costs of
generation-related assets and obligations that may become uneconomic as a result
of a competitive generation market, together with certain other costs associated
therewith.

    In order for SPPC to recover transition and associated costs, the California
Public Utilities Commission (CPUC) authorized the establishment of
non-bypassable, usage-based, per kilowatt hour charges (FTA Charges), to be
included in the regular utility bills of residential and small commercial
consumers located in the historical service territory of SPPC in California. The
right to receive payments made in respect of the FTA Charges is referred to as
Transition Property.

    On April 9, 1999, SPPC sold the Transition Property to SPPC Funding LLC, a
Delaware special purpose limited liability company whose sole member is the
Company, in exchange for the proceeds of the SPPC Funding LLC Notes,
Series 1999-1 (Underlying Notes). SPPC Funding LLC then issued and sold the
Underlying Notes to the California Infrastructure and Economic Development Bank
Special Purpose Trust SPPC-1 (Trust) in exchange for the proceeds of the sale of
the Trust's $24.0 million 6.4% Rate Reduction Certificates, Series 1999-1
(Certificates). The Trust, which had been established by the California
Infrastructure and Economic Development Bank, issued and sold the Certificates
in a private placement pursuant to Rule 144A under the Securities Act of 1933,
as amended. The Certificates are one of a series of rate reduction certificates
that may be issued from time to time by the Trust and sold to investors upon
terms determined at the time of sale.

    On January 10, 2000, the CPUC approved SPPC's annual true-up of the FTA
charges effective January 1, 2000.

    REVENUE CYCLE UNBUNDLING

    On February 18, 1999, the CPUC approved SPPC's proposed Revenue Cycle
Services Credits (RCSC) application filed February 2, 1998. The RCSC addresses
meter ownership, meter services, meter reading, and billing and applies to
customers who select their own provider of a revenue cycle service. On April 9,
1999, SPPC made a compliance tariff filing which reflects the approved credits.

    DIRECT ACCESS TARIFFS

    On April 5, 1999, the CPUC approved SPPC's compliance filing, effective back
to March 18, 1998, which proposed tariff changes to implement direct access.

    RATE UNBUNDLING

    On April 5, 1999, the CPUC approved SPPC's proposed unbundled rates
effective back to June 1, 1998.

                                      S-35
<PAGE>
    DISTRIBUTION COMPETITION

    The CPUC has opened a docket item to solicit comments and proposals on
distributed generation and competition in electric distribution service. SPPC is
actively participating in the on-going workshops. It is too early to determine
how this proceeding may affect SPPC.

    GENERATION DIVESTITURE

    SPPC has filed with the CPUC its request for approval to sell its generation
plants. SPPC plans to file a revised application during the first half of 2000.

    DISTRIBUTION PERFORMANCE-BASED RATE-MAKING (PBR)

    On January 3, 2000, SPPC filed a distribution PBR proposal to become
effective January 1, 2001 through 2003. The proposal includes rate indexing and
earnings sharing mechanisms as well as performance indicators for employee
safety, customer satisfaction and system reliability. SPPC will submit a 2001
Cost of Capital filing in May 2000 and a Distribution PBR 2001 Cost of Service
filing in June 2000.

FERC MATTERS

    ALTURAS

    On April 15, 1999, the FERC approved the settlement in the Import Limit Case
which had previously been certified by the Administrative Law Judge in
June 1998. The settlement provides that, until February 28, 2001, Truckee Donner
Public Utility District (TDPUD) will receive 30 MW of import capability. After
February 28, 2001, allocation of import capacity will be determined by the FERC
based on the results of SPPC's 1998 Resource Plan and a subsequent filing with
the FERC in 1999.

    REGIONAL TRANSMISSION ORGANIZATIONS

    On May 13, 1999, the FERC issued a Notice of Proposed Rulemaking on Regional
Transmission Organizations (RTOs). The FERC proposed characteristics of an RTO
and also the requirement for utilities to form or join RTOs.

    On August 23, 1999, SPPC filed comments on the proposed rule along with
numerous other parties. On December 15, 1999, the FERC approved the final rule
on RTOs.

    MERGER

    On April 14, 1999, the FERC voted to approve the merger of SPR and NVP, as
proposed. In approving the merger the FERC required the companies to divest
their generation facilities (as proposed by the companies) and required NVP to
file an update of its transmission rates (also proposed by the companies).

    On May 17th, TDPUD filed a Petition for Rehearing of the FERC's order
approving the merger. TDPUD claims the FERC violated its own policy by allowing
the merger to be consummated prior to divestiture of generation assets. NVP and
SPCC filed an answer to TDPUD's Petition for Rehearing in May. On July 14, 1999,
the FERC denied all aspects of TDPUD's petition.

    TRANSMISSION RATE CASES

    On May 29, 1999, NVP filed an application with the FERC to increase its Open
Access Transmission rates. On November 24, 1999, an unopposed motion to suspend
the procedural schedule

                                      S-36
<PAGE>
to allow consummation of a settlement was filed with the FERC. The Settlement
was filed on February 8, 2000 and the rates became effective on March 1, 2000.

    On March 30, 1999, SPPC filed with the FERC to increase its Open Access
Transmission rates. SPPC requested an increase of $16 million in the annual
revenue requirement for network service. The point-to-point rate would increase
from $2.80 /kW-mo. to $3.21 /kW-mo. This filing incorporates the Alturas
intertie, completed in December 1998, and the reclassification of transmission
and distribution facilities approved by the PUCN last summer.

    On May 28, 1999, as expected, the FERC issued an order setting the rate case
for hearing. The proposed rates are accepted subject to refund and suspended
until November 1, 1999. On June 14, 1999, as required by the May 28 order, SPPC
filed additional information on the proposed transmission and distribution (T&D)
reclassification. SPPC also requested that the FERC accept the filing and
approve the T&D split. On July 29, 1999 the FERC accepted the Company's proposed
T&D reclassification.

    On October 12, 1999, SPPC filed an Offer of Partial Settlement which
resolved all issues but pricing to the Mines and to the City of Fallon. On
November 3, the Partial Settlement was certified to the FERC. A status report on
the two remaining issues was filed on January 11, 2000. On January 31, 2000, the
FERC approved the Partial Settlement.

    GENERATION TARIFFS

    On March 31, 1999, NVP filed with the FERC for approval of generation
tariffs which contain the rates, terms and conditions under which the new owners
of NVP's generation would operate after divestiture. The FERC approved the
tariffs on November 1, 1999. In compliance with the FERC's November 1 order, NVP
filed pro forma service agreements for the approved tariffs which were
subsequently approved on December 16, 1999.

    On March 31, 1999, SPPC filed Docket No. ER99-2332 with the FERC for
approval of generation tariffs that contain the rates, terms and conditions
under which the new owners of SPPC's generation would operate after divestiture.
The tariffs permit market-based rates after the offering of capacity under a
cost-based recourse approach.

    Motions to intervene and protest in SPPC's generation tariffs rate case were
due on April 20, 1999. Newmont, City of Fallon, and TDPUD filed motions to
intervene and protest. Barrick (a mining company) filed a motion to intervene
with comments. Several other parties also filed interventions. The PUCN filed
motion to intervene and protest one day after the date established by the FERC.
The PUCN requested the FERC to hold the proceedings in abeyance to allow the
PUCN more time to review Sierra's divestiture plan filing.

    SPPC filed an Answer to the protests filed on the tariff on May 5, 1999. In
response to the PUCN request, SPPC requested that the FERC rule on SPPC's tariff
by November 30, 1999 (rather than September 30, 1999) to allow the PUCN more
time. SPPC also provided clarification in response to other protests.

    On July 20, 1999, SPPC filed a motion to expedite the FERC's consideration
of the tariff. The motion requested that the FERC approve the tariff by
September 30, 1999 since the PUCN issues were resolved.

    On November 1, the FERC dismissed the tariffs, apparently misinterpreting
the agreement reached with the PUCN on the tariffs. On November 22, 1999, SPPC
filed a request for rehearing of the FERC's November 1 order dismissing the
tariffs. The rehearing request explains how the FERC erred in dismissing the
tariff. On December 17, 1999, the Commission issued an Order Granting Rehearing
for Further Consideration. A decision is expected in 2000.

                                      S-37
<PAGE>
    INDEPENDENT SCHEDULING ADMINISTRATOR (ISA)

    On July 23, 1999, SPPC and NVP submitted a filing to establish the Mountain
West ISA (Docket ER97-3719). The proposal centers on the formation of an interim
ISA called Mountain West ISA, which will ensure the non-discriminatory treatment
of transmission customers in two wholesale electricity markets; one in northern
Nevada and one in southern Nevada. The formation of the ISA is viewed as an
interim step in the move to broader regional restructuring of the electric
service industry in the western United States.

    Fifteen parties filed to intervene in the ISA filing. On September 17, 1999,
SPPC, Nevada Power and the Mountain West ISA filed answers to the protests filed
on the ISA filing. The California ISO filed an answer to SPPC's and Nevada
Power's response to their protest on September 28, 1999.

    On January 27, 2000, the FERC issued an order approving with modifications
the Mountain West ISA proposal. The PUCN is continuing to review aspects of the
filing, including funding for the Mountain West ISA.

                                      S-38
<PAGE>
                            DESCRIPTION OF THE NOTES

    The following description of the terms of the notes supplements the
description of the general terms and provisions of Debt Securities contained in
the accompanying prospectus. To the extent the following description is
inconsistent with any part of the description of Debt Securities contained in
the prospectus, then the following description replaces the description in the
prospectus.

    The notes will be issued under an indenture (we refer to the indenture, as
supplemented from time to time, as the "Indenture") between Sierra Pacific
Resources and The Bank of New York as Trustee.

    The following summary of certain provisions of the notes and the Indenture
is not complete and is subject to the detailed provisions of the Indenture. We
have filed a copy of the Indenture as an exhibit to the registration statement
we have filed with the SEC. Whenever particular provisions or defined terms in
the Indenture are referred to in this prospectus supplement, those provisions or
defined terms are incorporated by reference in this prospectus supplement.

TERMS

    The notes issued under the Indenture will mature on May 15, 2005. The notes
will be unsecured obligations of Sierra Pacific Resources and will rank equally
with all of our other unsecured and unsubordinated indebtedness. The notes will
initially be issued in an aggregate principal amount of $300 million, although
we may "reopen" the note series and issue additional notes.

    The notes will bear interest at the rate shown on the front cover of this
prospectus supplement from May 9, 2000, payable semi-annually on each May 15 and
November 15 to the persons in whose name they are registered at the close of
business on May 1 or November 1 preceding the interest payment date. Interest on
the notes will be calculated on the basis of a 360-day year of twelve 30-day
months.

    The first interest payment on the notes will be made on November 15, 2000.

    The notes may be redeemed before their maturity as described below, but are
not entitled to the benefit of any sinking fund. They will be issued in
book-entry form only. See "Book-Entry System."

    If any Interest Payment Date, redemption date or Maturity Date would
otherwise be a day that is not a Business Day, the related payment of principal
and interest will be made on the next succeeding Business Day as if it were made
on the date such payment was due, and no interest will accrue on the amounts so
payable for the period from and after such date to the next succeeding Business
Day.

    The notes will rank equally with all of our unsecured and unsubordinated
debt. As a holding company, our cash flows and our ability to service our debt
are dependent on the cash flows of our subsidiaries. Our subsidiaries are
separate and distinct legal entities and will have no obligation to pay any
amounts due under the debt securities. In addition, our two largest
subsidiaries, Nevada Power Company and Sierra Pacific Power Company, are subject
to regulation by state utility commissions which may impose limitations on the
rate of return on equity or otherwise impact the amount of dividends which may
be paid by those companies. Moreover, the articles of incorporation of Sierra
Pacific Power Company contain restrictions on the payment of dividends on that
subsidiary's common stock if there is currently a default in the payment of
dividends on that company's preferred stock. Similarly, the terms of certain
outstanding series of first mortgage bonds of both Nevada Power Company and
Sierra Pacific Power Company contain quantitative limits on the amount of
dividends that may be paid on that company's common stock. Finally, the bank
credit facilities of Nevada Power Company and Sierra Pacific Power Company
prohibit the payment of dividends on each company's common stock if that company
is in default under its credit facility. As a result of these factors, the notes
will be effectively subordinated to all indebtedness and other liabilities of
our subsidiaries.

                                      S-39
<PAGE>
    If we issue any debt securities within 12 months following the date of this
prospectus supplement and those debt securities have the benefit of any covenant
that is more favorable to the holders than the covenants applicable to the
notes, then the company will amend the Indenture to make a similar covenant for
the holders of the notes.

OPTIONAL REDEMPTION

    The notes will be redeemable, as a whole or in part, at our option, at any
time or from time to time, at a redemption price equal to the greater of:

    (1) 100% of the principal amount of the applicable series of notes to be
       redeemed, and

    (2) the sum of the present values of the remaining scheduled payments of
       principal and interest on the applicable series of notes to be redeemed
       discounted to the date of redemption on a semi-annual basis (assuming a
       360-day year consisting of twelve 30-day months) at the applicable
       Treasury Rate, plus 25 basis points.

In the case of each of clause (1) and (2), accrued interest will be payable to
the redemption date.

    Holders of notes to be redeemed will receive a redemption notice by
first-class mail at least 30 days but not more than 60 days before the date
fixed for redemption. If fewer than all of the notes are to be redeemed, then
not more than 60 days before the redemption date the Trustee will select the
particular notes or portions of notes for redemption from the outstanding notes
not previously called, using a method that the Trustee deems fair and
appropriate.

    On and after the redemption date, interest will no longer accrue on the
notes or any portion of the notes called for redemption unless we default in the
payment of the redemption price and accrued interest. On or before the
redemption date, we will deposit with a paying agent (or the Trustee) money
sufficient to pay the redemption price of and accrued interest on the notes to
be redeemed on that date. If less than all of the notes are to be redeemed, the
notes to be redeemed shall be selected by the Trustee by such method as the
Trustee shall deem fair and appropriate.

    CERTAIN DEFINITIONS

    The following are defined terms relating to the notes.

    "Business Day" means any day that is not a Saturday, a Sunday or a day on
which banking institutions or trust companies in New York City are authorized or
obligated by law to close.

    "Comparable Treasury Issue" means the U.S. Treasury security selected by an
Independent Investment Banker as having a maturity comparable to the remaining
term of the notes to be redeemed that would be utilized, at the time of
selection and in accordance with customary financial practice, in pricing new
issues of corporate debt securities of comparable maturity to the remaining term
of such notes.

    "Comparable Treasury Price" means, with respect to any redemption date,
(1) the average of the Reference Treasury Dealer Quotations for such redemption
date, after excluding the highest and lowest Reference Treasury Dealer
Quotations, or (2) if the Trustee obtains fewer than four such Reference
Treasury Dealer Quotations, the average of all such quotations.

    "Independent Investment Banker" means one of the Reference Treasury Dealers
appointed by the Trustee after consultation with us.

    "Reference Treasury Dealer" means each of Merrill Lynch, Pierce, Fenner &
Smith Incorporated, Credit Suisse First Boston, Salomon Smith Barney and at
least two other entities chosen by Sierra Pacific, or their affiliates which are
primary U.S. government securities dealers, and their respective successors;
provided, however, that if that company ceases to be a primary U.S. Government
securities

                                      S-40
<PAGE>
dealer in New York City (a "Primary Treasury Dealer"), we will substitute
another Primary Treasury Dealer.

    "Reference Treasury Dealer Quotations" means, with respect to each Reference
Treasury Dealer and any redemption date, the average, as determined by the
Trustee, of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) quoted in
writing to the Trustee at 3:30 p.m., New York City time, on the third Business
Day preceding such redemption date.

    "Treasury Rate" means, with respect to any redemption date, the rate per
annum equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
such redemption date.

    BOOK ENTRY SYSTEM

    The notes initially will be represented by one or more global securities
deposited with The Depository Trust Company ("DTC") and registered in the name
of DTC's nominee. DTC will credit on its book-entry registration and transfer
system the accounts of persons designated by the underwriters with the
respective principal amounts of the notes represented by the global security.
Ownership of beneficial interests in a global security is limited to persons
that have accounts with DTC or its nominee ("participants") or persons that may
hold interests through participants. Ownership of beneficial interests in a
global security will be shown on, and the transfer of that ownership may be
effected only through, records maintained by DTC or its nominee (for interests
of persons who are participants) and records maintained by participants (for
interests of persons who are not participants). The laws of some states require
that certain purchasers of securities take physical delivery of the securities
in definitive form. Those limits and laws may impair a purchaser's ability to
transfer beneficial interests in a global security.

    DTC or its nominee will be considered the sole owner or holder of the notes
represented by a global security for all purposes under the Indenture. Except as
provided below, owners of beneficial interests in a global security will not be
entitled to have notes represented by the global security registered in their
names, will not receive or be entitled to receive physical delivery of notes,
and will not be considered the owners of record or holders of notes under the
Indenture.

    We will make principal and interest payments on notes registered in the name
of DTC or its nominee to DTC or its nominee as the registered holder of the
relevant global security. None of us, the Trustee, any paying agent nor the
registrar for the notes will have any responsibility or liability for any aspect
of the records relating to, or payment made on account of, beneficial interests
in a global security or for maintaining, supervising or reviewing any records
relating to such beneficial interests.

    We expect that DTC or its nominee, upon receipt of any payment of principal
or interest, will credit immediately participants' accounts with payments in
amounts proportionate to their respective beneficial interests in the principal
amount of the relevant global security as shown on the records of DTC or its
nominee. We also expect that payments by participants to owners of beneficial
interests in a global security held through such participants will be governed
by standing instructions and customary practices, as is the case with securities
held for the accounts of customers in bearer form or registered in "street
name," and will be the responsibility of such participants.

    If DTC at any time is unwilling or unable to continue as a depository and we
do not appoint a successor depository within 90 days, we will issue notes in
definitive form in exchange for the entire global security. In addition, we may
at any time and in our sole discretion determine not to have notes represented
by a global security and, in such event, we will issue notes in definitive form
in exchange for the entire global security. If any such instance, an owner of a
beneficial interest in a global security

                                      S-41
<PAGE>
will be entitled to physical delivery in definitive form of notes represented by
such global security equal in principal amount to such beneficial interest and
to have such notes registered in the owner's name. Notes so issued in definitive
form will be issued as registered notes in denominations of $1,000 and integral
multiples thereof, unless we specify otherwise.

    The information in this section concerning DTC and its book-entry system has
been obtained from sources that we believe to be reliable, but we do not take
responsibility for its accuracy.

CONCERNING THE TRUSTEE

    The Bank of New York, Trustee under the Indenture, is a member of the
syndicate of lenders for our credit facility.

                    UNITED STATES FEDERAL TAX CONSIDERATIONS

    The following is a summary of material U.S. federal income tax consequences
and material U.S. federal estate tax consequences of the acquisition, ownership
and disposition of the notes by investors. The "issue price" is generally the
first price at which a substantial amount of the notes is sold from their
original issuance other than to bond houses, brokers, or similar persons or
organizations acting in the capacity of underwriters, placement agents or
wholesalers. Because the amount payable at maturity will not exceed the issue
price by more than a DE MINIMIS amount, as those amounts and issue price are
determined under the Internal Revenue Code and Treasury Regulations thereunder,
the following discussion assumes the notes will not be issued with original
issue discount for federal income tax purposes.

    This summary does not discuss all of the aspects of U.S. federal income and
estate taxation that may be relevant to investors in light of their particular
investment or other circumstances. In addition, this summary does not discuss
any U.S. state or local income or foreign income or other tax consequences. This
summary is based upon the provisions of the Internal Revenue Code of 1986, as
amended, the Treasury Regulations and administrative and judicial
interpretations of the Internal Revenue Code, all as in effect as of the date of
this prospectus supplement and all of which are subject to change or differing
interpretation, possibly with retroactive effect. The discussion below deals
only with the notes held as capital assets as defined in Section 1221 of the
Internal Revenue Code, which is generally property held for investment, and does
not address purchasers of the notes that may be subject to special rules,
including, without limitation, certain U.S. expatriates, financial institutions,
insurance companies, tax-exempt entities, dealers in securities or currencies,
traders in securities, persons who have a functional currency other than the
U.S. dollar, and persons that hold the notes as part of a straddle, hedge,
conversion or other integrated transaction. Prospective investors should consult
their own tax advisors regarding the particular U.S. federal, state and local
and foreign income and other tax consequences of acquiring, owning and disposing
of the notes that may be applicable to them.

    For purposes of the following discussion, a U.S. holder is a beneficial
owner of a note that is, for U.S. federal income tax purposes:

    - an individual citizen or resident of the United States;

    - a corporation or partnership, unless the Internal Revenue Service provides
      otherwise by Treasury Regulation, created or organized in or under the
      laws of the United States or any of its political subdivisions;

    - an estate the income of which is subject to U.S. federal income taxation
      regardless of its source; or

                                      S-42
<PAGE>
    - a trust if, in general, the trust is subject to the supervision of a court
      within the United States and the control of one or more United States
      persons as described in section 7701(a)(30) of the Internal Revenue Code.

    THE FOLLOWING DISCUSSION OF CERTAIN FEDERAL TAX CONSEQUENCES IS FOR GENERAL
INFORMATION ONLY AND IS NOT TAX ADVICE. ACCORDINGLY, INVESTORS CONSIDERING THE
PURCHASE OF NOTES SHOULD CONSULT THEIR OWN TAX ADVISORS WITH RESPECT TO THE
APPLICATION OF THE UNITED STATES FEDERAL INCOME AND ESTATE TAX LAWS TO THEIR
PARTICULAR SITUATION AS WELL AS ANY TAX CONSEQUENCES ARISING UNDER THE LAWS OF
ANY STATE, LOCAL OR FOREIGN TAXING JURISDICTION OR UNDER ANY APPLICABLE TAX
TREATY.

UNITED STATES FEDERAL INCOME TAXATION OF U.S. HOLDERS

    PAYMENT OF INTEREST

    Stated interest on a note generally will be includable in the income of the
U.S. holder of such note as ordinary income at the time such interest is
received or accrued, in accordance with such holder's method of accounting for
United States federal income tax purposes.

    AMORTIZABLE BOND PREMIUM

    If a U.S. holder purchases a note for an amount in excess of the principal
amount, the holder will be considered to have purchased the note at a "premium."
A U.S. holder generally may elect to amortize the premium over the remaining
term of the note on a constant yield method. However, if the note is purchased
at a time when the note may be optionally redeemed for an amount that is in
excess of its principal amount, special rules would apply that could result in a
smaller premium eligible for amortization during the call period and a deferral
of the amortization of bond premium until later in the term of the note. The
amount amortized in any year will be treated as a reduction of the U.S. holder's
interest income from the note. Bond premium on a note held by a U.S. holder that
does not make such an election will decrease the gain or increase the loss
otherwise recognized on disposition of the note. The election to amortize
premium on a constant yield method, once made, applies to all debt obligations
held or subsequently acquired by an electing U.S. holder on or after the first
day of the first taxable year to which the election applies and may not be
revoked without the consent of the Internal Revenue Service.

    SALE, EXCHANGE OR RETIREMENT OF THE NOTES

    Upon the sale, exchange or redemption of a note, a U.S. holder generally
will recognize capital gain or loss equal to the difference between:

    (1) the amount of cash proceeds and the fair market value of any property
       received on the sale, exchange or redemption (except to the extent such
       amount is attributable to accrued interest income not previously included
       in income, which is taxable as ordinary income); and

    (2) such holder's adjusted tax basis in the note. A holder's adjusted tax
       basis in a note generally will equal the cost of the note to the U.S.
       holder, increased by any market discount previously included in the
       income of the U.S. holder with respect to the note, and decreased by any
       bond premium therefor amortized by the U.S. holder with respect to the
       note. Such capital gain or loss will be long-term capital gain or loss if
       the note was held by the U.S. holder for more than 12 months. The net
       capital gain of an individual derived in respect of the notes generally
       will be taxed at a maximum rate of 20% if it is long-term capital gain.

    MARKET DISCOUNT

    If a U.S. holder, other than a holder who purchases the notes from the
initial purchasers, purchases a note for an amount that is less than its
principal amount, the amount of the difference will

                                      S-43
<PAGE>
be treated as "market discount" for United States federal income tax purposes,
unless such difference is less than a specified DE MINIMIS amount. Under the
market discount rules, a U.S. holder will be required to treat any partial
principal payment on, or any gain on the sale, exchange, retirement or other
disposition of, a note as ordinary income to the extent of the market discount
which has not previously been included in income and is treated as having
accrued on such note at the time of such payment or disposition. In addition,
the U.S. holder may be required to defer, until the maturity of the note or its
earlier disposition in a taxable transaction, the deduction of all or a portion
of the interest expense on any indebtedness incurred or continued to purchase or
carry such note.

    Any market discount will be considered to accrue ratably during the period
from the date of acquisition to the maturity date of the note, unless the U.S.
holder elects to accrue on a constant interest method. A U.S. holder may elect
to include market discount in income currently as it accrues (on either a
ratable or constant interest method), in which case the rule described above
regarding deferral of interest deductions will not apply. This election to
include market discount in income currently, once made, applies to all market
discount obligations acquired on or after the first taxable year to which the
election applies and may not be revoked without the consent of the Internal
Revenue Service (IRS).

    INFORMATION REPORTING AND BACKUP WITHHOLDING

    In general, information reporting requirements will apply to payments of
principal, premium, if any, and interest of a note and payments of the proceeds
of the sale of a note to certain noncorporate holders, and a 31% backup
withholding tax may apply to such payments if the U.S. holder:

    (1) fails to furnish or certify his correct taxpayer identification number
       to the payer in the manner required;

    (2) is notified by the IRS that he has failed to report payments of interest
       and dividends properly;

    (3) under certain circumstances, fails to certify that he has not been
       notified by the IRS that he is subject to backup withholding for failure
       to report interest and dividend payments; or

    (4) the IRS notifies us or our paying agent that the taxpayer identification
       number furnished by the U.S. holder is incorrect.

    Any amounts withheld under the backup withholding rules from a payment to a
U.S. holder will be allowed as a credit against such holder's U.S. federal
income tax and may entitle the holder to a refund, provided that the required
information is furnished to the IRS.

MATERIAL U.S. FEDERAL INCOME AND ESTATE TAX CONSEQUENCES TO NON-U.S. HOLDERS

    For purposes of the following discussion, a non-U.S. holder is a beneficial
owner of a note that is not, for U.S. federal income tax purposes, a U.S.
holder. An individual may, subject to exceptions, be deemed to be a resident
alien, as opposed to a non-resident alien, by virtue of being present in the
United States on at least 31 days in the calendar year and for an aggregate of
at least 183 days during a three year period ending in the current calendar
year. For this purpose the number of days an individual is present in the U.S.
includes all of the days present in the current year, one-third of the days
present in the immediately preceding year, and one-sixth of the days present in
the second preceding year. A holder of a note who is treated as a resident alien
under this rule is a U.S. holder for purposes of this summary.

                                      S-44
<PAGE>
    Under present U.S. federal income and estate tax law and subject to the
discussion of backup withholding below:

    (1) payments of principal, premium, if any, and interest on a note by us or
       any of our agents to any non-U.S. holder will not be subject to
       withholding of U.S. federal income tax, provided that in the case of
       interest:

       - the non-U.S. holder does not directly or indirectly, actually or
         constructively, own 10% or more of the total combined voting power of
         all classes of our stock entitled to vote;

       - the non-U.S. holder is not a controlled foreign corporation that is
         related to us through sufficient stock ownership, or a bank receiving
         interest described in Section 881(c)(3)(A) of the Internal Revenue
         Code; and

       - either the beneficial owner of the note certifies to us or our agent,
         under penalties of perjury, that it is not a "United States person"
         under the meaning of the Internal Revenue Code and provides its name
         and address, or a securities clearing organization, bank or other
         financial institution that holds customers' securities in the ordinary
         course of its trade or business that holds the note on behalf of the
         beneficial owner certifies to us or our agent under penalties of
         perjury that it, or the financial institution between it and the
         beneficial owner, has received from the beneficial owner a statement,
         under penalties of perjury, that it is not a "United States person" and
         provides the payor with a copy of this statement;

    (2) a non-U.S. holder will not be subject to U.S. federal income tax on any
       gain or income realized on the sale, exchange, redemption, retirement at
       maturity or other disposition of a note, (except in the case of proceeds
       representing accrued interest, for which the conditions described in
       paragraph (1) above must be met), unless:

       - the non-U.S. holder is an individual who is present in the United
         States for 183 days or more during the taxable year and some other
         conditions are met; or

       - the gain is effectively connected with the conduct of a U.S. trade or
         business by the non-U.S. holder, or if an income tax treaty applies, is
         generally attributable to a U.S. "permanent establishment" maintained
         by the non-U.S. holder; and

    (3) a note held by an individual who at the time of death is not a citizen
       or resident of the United States will not be subject to U.S. federal
       estate tax as a result of the individual's death if, at the time of the
       individual's death:

       - the individual did not directly or indirectly, actually or
         constructively, own 10% or more of the total combined voting power of
         all classes of our stock entitled to vote; and

       - the income on the note would not have been effectively connected with
         the conduct of a trade or business by the individual in the United
         States.

    If a non-U.S. holder is engaged in a trade or business in the United States
and interest on the note is effectively connected with the conduct of this trade
or business, or if an income tax treaty applies and the non-U.S. holder
maintains a U.S. "permanent establishment" to which the interest is generally
attributable, although the non-U.S. holder is exempt from the withholding tax
discussed in the preceding paragraph (1) provided that the holder furnishes a
properly executed IRS Form W-8ECI or successor form on or before any payment
date to claim the exemption, the holder may be subject to U.S. federal income
tax on such interest on a net basis in the same manner as if it were a U.S.
holder.

    In addition, a foreign corporation that is a holder of a note may be subject
to a branch profits tax equal to 30% of its effectively connected earnings and
profits for the taxable year, subject to some adjustments, unless it qualifies
for a lower rate under an applicable income tax treaty. For this purpose,
interest on a note or gain recognized on the disposition of a note will be
included in earnings and

                                      S-45
<PAGE>
profits if the interest or gain is effectively connected with the conduct by the
foreign corporation of a trade or business in the United States.

    We will, where required, report to the holder of notes and the Internal
Revenue Service the amount of any interest paid on the notes in each calendar
year and the amounts of tax withheld, if any, with respect to such payments.
Copies of these information returns may also be made available under the
provisions of a specific treaty agreement to the tax authorities of the country
in which the non-U.S. holder resides.

    Recently finalized Treasury Regulations generally effective for payments
made after December 31, 2000 provide alternative methods for satisfying the
certification requirement described in the third bullet point of paragraph (1)
above, and require a non-U.S. holder that provides an IRS Form W-8ECI or
successor form as discussed above, as well as a non-U.S. holder claiming the
benefit of an income tax treaty, to also provide its U.S. taxpayer
identification number. The finalized Treasury Regulation generally also require,
in the case of a note held by a foreign partnership, that the certification
described in the third bullet point of paragraph (1) above be provided by the
partners and that the partnership provide certain information, including a U.S.
taxpayer identification number. A look-through rule will apply in the case of
tiered partnerships.

    Under current Treasury Regulations, backup withholding and information
reporting will not apply to payments made by us or any of our agents, in their
capacities as agents, to a non-U.S. holder of a note if the holder has provided
the required certification that it is not a United States person as set forth in
paragraph (1) above, provided that neither we nor our agent has actual knowledge
that the holder is a United States person. Payments of the proceeds from a
disposition by a non-U.S. holder of a note made to or through a foreign office
of a broker will not be subject to information reporting or backup withholding,
except that information reporting may apply to those payments if the broker is

    - a United States person,

    - a controlled foreign corporation for U.S. federal income tax purposes,

    - a foreign person 50% or more of whose gross income is effectively
      connected with a U.S. trade or business for a specified three year period,
      or

    - with respect to payments made after December 31, 2000, a foreign
      partnership, if at any time during its tax year, one or more of its
      partners are U.S. persons, as defined in Treasury Regulations, who in the
      aggregate hold more than 50% of the income or capital interest in the
      partnership or if, at any time during its tax year, the foreign
      partnership is engaged in a U.S. trade or business.

    Payments of the proceeds from a disposition by a non-U.S. holder of a note
made to or through the U.S. office of a broker are subject to information
reporting and backup withholding unless the holder or beneficial owner certifies
as to its taxpayer identification number or otherwise establishes an exemption
from information reporting and backup withholding.

    Any amounts withheld under the backup withholding rules from a payment to a
non-U.S. holder will be allowed as a refund or a credit against the holder's
U.S. federal income tax liability, provided the required information is
furnished to the Internal Revenue Service.

                                      S-46
<PAGE>
                                  UNDERWRITING

GENERAL

    Subject to the terms and conditions set forth in an underwriting agreement
among our company and each of Merrill Lynch, Pierce, Fenner & Smith
Incorporated, Credit Suisse First Boston Corporation and Salomon Smith Barney
Inc., we have agreed to sell to the underwriters, and each of the underwriters
severally and not jointly has agreed to purchase from us, the aggregate
principal amount of the notes shown below opposite its name.

<TABLE>
<CAPTION>
                                                                 PRINCIPAL
UNDERWRITERS                                                  AMOUNT OF NOTES
- ------------                                                  ---------------
<S>                                                           <C>
Merrill Lynch, Pierce, Fenner & Smith
          Incorporated......................................   $165,000,000
Credit Suisse First Boston Corporation......................     67,500,000
Salomon Smith Barney Inc....................................     67,500,000
                                                               ------------
          Total.............................................   $300,000,000
                                                               ============
</TABLE>

    The several underwriters have agreed, subject to the terms and conditions
included in the underwriting agreement, to purchase all of the notes being sold
under the agreement, if any of the notes being sold under the agreement are
purchased. In the event of a default by an underwriter, the underwriting
agreement provides that, in certain circumstances, the purchase commitments of
the nondefaulting underwriters may be increased or the underwriting agreement
may be terminated.

    We have agreed to indemnify the underwriters against some liabilities,
including some liabilities under the Securities Act, or to contribute to
payments the underwriters may be required to make in respect of those
liabilities.

    The notes are being offered by the several underwriters, subject to prior
sale, when, as and if issued to and accepted by them, subject to approval of
legal matters by counsel for the underwriters and other conditions. The
underwriters reserve the right to withdraw, cancel or modify such offer and to
reject orders in whole or in part.

CONCESSIONS AND DISCOUNTS

    The underwriters have advised us that they propose initially to offer the
notes to the public at the initial public offering price set forth on the cover
page of this prospectus supplement, and to dealers at that price less the
concession not in excess of .35% of the principal amount of the notes. The
underwriters may allow, and such dealers may reallow, a discount not in excess
of .25% of the principal amount of the notes to other dealers. After the initial
public offerings, the public offering price, concessions and discounts may be
changed.

    The expenses of the offering, exclusive of the underwriting discount, are
estimated at approximately $450,000 and are payable by us.

NEW ISSUE OF NOTES

    The notes are a new issue of securities with no established trading market.
We do not intend to apply for listing of the notes on any national securities
exchange or for quotation of the notes on any automated dealer quotation system.
We have been advised by the underwriters that they presently intend to make a
market in the notes after the consummation of the offering contemplated hereby,
although they are under no obligation to do so and may discontinue any
market-making activities at any time without any notice. No assurance can be
given as to the liquidity of the trading market for the

                                      S-47
<PAGE>
notes or that an active public market for the notes will develop. If an active
public trading market for the notes does not develop, the market price and
liquidity of the notes may be adversely affected.

PRICE STABILIZATION AND SHORT POSITIONS

    In connection with the offering, the underwriters are permitted to engage in
transactions that stabilize the market price of the notes. These transactions
consist of bids or purchases for the purpose of pegging, fixing or maintaining
the price of the notes. If the underwriters create a short position in the notes
in connection with the offering, i.e., if they sell more notes than are set
forth on the cover page of this prospectus supplement, the underwriters may
reduce that short position by purchasing notes in the open market. In general,
purchases of a security for the purpose of stabilization or to reduce a short
position could cause the price of the security to be higher than it might be in
the absence of such purchases.

    Neither our company nor any of the underwriters makes any representation or
prediction as to the direction or magnitude of any effect that the transactions
described above may have on the price of the notes. In addition, neither our
company nor any of the underwriters makes any representation that the
underwriters will engage in such transactions or that such transactions, once
commenced, will not be discontinued without notice.

OTHER RELATIONSHIPS

    Some of the underwriters and their affiliates engage in transactions with,
and perform services for, our company in the ordinary course of business and
have engaged, and may in the future engage, in commercial banking and investment
banking transactions with our company, for which they have received customary
compensation. Merrill Lynch served as an advisor in connection with our merger
with Nevada Power Company and our acquisition of Portland General Electric
Company.

                                 LEGAL MATTERS

    Legal matters regarding the validity of the notes offered under this
prospectus supplement will be passed upon on our behalf by Choate, Hall &
Stewart (a partnership including professional corporations), Boston,
Massachusetts. Legal matters relating to the offering will be passed upon for
the underwriters by Thelen Reid & Priest LLP. Choate, Hall & Stewart and Thelen
Reid & Priest LLP will rely on the opinion of Woodburn and Wedge, Reno, Nevada,
as to matters of Nevada law. Thelen Reid & Priest LLP represents Sierra Pacific
Resources and its utility subsidiaries in connection with certain federal tax
matters.

                                    EXPERTS

    The consolidated financial statements of Sierra Pacific Resources, the
financial statements of Nevada Power Company, the consolidated financial
statements of Sierra Pacific Power Company and the related financial statement
schedules incorporated in this prospectus supplement and accompanying prospectus
by reference from Sierra Pacific Resources', Nevada Power Company's and Sierra
Pacific Power Company's Annual Reports on Form 10-K for the year ended
December 31, 1999 have been audited by Deloitte & Touche LLP, independent
auditors, as stated in their reports, which are incorporated herein by
reference, and have been so incorporated in reliance upon the reports of such
firm given upon their authority as experts in accounting and auditing.

                      WHERE YOU CAN FIND MORE INFORMATION

    We file reports, proxy statements and other information with the SEC. Our
SEC filings are also available over the Internet at the SEC's web site at
http://www.sec.gov. You may also read and copy any document we file by visiting
the SEC's public reference rooms in Washington, D.C., New York, New

                                      S-48
<PAGE>
York, and Chicago, Illinois. Please call the SEC at 1-800-SEC-0330 for further
information about the public reference rooms. You may also inspect our SEC
reports and other information at the New York Stock Exchange, Inc., 20 Broad
Street, New York, New York 10005.

    We have filed a registration statement on Form S-3 with the SEC covering the
securities. For further information on our company and the notes, you should
refer to our registration statement and its exhibits. This prospectus supplement
and the accompanying prospectus summarize material provisions of contracts and
other documents that we refer you to. Because the prospectus supplement and
prospectus may not contain all the information that you may find important, you
should review the full text of these documents. We have included copies of these
documents as exhibits to our registration statement.

               INCORPORATION OF INFORMATION WE FILE WITH THE SEC

    The SEC allows us to incorporate by reference the information we file with
them, which means:

    - incorporated documents are considered part of this prospectus supplement
      and the accompanying prospectus;

    - we can disclose important information to you by referring you to those
      documents; and

    - information that we file with the SEC will automatically update and
      supersede this incorporated information.

    We incorporate by reference the documents listed below which were filed with
the SEC under the Exchange Act:

    - our annual report on Form 10-K for the year ended December 31, 1999, which
      is combined with the annual report on Form 10-K for Nevada Power;

    - Sierra Pacific Power's annual report on Form 10-K for the year ended
      December 31, 1999;

    - our current report on Form 8-K dated August 8, 1999 and the 8-K/A
      amendment thereto dated September 20, 1999;

    - our current report on Form 8-K dated April 14, 2000;

    - our current report on Form 8-K dated April 21, 2000; and

    - our current report on Form 8-K dated May 5, 2000.

    We also incorporate by reference each of the following documents that we
will file with the SEC after the date of this prospectus supplement until this
offering is completed:

    - reports filed under Sections 13(a) and (c) of the Exchange Act;

    - definitive proxy or information statements filed under Section 14 of the
      Exchange Act in connection with any subsequent stockholders' meeting; and

    - any reports filed under Section 15(d) of the Exchange Act.

    You should rely only on information contained or incorporated by reference
in this prospectus supplement and accompanying prospectus. We have not
authorized any other person to provide you with different information. If anyone
provides you with different or inconsistent information, you should not rely on
it. We are not making an offer to sell these securities in any jurisdiction
where the offer or sale is not permitted.

    You should assume that the information appearing in this prospectus
supplement is accurate as of the date of this supplement only. Our business,
financial condition and results of operations may have changed since that date.

    You may request a copy of any filings referred to above (excluding
exhibits), at no cost, by contacting us at the following address: Assistant
Treasurer, Sierra Pacific Resources, P.O. Box 30150 (6100 Neil Road), Reno
Nevada 89520-3150, Telephone: (775) 834-4358.

                                      S-49
<PAGE>
P_R_O_S_P_E_C_T_U_S

                                     [LOGO]

                    SIERRA PACIFIC RESOURCES CAPITAL TRUST I
                   SIERRA PACIFIC RESOURCES CAPITAL TRUST II

    By this prospectus, we may offer from time to time up to $500,000,000 of
our:

                                DEBT SECURITIES
        PREFERRED SECURITIES OF SIERRA PACIFIC RESOURCES CAPITAL TRUST I
       PREFERRED SECURITIES OF SIERRA PACIFIC RESOURCES CAPITAL TRUST II

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

    Sierra Pacific Resources is a Nevada corporation. Sierra Pacific Resources
Capital Trust I and Sierra Pacific Resources Capital Trust II are Delaware
business trusts. Sierra Pacific Resources is the sponsor of Sierra Pacific
Resources Capital Trust I and Sierra Pacific Resources Capital Trust II.

    When we offer securities, we will provide you with a prospectus supplement
or a term sheet describing the terms of the specific issue of securities
including the offering price of the securities.

    You should read this prospectus and the prospectus supplement or the term
sheet relating to the specific issue of securities carefully before you invest.

    Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

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

                  The date of this prospectus is May 3, 2000.
<PAGE>
                            SIERRA PACIFIC RESOURCES

    Sierra Pacific Resources engages primarily in the energy business through
several subsidiaries. Our two largest subsidiaries, Nevada Power Company and
Sierra Pacific Power Company, are regulated public utilities. Nevada Power
Company provides electricity to the City of Las Vegas and the surrounding area
in southern Nevada. Sierra Pacific Power Company provides electricity to
western, central and northeastern Nevada, including the cities of Reno, Sparks,
Carson City and Elko, and to the Lake Tahoe area of California. Sierra Pacific
Power Company also provides natural gas and water services to the cities of Reno
and Sparks and surrounding areas. Sierra Pacific Resources and Nevada Power
Company merged in June 1999 and Nevada Power Company became a subsidiary of
Sierra Pacific Resources. As part of the merger, Sierra Pacific Power Company
and Nevada Power Company agreed to sell their electric generating assets.

    Additional information regarding the merger is contained in the documents
incorporated by reference into this prospectus. See "Incorporation of
Information We File With the SEC" on p. 30.

    The principal executive office of Sierra Pacific Resources is P.O. Box
301500 (6100 Neil Road), Reno, Nevada 89520-3150, and the telephone number is
(775) 834-4011.

    In this prospectus, "Sierra Pacific," "we," "us" and "our" refer
specifically to Sierra Pacific Resources, the holding company.

                                   THE TRUSTS

    Sierra Pacific Capital Trust I and Sierra Pacific Capital Trust II are
statutory business trusts created under Delaware law. They were created pursuant
to declarations of trust and by the filing of a Certificate of Trust with the
Secretary of State of the State of Delaware on June 7, 1999. Each declaration of
trust will be amended and restated in its entirety substantially in the forms
filed as an exhibit to the registration statement of which this prospectus is a
part. Each declaration will be qualified as an indenture under the Trust
Indenture Act of 1939, as amended. When the preferred securities of each trust
are issued, the purchasers of those securities will own all of the preferred
securities of each trust. See "Description of the Preferred Securities." We will
directly or indirectly acquire all of the trusts' issued and outstanding common
securities, which will be in an aggregate liquidation amount equal to at least
3% of the total capital of each trust. The trusts will use all of the proceeds
from the issuance of their preferred securities and common securities
(collectively, the "Trust Securities") to purchase subordinated debt securities
issued by Sierra Pacific. The only assets of each trust are subordinated debt
securities issued by Sierra Pacific. Each trust exists for the exclusive
purposes of

    - issuing its Trust Securities representing undivided beneficial interests
      in the assets of the trust;

    - investing the gross proceeds of the sale of its Trust Securities in
      subordinated debt securities issued by Sierra Pacific; and

    - engaging in only those other activities necessary or incidental to the
      foregoing purposes.

    Each trust has a term of approximately 55 years, but may be dissolved
earlier as provided in its declaration.

    Sierra Pacific has appointed the following four trustees to conduct each
trust's business and affairs:

    - two officers of Sierra Pacific (the "administrative trustees");

    - The Bank of New York (the "property trustee"); and

    - The Bank of New York (Delaware) (the "Delaware trustee").

                                       1
<PAGE>
    The property trustee will hold title to the subordinated debt securities of
Sierra Pacific purchased by each trust for the benefit of each trust and the
holders of the Trust Securities. As long as the subordinated debt securities are
held by a trust, the property trustee will have the power to exercise all
rights, powers, and privileges of a holder of subordinated debt securities under
the indenture to be entered into by and between Sierra Pacific and The Bank of
New York, as indenture trustee. In addition, the property trustee will maintain
exclusive control of a segregated non-interest bearing bank account for each
trust (the "property trustee accounts") to hold all payments made in respect of
the subordinated debt securities for the benefit of the holders of the Trust
Securities of each trust.

    Sierra Pacific, as the holder of all the common securities of each trust,
will have the right to appoint, remove or replace any trustee (subject to the
limitations shown in the declarations) and to increase or decrease the number of
trustees of each trust, provided that the number of trustees of each trust shall
be at least three. Sierra Pacific will pay all fees, expenses, debts and
obligations (other than with respect to the Trust Securities) related to each
trust and the offering of the Trust Securities by each trust.

    The rights of the holders of the preferred securities of each trust,
including economic rights, rights to information and voting rights, are
contained in its declaration and in the Delaware Business Trust Act. See
"Description of the Preferred Securities of the Trusts." The declarations also
incorporate by reference the terms of the Trust Indenture Act.

    The principal executive office of each trust is P.O. Box 30150 (6100 Neil
Road), Reno, Nevada 89520-3150. The telephone number of each trust is
(775) 834-4001.

                                USE OF PROCEEDS

    We intend to use the net proceeds from the sale of our debt securities for
general corporate purposes, unless otherwise specified in the prospectus
supplement relating to a specific issue of debt securities. General corporate
purposes may include financing the activities of Sierra Pacific's utility or
non-utility subsidiaries, financing our assets, refinancing our existing
borrowings, and financing acquisitions. Until we use the net proceeds from the
sale of any of our securities for general corporate purposes, we will use the
net proceeds to reduce our short-term indebtedness or for temporary investments.
We expect that we will, on a recurrent basis, engage in additional financings as
the need arises to finance our growth, through acquisitions or otherwise, or to
refinance our existing borrowings.

    We currently intend to use the net proceeds from the sale of our debt
securities to cover a portion of the cash consideration required in connection
with our merger with Nevada Power Company and to repay bank indebtedness
incurred in connection with the Merger. The specific allocations of the proceeds
we receive from the sale of our securities will be described in the prospectus
supplement relating thereto.

    Each trust will use all proceeds received from the sale of its Trust
Securities and common securities to purchase subordinated debt securities issued
by us.

                                       2
<PAGE>
    CONSOLIDATED RATIOS OF EARNINGS TO FIXED CHARGES AND PREFERRED DIVIDENDS

    The following table shows our consolidated ratios of earnings to fixed
charges and preferred dividends. The ratios shown in the table are both the
historical ratios and the pro forma combined ratio showing the effect of the
merger between Sierra Pacific Resources and Nevada Power Company. As a result of
the merger between Sierra Pacific Resources and Nevada Power Company, which has
been treated for accounting purposes as a reverse acquisition with Nevada Power
Company being the acquiror, the historical ratios are those of Nevada Power
Company. The pro forma ratio assumes that the merger occurred at the beginning
of the applicable period.

<TABLE>
<CAPTION>
                                                1999                    YEAR ENDED DECEMBER 31,
                                             (COMBINED    ----------------------------------------------------
                                             PRO FORMA)     1999       1998       1997       1996       1995
                                             ----------   --------   --------   --------   --------   --------
<S>                                          <C>          <C>        <C>        <C>        <C>        <C>
Consolidated ratio of earnings
  to fixed charges and preferred
  dividends................................     1.68        1.62       2.48       2.70       2.64       2.60
</TABLE>

    For the purpose of calculating the consolidated ratio of earnings to fixed
charges and preferred dividends, "fixed charges" represent the aggregate of
interest charges on short-term and long-term debt and distributions on preferred
securities of consolidated subsidiaries, allowance for borrowed funds used
during construction (AFUDC) and capitalized interest, the interest portion of
rental expense deemed to be attributable to interest, and the pre-tax preference
security dividend requirements of consolidated subsidiaries. "Earnings"
represent the aggregate of income before obligated mandatorily redeemable
preferred securities, income taxes, and fixed charges, less AFUDC and
capitalized interest, and pre-tax preference security dividend requirements of
consolidated subsidiaries.

                       DESCRIPTION OF THE DEBT SECURITIES

GENERAL

    From time to time we may issue debt securities in one or more series as
either senior securities ("senior debt securities") or subordinated securities
("subordinated debt securities"). The term "debt securities" refers to both the
senior debt securities and the subordinated debt securities.

    Senior debt securities will be issued under an indenture, as supplemented
from time to time (the "senior indenture"), between Sierra Pacific and The Bank
of New York, as trustee (the "senior indenture trustee"). Unless specified in a
prospectus supplement, subordinated debt securities will be issued under an
indenture, as supplemented from time to time (the "subordinated indenture"),
between Sierra Pacific and The Bank of New York, as trustee (the "subordinated
indenture trustee"). The term "indentures" refers to the senior indenture and
the subordinated indenture. Each of the indentures will be subject to and
governed by the Trust Indenture Act of 1939.

    Below is a description of the general terms of the debt securities. The
particular terms of a series of debt securities will be described in a
prospectus supplement. The following summary of the material terms and
provisions of the debt securities is not complete and is subject to, and
qualified in its entirety by reference to, the relevant indentures, copies of
which are filed as exhibits to the registration statement of which this
prospectus is a part.

    The indentures do not limit the amount of debt securities that we may issue,
nor do they limit us or our subsidiaries from issuing any other unsecured debt.

    The senior debt securities will rank equally with all of our unsecured and
unsubordinated debt. The subordinated debt securities will be unsecured and will
be subordinate and junior in priority of payment to our other indebtedness to
the extent described in a prospectus supplement. As a holding company, our cash
flows and our ability to service our debt are dependent on the cash flows of our
subsidiaries. Our subsidiaries are separate and distinct legal entities and will
have no obligation to pay

                                       3
<PAGE>
any amounts due under the debt securities. In addition, our two largest
subsidiaries, Nevada Power and Sierra Pacific Power, are subject to regulation
by state utility commissions which may impose limitations on the rate of return
on equity or otherwise impact the amount of dividends which may be paid by those
companies. Moreover, the articles of incorporation of Sierra Pacific Power
Company contain restrictions on the payment of dividends on that subsidiary's
common stock if there is currently a default in the payment of dividends on the
company's preferred stock. Similarly, the terms of certain outstanding series of
first mortgage bonds of both Nevada Power Company and Sierra Pacific Power
Company contain limits on the amount of dividends that may be paid on that
company's common stock. Finally, the terms of the bank credit facilities of
Nevada Power Company and Sierra Pacific Power Company prohibit the payment of
dividends on each company's common stock if that company is in default under its
credit facility. As a result, the debt securities will be effectively
subordinated to all indebtedness and other liabilities of our subsidiaries.

TERMS OF THE DEBT SECURITIES

    Each prospectus supplement will describe the terms of a series of debt
securities, including:

    - the title and series designation;

    - the aggregate principal amount and authorized denominations of the debt
      securities;

    - the percentage of principal amount at which the debt securities will be
      issued;

    - the stated maturity date;

    - any fixed or variable interest rate or rates per annum;

    - the times at which any interest will be payable, the date or dates from
      which interest will accrue and the regular record dates for interest
      payments or the method for determining those dates, and any right to defer
      interest payments on the debt securities of a series;

    - the principal amount payable, whether at maturity or upon earlier
      acceleration, and whether the principal amount will be determined with
      reference to an index, formula or other method;

    - whether the debt securities are denominated or payable in United States
      dollars;

    - any sinking fund requirements;

    - any terms under which Sierra Pacific can redeem the debt securities;

    - any terms for repayment of principal amount at the option of the holder;

    - whether and under what circumstances Sierra Pacific will pay additional
      amounts ("Additional Amounts") under any debt securities to a person who
      is not a U.S. person for specified taxes, assessments or other
      governmental charges and whether Sierra Pacific has the option to redeem
      the affected debt securities rather than pay any Additional Amounts;

    - the form in which Sierra Pacific will issue the debt securities, whether
      registered, bearer or both, and any restrictions applicable to the
      exchange of one form for another and to the offer, sale and delivery of
      the debt securities in either form;

    - whether the debt securities will be issued in global form, and any terms
      and conditions under which interests the debt securities in global form
      may be exchanged for individual debt securities;

    - the minimum denominations;

    - the defeasance provisions, if any, that apply to the debt securities
      (other than those described herein);

                                       4
<PAGE>
    - the person to whom any interest on a registered security is payable, if
      that person is not the registered owner of the debt securities, or the
      manner in which any interest is payable on a bearer security if other than
      upon presentation of the coupons pertaining thereto, as the case may be;

    - the terms and conditions upon which the debt securities may be convertible
      into shares of common stock or other securities of Sierra Pacific,
      including conversion price, conversion period and other conversion
      provisions;

    - any events of default or covenants not contained in the applicable
      indenture; and

    - any other specific terms of the debt securities which are not inconsistent
      with the provisions of the applicable indenture.

    Prospective purchasers of debt securities should be aware that special U.S.
Federal income tax, accounting and other considerations may be applicable to
instruments such as the debt securities. The prospectus supplement relating to
an issue of debt securities will describe these considerations, if applicable.

    The provisions of the indentures permit Sierra Pacific, without the consent
of holders of any debt securities, to issue additional debt securities with
terms different from those of debt securities previously issued and to reopen a
previous issue of a series of debt securities and issue additional debt
securities of that series.

    Sierra Pacific will pay or deliver principal and any premium, Additional
Amounts, and interest in the manner, at the places and subject to the
restrictions described in the applicable indenture, the debt securities and the
applicable prospectus supplement.

CONSOLIDATION, MERGER OR SALE

    The indentures permit Sierra Pacific to merge or consolidate, sell, lease,
for a term extending beyond the last stated maturity of debt securities
outstanding under the indentures, or convey all or substantially all of its
assets, if the following conditions are satisfied:

    - no event of default would occur under the indentures as a result of such
      transaction;

    - any successor or acquiror assumes all of the obligations of Sierra Pacific
      under the indentures and the debt securities; and

    - the successor or acquiror is organized and existing under the laws of the
      United States of America or of any U.S. state.

    The indentures do not prevent or restrict any of the following:

    - consolidation or merger where after the consummation of which Sierra
      Pacific would be the surviving entity, or any conveyance or transfer or
      lease of any part of the properties of Sierra Pacific which does not
      constitute the entirety or substantially the entirety of these properties;
      or

    - the approval by Sierra Pacific of or consent by Sierra Pacific to, any
      consolidation or merger to which any "restricted subsidiary," or any other
      subsidiary or affiliate of Sierra Pacific, may be a party, or any
      conveyance, transfer or lease by any subsidiary or affiliate of Sierra
      Pacific of any of its assets.

    If a series of subordinated debt securities is held by a trust, any
transaction referred to above would also have to be permitted under and not
result in any breach of violation of the applicable trust agreement and
guarantee.

                                       5
<PAGE>
MODIFICATION OF INDENTURES; WAIVER

    Each indenture may be modified or amended by Sierra Pacific and the
applicable trustee without the consent of any holders with respect to matters
specified in the indenture, including but not limited to:

    - to cure any ambiguity or correct any inconsistency in the indenture;

    - to provide for uncertificated debt securities;

    - to establish the form or terms of debt securities of any series; or

    - to make any change that does not materially adversely affect the rights of
      any holder of a debt security.

    In addition, under each indenture, Sierra Pacific and the applicable trustee
may change the rights of holders of a series of debt securities with the written
consent of the holders of at least a majority in aggregate principal amount of
the outstanding debt securities of each affected series. However, the following
changes may be made only with the consent of each holder of any outstanding debt
securities affected:

    - extension of the stated maturity of those debt securities;

    - reduction of the principal amount, reduction of the rate or rates of or
      extension of the time of payment of interest;

    - change in the place or currency of any payment of principal or interest;

    - impairment of the right to bring a suit for the enforcement of any payment
      on or with respect to those debt securities;

    - waiver of a default in the payment of the principal of or interest on
      those debt securities;

    - modification in any manner adverse to the holders of those debt securities
      of the terms and conditions of the obligations of Sierra Pacific; and

    - modification of any of the foregoing requirements or reduction of the
      percentage of holders of debt securities required to consent to any
      amendment or waiver of any covenant or past default.

    If a series of subordinated debt securities is held by a trust, no
modification of the subordinated indenture may occur without the prior consent
of the holders of at least a majority of the aggregate liquidation preference of
the trust's preferred securities.

EVENTS OF DEFAULT

    Each of the following will be an Event of Default with respect to each
series of debt securities issued under each indenture:

    - default in the payment of any principal, when due (except when the failure
      to make payment when due results from mistake, oversight or transfer
      difficulties and does not continue for more than three business days);

    - default in the payment of interest or Additional Amounts and the
      continuance of that default for a period of 30 days;

    - default with respect to any obligation to make payments to a sinking fund,
      when due (except when the failure to make payment when due results from
      mistake, oversight or transfer difficulties and does not continue for more
      than three business days);

                                       6
<PAGE>
    - default in the performance or breach of any other covenant or warranty
      contained in the applicable indenture or in the debt securities with
      respect to that series and continuance of the default for a period of
      60 days after written notice as provided in the applicable indenture;

    - specified events of involuntary bankruptcy, insolvency or reorganization
      of Sierra Pacific which remain in effect for a period of sixty consecutive
      days;

    - commencement by Sierra Pacific of a voluntary case in bankruptcy or any
      general assignment to creditors; or

    - any other Event of Default provided in the applicable prospectus
      supplement.

    If a series of subordinated debt securities is held by a trust, it would
also be an event of default if the trust dissolves, winds up or terminates,
except in connection with:

    - the distribution of the subordinated debt securities to holders of
      preferred and common securities of the trust;

    - the redemption of all of the preferred and common securities of the trust;
      or

    - mergers, consolidations, conversions or amalgamations permitted by the
      declaration of trust.

REMEDIES

    ACCELERATION OF MATURITY

    If an Event of Default with respect to debt securities of any series occurs
and is continuing, the applicable trustee or the holders of at least 25% in
principal amount of the outstanding debt securities of that series may declare
all amounts due and payable or deliverable immediately. Holders of a majority in
principal amount of the outstanding debt securities of an affected series may
rescind and annul a declaration of acceleration if Sierra Pacific deposits with
the trustee enough money to cover all overdue amounts on the outstanding debt
securities other than the amounts that would be due as a result of the
acceleration.

    WAIVER OF DEFAULT

    Holders of a majority in principal amount of the outstanding debt securities
of an affected series (or if subordinated debt securities of an affected series
are held by a trust, the holders of at least a majority in liquidation amount of
the trust's preferred securities) may waive any past default or event of default
of that series, except defaults or events of default regarding covenants that
cannot be modified or amended without the consent of each holder of any
outstanding debt securities affected (see "--Modification of Indentures; Waiver"
above).

    RIGHT TO DIRECT PROCEEDINGS; LIMITATIONS

    Holders of debt securities may not enforce the applicable indentures or the
relevant debt securities except as set forth in the applicable indenture. The
trustee under an indenture may refuse to enforce the indenture on the applicable
debt securities unless it receives indemnification satisfactory to it. Subject
to limitations contained in the indentures, holders of a majority in principal
amount of debt securities issued under an indenture may direct the time, method
and place of conducting any proceeding for any remedy available to the trustee
under the applicable indenture or of exercising trust or power conferred on the
trustee; provided, however, that (a) such direction does not conflict with any
rule of law or with the applicable indenture, and could not involve the trustee
in personal liability in circumstances where indemnity would not, in the
trustee's sole discretion, be adequate, (b) the trustee determines that such
direction does not unduly prejudice the rights of the holders of all series of
debt

                                       7
<PAGE>
securities not joining in the giving of the applicable direction and (c) the
trustee may take any other action deemed proper by the trustee which is not
inconsistent with such direction.

    If the subordinated debt securities of any series are held by a trust, and a
"declaration event of default" (as defined under "Description of Preferred
Securities of the Trusts--Declaration Events of Default") has occurred and is
attributable to the failure of Sierra Pacific to pay principal, premium, if any,
or interest on, those subordinated debt securities, then each holder of the
preferred securities of that trust may sue Sierra Pacific, or seek other
remedies to force payment to that holder of an amount equal to the aggregate
liquidation amount of the preferred securities held by that holder.

    NO IMPAIRMENT OF RIGHT TO RECEIVE PAYMENT

    Notwithstanding any other provision in the indentures, (including remedies
which are subject to conditions precedent), each holder of debt securities will
have the right, which is absolute and unconditional, to receive payment of the
principal of and premium, if any, and interest, if any, on the holder's debt
securities, when due and to institute suit for the enforcement of payment. Such
rights may not be impaired or affected without the consent of such holder.

    NOTICE OF DEFAULT

    If any event of default occurs under an indenture and is continuing and if
it is known to the trustee, the trustee shall mail to each holder of debt
securities issued under that indenture notice of the event of default, within 90
days after it occurs. The Trust Indenture Act currently permits the trustee to
withold notices of default (except for certain payment defaults) if the trustee
in good faith determines that withholding the notice is in the interest of the
holders of the debt securities.

SPECIAL TERMS RELATING TO THE SUBORDINATED DEBT SECURITIES TO BE HELD BY TRUSTS

    SUBORDINATION

    If Sierra Pacific's assets are distributed upon dissolution, winding up,
liquidation or reorganization, payments on subordinated debt securities will be
subordinated, to the extent provided in the subordinated indenture, to the prior
payment in full of all senior indebtedness, including senior debt securities. If
the maturity of any subordinated debt securities is accelerated, the holders of
all senior indebtedness outstanding at the time of acceleration will be entitled
to receive payment in full of all amounts due on the senior indebtedness before
the holders of subordinated debt securities will be entitled to receive or
retain any payment on the subordinated debt securities. However, the obligation
of Sierra Pacific to make payments on the subordinated debt securities will not
be affected in any other manner. Sierra Pacific may not make any payment on
subordinated debt securities at any time when there is a default in the payment
or delivery of any amounts due on any senior indebtedness, including payment of
any sinking fund. If, while there is a default on senior indebtedness, any
payment is received by the subordinated indenture trustee under the subordinated
indenture or the holders of any subordinated debt securities before all senior
indebtedness has been paid in full, that payment or distribution must be paid
over to the holders of the unpaid senior indebtedness or applied to the
repayment of the unpaid senior indebtedness. Holders of subordinated debt
securities will be subrogated to the rights of the holders of senior
indebtedness to the extent of payments made on senior indebtedness upon any
distribution of assets in any proceeding in respect of subordinated debt
securities.

    REDEMPTION

    Unless otherwise indicated in the applicable prospectus supplement,
subordinated debt securities will not be subject to any sinking fund.

                                       8
<PAGE>
    Unless otherwise indicated in the applicable prospectus supplement, Sierra
Pacific may, at its option, redeem the subordinated debt securities of any
series in whole at any time or in part from time to time. Except as otherwise
specified in the applicable prospectus supplement, the redemption price will be
equal to the principal and any accrued and unpaid interest on the subordinated
debt securities to the redemption date.

    Except as otherwise specified in the applicable prospectus supplement, if a
subordinated debt security tax event (as defined below) shall occur and be
continuing, Sierra Pacific may, at its option, redeem the subordinated debt
securities in whole at any time within 90 days of the occurrence of the
Subordinated Debt Security Tax Event, at a redemption price equal to 100% of the
principal amount of the subordinated debt securities then outstanding plus
accrued and unpaid interest to the date fixed for redemption.

    "Subordinated Debt Security Tax Event" means the receipt by Sierra Pacific
of an opinion of counsel experienced in such matters to the effect that:

    - as a result of any amendment to, or change (including any announced
      prospective change) in, the laws (or any regulations thereunder) of the
      United States or any political subdivision or taxing authority thereof or
      therein, or

    - as a result of any official administrative pronouncement or judicial
      decision interpreting or applying the laws or regulations, which amendment
      or change is effective or which pronouncement or decision is announced on
      or after the date of issuance of the applicable series of subordinated
      debt securities, there is more than an insubstantial risk that interest
      payable by Sierra Pacific on the series of subordinated debt securities is
      not, or within 90 days of the date of the opinion will not be, deductible
      by Sierra Pacific, in whole or in part, for United States Federal income
      tax purposes.

    Notice of any redemption will be mailed at least 30 days but not more than
60 days before the redemption date to each holder of subordinated debt
securities to be redeemed at its registered address. Unless Sierra Pacific
defaults in payment of the redemption price, on and after the redemption date
interest ceases to accrue on the subordinated debt securities or portions
thereof called for redemption.

    If this prospectus is being delivered with the offering of a series of
subordinated debt securities, the accompanying prospectus supplement will show
the approximate amount of senior indebtedness outstanding as of a recent date.

    OPTION TO EXTEND INTEREST PAYMENT DATE

    If provided in the applicable prospectus supplement, Sierra Pacific will
have the right at any time and from time to time during the term of any
subordinated debt securities to defer payment of interest for the number of
consecutive interest payment periods as may be specified in the applicable
prospective supplement. No extension period may extend beyond the stated
maturity date of subordinated debt securities. United States federal income tax
consequences and special considerations applicable to the extension of interest
payment dates will be described in the applicable prospectus supplement.

    RESTRICTIONS ON CERTAIN PAYMENTS

    Unless otherwise specified in the applicable Prospectus Supplement, Sierra
Pacific will covenant, as to each series of subordinated debt securities, that
it will not, and will not permit any of its subsidiaries to:

    - declare or pay any dividends or distributions on, or redeem, purchase,
      acquire, or make a liquidation payment with respect to, any of Sierra
      Pacific's capital stock, or

                                       9
<PAGE>
    - make any payment of principal, interest or premium, if any, on or repay,
      repurchase or redeem any debt securities of Sierra Pacific (including
      other subordinated debt securities) that rank PARI PASSU with or junior in
      interest to the subordinated debt securities of any subsidiary or any
      guarantee payments with respect to any guarantee by Sierra Pacific of the
      debt securities of any subsidiary, if such guarantee ranks PARI PASSU or
      junior in interest to the subordinated debt securities;

if at that time:

    - there shall have occurred any event which Sierra Pacific has actual
      knowledge that with the giving of notice or the lapse of time, or both
      would cause an Event of Default under the subordinated indenture;

    - there is a default by Sierra Pacific relating to its payment of any
      obligations under a preferred securities guarantee; or

    - Sierra Pacific shall have given notice of its selection of an extension
      period under the subordinated indenture and shall not have rescinded the
      notice, or the extention period shall be continuing.

    The above covenants do not restrict the payment of dividends by Sierra
Pacific Power Company or Nevada Power Company on their capital stock, nor do
they restrict Sierra Pacific from paying:

    - dividends or distributions in common stock,

    - redemptions or purchases of any rights pursuant to any rights plan adopted
      by Sierra Pacific, or any successor to the rights plan, and the
      declaration of a dividend of the rights or the issuance of stock under the
      plan in the future,

    - payments under any guarantee, and

    - purchases of common stock related to the issuance of common stock under
      any of Sierra Pacific's benefit plans for its directors, officers or
      employees or under Sierra Pacific's Common Stock Investment Plan or any
      successor plan.

    OPTION TO CHANGE STATED MATURITY DATE

    If provided in the applicable prospectus supplement, Sierra Pacific shall
have the right to:

    - change the maturity date of a series of subordinated debt securities and
      exchange those subordinated debt securities for preferred securities of
      the trust upon liquidation of the trust; or

    - extend the stated maturity of the subordinated debt securities;

provided that at the time of any change in the maturity date:

    - Sierra Pacific is not in bankruptcy, insolvent or in liquidation;

    - Sierra Pacific is not in default on the principal or interest on the
      subordinated debt securities;

    - the applicable trust is not in arrears on payments of distributions on its
      preferred securities;

    - the subordinated debt securities are rated not less than BBB--by
      Standard & Poor's Rating Services on Baa3 by Moody's Investors
      Service, Inc.; and

    - the extended maturity date is no later than the 49th anniversary of the
      initial issuance of the preferred securities of the applicable trust.

    In addition, if Sierra Pacific exercises its right to liquidate the trust
and exchange subordinated debt securities for preferred securities of the trust,
any changed stated maturity date cannot be earlier than five years after the
issuance of the preferred securities and no later than thirty years after the
issuance of the preferred securities.

                                       10
<PAGE>
SPECIAL TERMS RELATING TO THE SENIOR DEBT SECURITIES

    LIMITATIONS UPON LIENS ON STOCK OF RESTRICTED SUBSIDIARIES

    Sierra Pacific will not, nor will it permit any "restricted subsidiary" to,
create, issue, assume, guarantee or permit to exist any indebtedness for
borrowed money secured by a mortgage, security interest, pledge, lien or other
encumbrance upon any shares of stock of any restricted subsidiary without
effectively providing that the senior debt securities shall be secured equally
and ratably with the indebtedness.

    The term "restricted subsidiary" is defined in the senior indenture as any
operating subsidiary of Sierra Pacific that accounts for 10% or more of the
consolidated revenues and/or assets of Sierra Pacific.

    LIMITATIONS ON THE ISSUANCE OR DISPOSITION OF STOCK OF RESTRICTED
     SUBSIDIARIES

    Sierra Pacific will not, nor will it permit any restricted subsidiary to,
issue, sell, assign, transfer or otherwise dispose of, directly or indirectly,
any "capital stock" (other than nonvoting preferred stock) of any restricted
subsidiary, except for:

    - the purpose of qualifying directors;

    - sales or other dispositions to Sierra Pacific or one or more restricted
      subsidiaries;

    - the disposition of all or any part of the capital stock of any restricted
      subsidiary for consideration which is at least equal to the fair value of
      the capital stock as determined by Sierra Pacific's board of directors
      (acting in good faith); or

    - an issuance, sale, assignment, transfer or other disposition required to
      comply with an order of a court or regulatory authority of competent
      jurisdiction, other than an order issued at the request of Sierra Pacific
      or any restricted subsidiary.

    The term "capital stock" is defined in the senior indenture as any and all
shares, interests, rights to purchase, warrants, options, participations or
other equivalents of or interests in corporate stock.

DEFEASANCE

    The indentures provide Sierra Pacific with the option to discharge itself
from (a) all obligations of the debt securities of a series (except for
administrative obligations) or (b) compliance with the covenants of the
indentures. To exercise either option Sierra Pacific must irrevocably deposit in
trust with the indenture trustee money or obligations of, or guaranteed by, the
United States sufficient to pay all of the principal of (including any mandatory
redemption payments), premium, additional amounts and interest on the debt
securities on the dates the payments are due. To exercise either option, Sierra
Pacific is required to deliver to the indenture trustee an opinion of tax
counsel that the deposit and related defeasance would not cause the holders of
the debt securities to recognize income, gain or loss for Federal income tax
purposes. To exercise the option described in clause (a) above, the tax opinion
must be based either on a ruling of the Internal Revenue Service or a change in
the applicable Federal income tax law.

FORM, REGISTRATION, TRANSFER AND EXCHANGE

    Each series of debt securities will be issued in fully registered form
without coupons or in bearer form with or without coupon. Unless the applicable
prospectus supplement provides otherwise, registered senior debt securities will
be issued in denominations of $1,000 or integral multiples thereof and senior
debt securities issued in bearer form will be issued in the denomination of
$5,000. Unless the applicable prospectus supplement provides otherwise,
subordinated debt securities will be issuable only in registered form without
coupons in denominations of $25 and any integral multiple thereof. Each
indenture provides that debt securities may be issued in global form. If any
series of debt securities is issuable in global form, the applicable prospectus
supplement will describe the

                                       11
<PAGE>
circumstances, if any, under which beneficial owners of interests in any of
those global debt securities may exchange their interests for debt securities of
that series and of like tenor and principal amount in any authorized form and
denomination.

    Holders may present debt securities for exchange, and registered debt
securities for registration of transfer, in the manner, at the places and
subject to the restrictions set forth in the applicable indenture, the debt
securities and the applicable prospectus supplement. Holders may transfer senior
debt securities in bearer form and the coupons, if any, appertaining to the
senior debt securities will be transferrable by delivery. There will be no
service charge for any registration of transfer of registered debt securities or
exchange of debt securities, but Sierra Pacific may require payment of a sum
sufficient to cover any tax or other governmental charges that may be imposed in
connection with any registration of transfer or exchange. Bearer securities will
not be issued in exchange for registered securities.

    In the event of any redemption of debt securities of any series, Sierra
Pacific will not be required to

    - register the transfer of or exchange debt securities of that series during
      a period of 15 days next preceding the selection of securities of the
      series to be redeemed;

    - register the transfer of or exchange any registered debt security called
      for redemption, except the unredeemed portion of any registered debt
      security being redeemed in part; or

    - exchange any bearer security called for redemption except, to the extent
      provided with respect to any series of debt securities and referred to in
      the applicable prospectus supplement, to exchange the bearer security for
      a registered debt security of like tenor and principal amount that is
      immediately surrendered for redemption.

GLOBAL SECURITIES

    The debt securities of each series may be issued in whole or in part in
global form. A debt security in global form will be deposited with, or on behalf
of, a depositary, which will be named in an applicable prospectus supplement. A
global security may be issued in either registered or bearer form and in either
temporary or definitive form. A global debt security may not be transferred,
except as a whole, among the depositary for such debt security and/or its
nominees and/or successors. If any debt securities of a series are issuable as
global securities, the applicable prospectus supplement will describe any
circumstances when beneficial owners of interests in any global security may
exchange those interests for definitive debt securities of like tenor and
principal amount in any authorized form and denomination and the manner of
payment of principal and interest on any global debt security.

PAYMENT AND PAYING AGENTS

    Unless otherwise indicated in the applicable prospectus supplement, payment
of the interest on any debt securities (other than bearer securities) on any
interest payment date will be made to the person in whose name the debt
securities are registered.

    Unless otherwise indicated in the applicable prospectus supplement,
principal of and any premium, additional amounts and interest on the debt
securities (other than bearer securities) of a particular series will be payable
at the office of the paying agents designated by Sierra Pacific. Unless
otherwise indicated in the prospectus supplement, the principal corporate trust
office of the applicable trustee in The City of New York will be designated as
sole paying agent for payments with respect to debt securities of each series.

    All moneys paid by Sierra Pacific to a paying agent or the trustee for the
payment of the principal, premium additional amounts or interest on a debt
security which remains unclaimed at the end of one year will be repaid to Sierra
Pacific, and the holder of the debt security thereafter may look only to Sierra
Pacific for payment thereof.

                                       12
<PAGE>
GOVERNING LAW

    The indentures and debt securities will be governed by and construed under
the laws of the State of New York.

             DESCRIPTION OF THE PREFERRED SECURITIES OF THE TRUSTS

GENERAL

    The preferred securities of each trust will be issued under the terms of its
declaration. Each declaration will be qualified as an indenture under the Trust
Indenture Act. The property trustee of each trust, The Bank of New York, will
act as trustee for the preferred securities under each declaration for purposes
of compliance with the provisions of the Trust Indenture Act. The following
summary of the material terms and provisions of the preferred securities of each
trust is not complete and is subject to, and qualified in its entirety by
reference to, the declarations, copies of which are filed as an exhibit to the
registration statement of which this prospectus is a part, the Delaware Business
Trust Act and the Trust Indenture Act.

    Each declaration authorizes the administrative trustees of each trust to
issue its Trust Securities, which represent undivided beneficial ownership
interests in the assets of the respective trusts. The proceeds from the sale of
Trust Securities will be used by a trust to purchase a series of subordinated
debt securities issued by Sierra Pacific. The subordinated debt securities
purchased by a trust will be held by the trust's property trustee for the
benefit of the holders of its Trust Securities.

    The declarations do not permit the trusts to:

    - acquire any assets other than subordinated debt securities issued by
      Sierra Pacific;

    - issue any securities other than Trust Securities; or

    - incur any indebtedness.

    The payment of distributions out of money held by the trusts, and payments
out of money held by the trusts upon redemption of preferred securities or
liquidation of the trusts, are guaranteed by Sierra Pacific to the extent
described under "Description of Preferred Securities Guarantee."

    Each preferred securities guarantee will be held by The Bank of New York,
the guarantee trustee, for the benefit of the holders of preferred securities of
each trust. A preferred securities guarantee does not cover payment of
distributions when a trust does not have sufficient available funds to pay such
distributions.

    The prospectus supplement relating to the preferred securities of a trust
will describe the specific terms of a trust's preferred securities, including:

    - the name of the preferred securities;

    - the dollar amount and number of securities issued;

    - any provision relating to deferral of distribution payments;

    - the annual distribution rate(s), the payment date(s) and the record dates
      used to determine the holders who are to receive distributions;

    - the optional redemption provisions, if any, including the prices, time
      periods and other terms and conditions for which the preferred securities
      shall be purchased or redeemed, in whole or in part;

    - the terms and conditions, if any, upon which the applicable series of
      subordinated debt securities may be distributed to holders of the
      preferred securities;

    - the voting rights, if any, of holders of the preferred securities;

    - any securities exchange on which the preferred securities will be listed;

                                       13
<PAGE>
    - whether the preferred securities are to be issued in book-entry form and
      represented by one or more global certificates; and

    - any other relevant rights, preferences, privileges, limitations or
      restrictions of such preferred securities.

    Each prospectus supplement will describe United States Federal income tax
considerations applicable to the purchase, holding and disposition of the
preferred securities covered by that prospectus supplement.

DISTRIBUTIONS

    Distributions on the preferred securities will be cumulative, will
accumulate from the date of original issuance unless otherwise specified in the
applicable prospectus supplement and will be payable on the dates specified in
the applicable prospectus supplement. In the event that any date on which
distributions are payable on the preferred securities is not a Business Day (as
defined below), payment of the distribution payable on that date will be made on
the next succeeding day that is a Business Day. If the next succeeding day that
is a Business Day is in the next succeeding calendar year, payment of a
distribution shall be made on the immediately preceding Business Day. A
"Business Day" means any day other than a Saturday or a Sunday, or a day on
which banking institutions in The City of New York are authorized or required by
law or executive order to remain closed or a day on which the corporate trust
office of the property trustee or the subordinated indenture trustee is closed
for business.

    Distributions on the preferred securities of a trust will be made to the
extent that the trust has funds available for the payment of the distributions
in the property account. Amounts available to a trust for distribution to the
holders of its preferred securities will be limited to payments received by the
trust from Sierra Pacific with respect to subordinated debt securities from
Sierra Pacific on Sierra Pacific's guarantee on the preferred securities as
described in this prospectus.

    If provided in the applicable prospectus supplement, Sierra Pacific has the
right under the subordinated indenture to defer the payment of interest at any
time or from time to time on any series of subordinated debt securities issued
to a trust for a period which will be specified in the prospectus supplement
(each an "extension period"). No extension period may extend beyond the stated
maturity of the subordinated debt securities. As a consequence of any extension,
distributions on the preferred securities would be deferred (but would continue
to accumulate additional distributions thereon at the rate per annum shown in
the prospectus supplement) during any extension period. During an extension
period Sierra Pacific may not, and may not permit any of its subsidiaries to:

    - declare or pay any dividends or distributions on, or redeem, purchase,
      acquire or make a liquidation payment with respect to, any of its capital
      stock other than cash dividends paid by Sierra Pacific Power Company and
      Nevada Power Company to Sierra Pacific,

    - make any payment of principal, interest or premium, if any, on or repay,
      repurchase or redeem any debt securities that rank PARI PASSU with or
      junior in interest to the subordinated debt securities, or

    - make any guarantee payments with respect to any guarantee by Sierra
      Pacific of debt securities of any subsidiary of Sierra Pacific if the
      guarantee ranks PARI PASSU or junior in interest to the subordinated debt
      securities.

MANDATORY REDEMPTION

    Upon the repayment or redemption, in whole or in part, of any subordinated
debt securities issued to a trust, whether at maturity or upon earlier
redemption as provided in the subordinated indenture, the proceeds from the
repayment or redemption shall be applied by the property trustee to redeem a
like amount of the Trust Securities, upon not less than 30 nor more than
60 days notice, at a redemption price (the "redemption price") equal to the
aggregate liquidation amount of the Trust

                                       14
<PAGE>
Securities plus accumulated but unpaid distributions to the date of redemption
and the related amount of the premium, if any, paid by Sierra Pacific upon the
concurrent redemption of the subordinated debt securities. See "Description of
Debt Securities--Redemption."

    If less than all of any series of subordinated debt securities are to be
repaid or redeemed on a redemption date, then the proceeds from that repayment
or redemption shall be allocated to the redemption pro rata among the related
preferred securities and the common securities. The amount of premium, if any,
paid by Sierra Pacific upon the redemption of all or any part of any series of
subordinated debt securities to be repaid or redeemed on a redemption date shall
be allocated to the redemption pro rata among the related preferred securities
and the common securities.

    Sierra Pacific will have the right to redeem any series of subordinated debt
securities:

    - in whole at any time or in part from time to time, subject to the
      conditions described under "Description of Debt Securities--Redemption,"

    - at any time, in whole (but not in part), upon the occurrence of a Trust
      Tax Event or an Trust Investment Company Event (each as defined below), or

    - as may be otherwise specified in the applicable prospectus supplement.

TRUST SPECIAL EVENT REDEMPTION OR DISTRIBUTION

    If, at any time, a "Trust Tax Event" or a "Trust Investment Company Event"
(each as defined below, and each, a "Trust Special Event") shall occur and be
continuing, the administrative trustees of each trust shall, within 90 days
following the occurrence of the Trust Special Event elect to either:

    - dissolve the trust upon not less than 30 nor more than 60 days notice with
      the result that, after satisfaction of creditors of the trust, if any,
      subordinated debt securities held by the trust would be distributed on a
      pro rata basis to the holders of the Trust Securities in liquidation of
      the holders' interests in the trust; PROVIDED, HOWEVER, that if at the
      time there is available to the trust the opportunity to eliminate, within
      the 90-day period, the Trust Special Event by taking some ministerial
      action, such as filing a form or making an election, or pursuing some
      other similar reasonable measure which in the sole judgment of Sierra
      Pacific has or will cause no adverse effect on the trust, Sierra Pacific
      or the holders of the Trust Securities and will involve no material cost,
      the trust will pursue that measure in lieu of dissolution; or

    - cause the preferred securities of the trust to remain outstanding,
      provided that, Sierra Pacific shall pay any and all expenses incurred by
      or payable by the trust attributable to the Trust Special Event.

    Furthermore, if in the case of the occurrence of a Trust Tax Event, the
administrative trustees have received an opinion of nationally recognized
independent tax counsel experienced in these matters that there is more than an
insubstantial risk that interest payable with respect to the subordinated debt
securities issued by Sierra Pacific is not, or will not be, deductible by Sierra
Pacific for United States Federal income tax purposes even if the subordinated
debt securities were distributed to the holders of Trust Securities as described
above, then Sierra Pacific shall have the right, within 90 days following the
occurrence of the Trust Tax Event, to redeem the subordinated debt securities in
whole, but not in part, for cash upon not less than 30 nor more than 60 days
notice and promptly following any redemption, the Trust Securities will be
redeemed by the trust at the redemption price.

    "Trust Tax Event" means that Sierra Pacific shall have requested and
received and shall have delivered to the administrative trustees an opinion of
nationally recognized independent tax counsel experienced in these matters to
the effect that there has been:

    - an amendment to, change in or announced proposed change in the laws, or
      any regulations under those laws of the United States or any political
      subdivision or taxing authority of that jurisdiction,

                                       15
<PAGE>
    - a judicial decision interpreting, applying, or clarifying these laws or
      regulations,

    - an administrative pronouncement or action that represents an official
      position, including a clarification of an official position, of the
      governmental authority or regulatory body making the administrative
      pronouncement or taking any action, or

    - a threatened challenge asserted in connection with an audit of Sierra
      Pacific or the trusts, or a threatened challenge asserted in writing
      against any other taxpayer that has raised capital through the issuance of
      securities that are substantially similar to the subordinated debt
      securities or the preferred securities, which amendment or change is
      adopted or which proposed change, decision or pronouncement is announced
      or which action, clarification or challenge occurs on or after the date of
      this prospectus (collectively a "Tax Action"), which tax action relates to
      any of the items described in (1) through (3) below, and that following
      the occurrence of any Tax Action there is more than an insubstantial risk
      that:

    (1) the trusts are, or will be, subject to United States Federal income tax
       with respect to income accrued or received on the subordinated debt
       securities,

    (2) the trusts are, or will be, subject to more than a minimal amount of
       other taxes, duties or other governmental charges or

    (3) interest payable by Sierra Pacific with respect to the subordinated debt
       securities issued to the trusts is not, or will not be, deductible by
       Sierra Pacific for United States Federal income tax purposes.

    "Trust Investment Company Event" means that Sierra Pacific shall have
requested and received and shall have delivered to the administrative trustees
an opinion of nationally recognized independent legal counsel experienced in
these matters to the effect that as a result of the occurrence on or after the
date of this prospectus of a change in law or regulation or a change in
interpretation or application of law or regulation by any legislative body,
court, governmental agency or regulatory authority (a "Change in Investment
Company Act Law"), the trusts are or will be considered investment companies
which are required to be registered under the Investment Company Act.

    If subordinated debt securities are distributed to the holders of preferred
securities, Sierra Pacific will use its best efforts to cause the subordinated
debt securities to be listed on the NYSE or on any other national securities
exchange or similar organization as the preferred securities are then listed or
quoted.

    On the date fixed for any distribution of subordinated debt securities, upon
dissolution of a trust,

    - the Trust Securities of the trust will no longer be deemed to be
      outstanding, and

    - certificates representing the Trust Securities will be deemed to represent
      the subordinated debt securities having a liquidation preference equal to
      the stated liquidation amount of the Trust Securities until the
      certificates are presented to Sierra Pacific or its agent for transfer or
      reissuance.

    If a dissolution and liquidation of the trusts were to occur, subordinated
debt securities which an investor may subsequently receive on dissolution and
liquidation of the trusts may trade at a discount to the price of the preferred
securities exchanged.

REDEMPTION PROCEDURES

    The trusts may not redeem fewer than all of their outstanding preferred
securities unless all accumulated and unpaid distributions have been paid on all
of their preferred securities for all quarterly distribution periods terminating
on or before the date of redemption.

                                       16
<PAGE>
    If a trust gives a notice of redemption of its preferred securities, which
notice will be irrevocable, and if Sierra Pacific has paid to the property
trustee a sufficient amount of cash in connection with the related redemption of
the subordinated debt securities held by the trust, then, by 12:00 noon, New
York City time, on the redemption date, the trust will irrevocably deposit with
DTC funds sufficient to pay the amount payable on redemption of all book entry
certificates and will give DTC irrevocable instructions and authority to pay the
redemption amount to holders of the preferred securities. See "Book-Entry Only
Issuance--The Depository Trust Company." If notice of redemption shall have been
given and funds are deposited as required, then upon the date of deposit, all
rights of holders of any preferred securities called for redemption in this
manner will cease, except the right of the holders of those preferred securities
to receive the redemption price, without interest. In the event that any date
fixed for redemption of the preferred securities is not a Business Day, then
payment of the amount payable on that date will be made on the next succeeding
day which is a Business Day, without any interest or other payment in respect of
the amount payable subject to delay, except that, if the next succeeding day
that is a Business Day falls in the next calendar year, the payment will be made
on the immediately preceding Business Day. In the event that payment of the
redemption price in respect of the preferred securities is improperly withheld
or refused and not paid either by the trust or by Sierra Pacific under the
applicable trust guarantee described under "Description of the Preferred
Securities Guarantee," distributions on the preferred securities will continue
to accumulate from the original redemption date to the date of payment.

    In the event that fewer than all of the outstanding preferred securities are
to be redeemed, the preferred securities will be redeemed in accordance with the
procedures of DTC. See "--Book-Entry Only Issuance--The Depository Trust
Company". In the event that the Preferred Securities do not remain in book-entry
only form and fewer than all of the outstanding preferred securities are to be
redeemed, the preferred securities shall be redeemed on a pro rata basis or
pursuant to the rules of any securities exchange on which the preferred
securities are listed.

    Subject to the foregoing and applicable law, including United States Federal
securities laws, Sierra Pacific or its subsidiaries may at any time and from
time to time purchase outstanding preferred securities by tender, in the open
market or by private agreement.

LIQUIDATION DISTRIBUTION UPON DISSOLUTION

    If there is a voluntary or involuntary liquidation, dissolution, winding-up
or termination of a trust, the holders of the preferred securities of that trust
will be entitled to receive out of the assets of the trust, after satisfaction
of liabilities to creditors, distributions in cash or other immediately
available funds in an amount equal to the aggregate of the stated liquidation
amount per preferred security plus accumulated and unpaid distributions to the
date of payment, unless, in connection with the trust's liquidation,
subordinated debt securities have been distributed on a pro rata basis to the
holders of its Trust Securities.

    If, upon any trust's liquidation, the liquidation distribution can be paid
only in part because the trust has insufficient assets available to pay in full
the aggregate liquidation distribution, then the amounts payable directly by the
trust on its preferred securities shall be paid on a pro rata basis. The holders
of the common securities of the trust will be entitled to receive distributions
upon liquidation pro rata with the holders of the preferred securities, except
in the limited circumstances described below under "--Subordination of the
Common Securities".

    Each trust shall dissolve:

    - upon the bankruptcy of Sierra Pacific,

    - upon the filing of a certificate of dissolution or the equivalent with
      respect to Sierra Pacific, dissolution of the trust after having obtained
      the consent of at least a majority in liquidation

                                       17
<PAGE>
      amount of the trust's securities, voting together as a single class, or
      the revocation of Sierra Pacific's certificate of incorporation, and the
      expiration of 90 days after the date of revocation without reinstatement,

    - upon the distribution of all of the subordinated debt securities upon the
      occurrence of a Trust Special Event,

    - upon the entry of a decree of a judicial dissolution of Sierra Pacific or
      the applicable trust, or

    - upon the redemption of all the applicable Trust Securities.

SUBORDINATION OF THE COMMON SECURITIES

    Payment of amounts upon liquidation of a trust's Trust Securities shall be
made pro rata based on the liquidation amount of the Trust Securities; provided,
however, that upon:

    - the occurrence of an event of default by Sierra Pacific in respect of
      subordinated debt securities, or

    - default by Sierra Pacific on any of its obligations under any guarantee
      described in this prospectus,

the holders of the affected trust's preferred securities will have a preference
over the holders of the trust's common securities with respect to payments upon
liquidation of the trust.

    In the case of any event of default by Sierra Pacific in respect of
subordinated debt securities, the holder of the common securities will be deemed
to have waived any right in connection with the event of default until the event
of default with respect to the preferred securities have been cured, waived or
otherwise eliminated. Until all events of default with respect to the preferred
securities have been cured in this manner, waived or otherwise eliminated, the
property trustee of the trust shall act solely on behalf of the holders of the
trust's preferred securities and not on behalf of the holder of the common
securities, and only the holders of the preferred securities will have the right
to direct the property trustee to act on their behalf.

AMENDMENT OF DECLARATIONS

    Each declaration may be modified and amended if approved and executed by the
administrative trustees of a trust, except that:

    - no amendment shall be made, and any purported amendment shall be void and
      ineffective, to the extent the result thereof would be to:

     (1) cause a trust to fail to be classified for the purposes of United
         States Federal income taxation as a grantor trust;

     (2) affect the powers or the rights of the property trustee or the Delaware
         trustee of a trust without their written consent; or

     (3) cause a trust to be deemed an "investment company" which is required to
         be registered under the Investment Company Act;

    - at the time after a trust has issued any securities which remain
      outstanding, any amendment which would materially adversely affect the
      rights, privileges or preferences of any holder of the securities may be
      effected only with the additional requirements as may be set forth in the
      terms of the securities of a trust;

                                       18
<PAGE>
    - provisions in the declarations regarding the transferability of the common
      securities of a trust and regarding the amendment of the declarations
      cannot be amended without the consent of all of the holders of the
      securities of a trust;

    - provisions in the declarations regarding Sierra Pacific cannot be amended
      without Sierra Pacific's consent; and

    - Sierra Pacific's rights to increase or decrease the number of, and appoint
      and remove, trustees of a trust shall not be amended without Sierra
      Pacific's consent.

    Notwithstanding the foregoing, each declaration may be amended from time to
time by the holders of a majority in liquidation amount of the common securities
of the trust and its property trustee, without the consent of the holders of the
preferred securities, to:

    - cure any ambiguity;

    - correct or supplement any provision in a declaration that may be defective
      or inconsistent with any other provision in that declaration or to make
      any other provisions with respect to matters or questions arising under a
      declaration, which shall not be inconsistent with the other provisions of
      the declaration;

    - add to the covenants, restrictions or obligations of Sierra Pacific;

    - ensure the applicable trust's classification as a grantor trust for United
      States Federal income tax purposes and conform to any change in the
      Investment Company Act, the Trust Indenture Act or the rules or
      regulations under either law; and

    - to modify, eliminate or add to any provisions of a declaration to the
      extent necessary to ensure that the applicable trust will not be required
      to register as an "investment company" under the Investment Company Act.

VOTING RIGHTS

    Except as provided below and under "Description of Preferred Securities
Guarantee--Amendments and Assignment" and as otherwise required by law and the
declarations, the holders of the preferred securities of the trusts will have no
voting rights.

    The holders of a majority in aggregate liquidation amount of the preferred
securities of each trust have the right to:

    - direct the time, method and place of conducting any proceeding for any
      remedy available to the property trustee of the trust; or

    - direct the exercise of the power conferred upon the property trustee under
      the trust's declaration, including the right to direct the property
      trustee, as the holder of a series of subordinated debt securities, to

     (a) exercise the remedies available under the subordinated indenture with
         respect to the subordinated debt securities;

     (b) waive any event of default under the subordinated indenture that is
         waivable;

     (c) cancel an acceleration of the principal of the subordinated debt
securities; or

     (d) consent to any amendment, modification or termination of the
subordinated indenture or the subordinated debt securities where consent shall
be required.

However, if the subordinated indenture requires the consent of the holders of
more than a majority in aggregate principal amount of a series of subordinated
debt securities with respect to any waiver or

                                       19
<PAGE>
consent, then the property trustee for the series must get approval of the
holders of the super-majority in liquidation amount of the series of preferred
securities.

    In addition, before taking any of the foregoing actions, the property
trustee must obtain an opinion of counsel stating that, as a result of the
action, the trust will continue to be classified as a grantor trust for United
States Federal income tax purposes.

    The property trustee of a trust will notify all preferred securities holders
of any notice received from the subordinated indenture trustee with respect to
the subordinated debt securities held by the trust.

    Any required approval or direction of holders of preferred securities of a
trust may be given at a separate meeting of holders of the preferred securities
of the trust convened for that purpose, at a meeting of all of the holders of
Trust Securities or through written consent.

    If a vote of preferred securities holders is taken or a consent is obtained,
any preferred securities that are owned by Sierra Pacific or any of its
affiliates will, for purposes of the vote or consent, be treated as if they were
not outstanding. This means:

    - Sierra Pacific and any of its affiliates will not be able to vote on or
      consent to matters requiring the vote or consent of holders of preferred
      securities; and

    - any preferred securities owned by Sierra Pacific or any of its affiliates
      will not be counted in determining whether the required percentage of
      votes or consents has been obtained.

DECLARATION EVENTS OF DEFAULT

    Any one of the following events constitutes an "event of default" under the
declarations with respect to the preferred securities issued thereunder:

    - the occurrence of an event of default under the subordinated indenture
      (see "Description of Debt Securities--Events of Default");

    - a default by the property trustee in the payment of any distribution when
      it becomes due and payable, and continuation of the default for a period
      of 30 days;

    - a default by the property trustee in the payment of the redemption price
      of any Trust Security when it becomes due and payable;

    - default in the performance or breach, in any material respect, of any
      covenant or warranty of the administrative trustees, and continuation of
      the default or breach for a period of 60 days after appropriate written
      notice under the declaration; or

    - the occurrence of events of bankruptcy or insolvency with respect to the
      property trustee and the failure by Sierra Pacific to appoint a successor
      property trustee within 60 days thereof.

    Sierra Pacific and the administrative trustees of each trust must file
annually with the property trustee of each trust a certificate stating whether
or not they are in compliance with all the applicable conditions and covenants
under the applicable declaration.

    Upon the occurrence of an event of default under a declaration, the property
trustee, as the sole holder of the subordinated debt securities held by the
applicable trust, will have the right under the subordinated indenture to
declare the principal of, premium, if any, and interest on the subordinated debt
securities to be immediately due and payable.

    If the property trustee fails to enforce its rights under the terms of the
applicable subordinated debt securities after a holder of preferred securities
has made a written request, the holder may, to the extent permitted by
applicable law, sue Sierra Pacific, or seek other remedies, to enforce the
property

                                       20
<PAGE>
trustee's rights under the subordinated indenture without first instituting a
legal proceeding against the property trustee, the trust or any other person or
entity.

    If Sierra Pacific fails to pay principal, premium, if any, or interest on a
series of subordinated debt securities when payable, then a holder of the
related preferred securities issued by the affected trust may directly sue
Sierra Pacific or seek other remedies, to collect its pro rata share of payments
owed.

MERGER, CONSOLIDATION OR AMALGAMATION OF THE TRUSTS

    Neither trust may consolidate, amalgamate, convert into, merge with or into,
or be replaced by, or convey, transfer or lease its properties and assets
substantially as an entirety to, any corporation or other entity, except as
described below or as described in "Liquidation Distribution Upon Dissolution".
Each trust may, with the consent of a majority of the administrative trustees of
the trust and without the consent of the holders of the Trust Securities, the
property trustee or the Delaware trustee consolidate, amalgamate, convert into,
merge with or into, or be replaced by a new trust organized under the laws of
any State of the United States; provided, that:

    - if the trust is not the surviving entity, the successor entity either:

      - substitutes for the preferred securities other securities having
        substantially the same terms as the preferred securities (the "successor
        securities"), so long as the successor securities rank the same as the
        trust securities with respect to distributions, assets and payments; or

      - expressly assumes all of the obligations of the trust under the Trust
        Securities, and

    - Sierra Pacific expressly acknowledges a trustee of the successor entity
      possessing the same powers and duties as the property trustee;

    - the preferred securities or any successor securities are listed, or any
      successor securities will be listed upon notification of issuance, on any
      national securities exchange or with another organization on which the
      preferred securities are then listed or quoted;

    - any merger, consolidation, amalgamation, conversion or replacement does
      not cause the preferred securities, including any successor securities, to
      be downgraded by any nationally recognized statistical rating
      organization;

    - any merger, consolidation, amalgamation, conversion or replacement does
      not adversely affect the rights, preferences and privileges of the holders
      of the preferred securities, including any successor securities, in any
      material respect;

    - the successor entity has a purpose substantially identical to that of the
      trust;

    - Sierra Pacific guarantees the obligations of the successor entity under
      the successor securities to the same extent as provided by the trust
      guarantee; and

    - before any merger, consolidation, amalgamations, conversion or
      replacement, Sierra Pacific has received an opinion of a nationally
      recognized independent counsel to the trust experienced in these matters
      to the effect that:

      - any merger, consolidation, amalgamations, conversion or replacement will
        not adversely affect the rights, preferences and privileges of the
        holders of the preferred securities, including any successor securities,
        in any material respect, other than with respect to any dilution of the
        holders' interest in the new entity;

      - following any merger, consolidation, amalgamations, conversion or
        replacement, neither the trust nor the successor entity will be required
        to register as an investment company under the Investment Company Act;
        and

                                       21
<PAGE>
      - following any merger, consolidation, amalgamations, conversion or
        replacement, the trust, or any successor trust, will not be classified
        as an association or a publicly traded partnership taxable as a
        corporation for United States Federal income tax purposes.

Notwithstanding the foregoing, each trust shall not, except with the consent of
holders of 100% in liquidation amount of the preferred securities of the trust,
consolidate, amalgamate, merge with or into, or be replaced by any other entity
or permit any other entity to consolidate, amalgamate, conversion, merge with or
into, or replace it, if any consolidation, amalgamation, conversion, merger or
replacement would cause the trust or the successor entity to be classified as an
association or a publicly traded partnership taxable as a corporation for United
States Federal income tax purposes.

REMOVAL AND REPLACEMENT OF TRUSTEES

    Only the holder of a trust's common securities has the right to remove or
replace the trustees of the applicable trust. The resignation or removal of any
trustee and the appointment of a successor trustee shall be effective only on
the acceptance of appointment by the successor trustee under the provisions of
the applicable declaration.

REGISTRAR, TRANSFER AGENT, AND PAYING AGENT

    Unless otherwise specified in the applicable prospectus supplement, the
property trustee of a trust will act as registrar, transfer agent and paying
agent for the preferred securities of the trust.

    Registration of transfers of the preferred securities of a trust will be
effected without charge by or on behalf of the trust, but upon payment and with
the giving of any indemnity as the trust or Sierra Pacific may require, in
respect of any tax or other government charges which may be imposed in relation
to it.

    The trusts will not be required to register or cause to be registered the
transfer of their preferred securities after the preferred securities have been
called for redemption.

BOOK-ENTRY ONLY ISSUANCE--THE DEPOSITORY TRUST COMPANY

    DESCRIPTION OF THE GLOBAL CERTIFICATES

    DTC will act as securities depository for the preferred securities and, to
the extent distributed to the holders of the preferred securities, the
subordinated debt securities held by a trust. The preferred securities will be
issued only as fully-registered securities registered in the name of Cede & Co.
(DTC's nominee). One or more fully-registered global certificates, representing
the total aggregate number of preferred securities, will be issued and will be
deposited with DTC.

    DTC PROCEDURES

    DTC is a limited-purpose trust company organized under the New York Banking
Law, a "banking organization" within the meaning of the New York Banking Law, a
member of the Federal Reserve System, a "clearing corporation" within the
meaning of the New York Uniform Commercial Code, and a "clearing agency"
registered pursuant to the provisions of Section 17A of the Securities Exchange
Act of 1934, as amended. DTC holds securities that its participants deposit with
DTC. DTC also facilitates the settlement among participants of securities
transactions, such as transfers and pledges, in deposited securities through
electronic computerized book-entry changes in participants' accounts, thereby
eliminating the need for physical movement of securities certificates.
Participants in DTC include securities brokers and dealers, banks, trust
companies, clearing corporations and other organizations. DTC is owned by a
number of its participants and by the New York Stock Exchange, the American
Stock Exchange and the National Association of Securities Dealers, Inc. Access
to the DTC system is also available to others, including securities brokers and
dealers, banks and trust companies that clear

                                       22
<PAGE>
through or maintain a custodial relationship with a participant, either directly
or indirectly. The rules applicable to DTC and its participants are on file with
the SEC.

    Purchases of preferred securities within the DTC system must be made by or
through participants, which will receive a credit for the preferred securities
on DTC's records. The ownership interest of each beneficial owner of preferred
securities is in turn to be recorded on the participants' and indirect
participants' records. Beneficial owners will not receive written confirmation
from DTC of their purchases, but beneficial owners are expected to receive
written confirmations providing details of the transactions, as well as periodic
statements of their holdings, from the participants or indirect participants
through which the beneficial owners purchased preferred securities. Transfers of
ownership interests in preferred securities are to be accomplished by entries
made on the books of participants and indirect participants acting on behalf of
beneficial owners. Beneficial owners will not receive certificates representing
their ownership interests in the preferred securities, except in the event that
use of the book-entry system for the preferred securities is discontinued.

    DTC has no knowledge of the actual beneficial owners of preferred
securities; DTC's records reflect only the identity of the participants to whose
accounts the preferred securities are credited, which may or may not be the
beneficial owners. The participants and indirect participants will remain
responsible for keeping account of their holdings on behalf of their customers.

    So long as DTC, or its nominee, is the registered owner or holder of a
global certificate, DTC or the nominee, as the case may be, will be considered
the sole owner or holder of the preferred securities being represented for all
purposes under the declarations. No beneficial owner of an interest in a global
certificate will be able to transfer that interest except in accordance with
DTC's applicable procedures, in addition to those provided for under the
declarations.

    DTC has advised Sierra Pacific that it will take any action permitted to be
taken by a holder of preferred securities, including the presentation of
preferred securities for exchange as described below, only at the direction of
one or more participants to whose account the DTC interests in the global
certificates are credited and only in respect of the portion of the aggregate
liquidation amount of the preferred securities as to which the participant or
participants has or have given the direction. Also, if there is an event of
default under the declarations, DTC will exchange the global certificates for
certificated securities, which it will distribute to its participants in
accordance with its customary procedures.

    Delivery of notices and other communications by DTC to participants, by
participants to indirect participants, and by participants and indirect
participants to beneficial owners will be governed by arrangements among them,
subject to any statutory or regulatory requirements as may be in effect from
time to time.

    Redemption notices in respect of preferred securities held in book-entry
form will be sent to Cede & Co. If less than all of the preferred securities are
being redeemed, DTC will determine the amount of the interest of each
participant to be redeemed in accordance with its procedures.

    Although voting with respect to preferred securities is limited, in those
cases where a vote is required, neither DTC nor Cede & Co. will itself consent
or vote with respect to the preferred securities. Under its usual procedures,
DTC would mail an omnibus proxy to the issuing trust as soon as possible after
the record date. The omnibus proxy assigns Cede & Co.'s consenting or voting
rights to those participants to whose accounts the preferred securities are
allocated on the record date identified in a listing attached to the omnibus
proxy.

    Distributions on the preferred securities held in book-entry form will be
made to DTC in immediately available funds. DTC's practice is to credit
participants' accounts on the relevant payment date in accordance with their
respective holdings shown on DTC's records unless DTC has reason to believe that
it will not receive payments on the payment date. Payments by participants and
indirect

                                       23
<PAGE>
participants to beneficial owners will be governed by standing instructions and
customary practices and will be the responsibility of the participants and
indirect participants and not of DTC, the trusts or Sierra Pacific, subject to
any statutory or regulatory requirements as may be in effect from time to time.
Payment of any distributions to DTC is the responsibility of the trusts,
disbursement of those payments to participants is the responsibility of DTC, and
disbursement of those payments to the beneficial owners is the responsibility of
participants and indirect participants.

    Except as described in the applicable prospectus supplement, a beneficial
owner of an interest in a global certificate will not be entitled to receive
physical delivery of the preferred securities. Accordingly, each beneficial
owner must rely on the procedures of DTC to exercise any rights under the
preferred securities.

    Although DTC has agreed to the foregoing procedures in order to facilitate
transfers of interests in the global certificates among participants of DTC, DTC
is under no obligation to perform or continue to perform the procedures, and the
procedures may be discontinued at any time. Neither Sierra Pacific nor the
trusts, nor any underwriter, dealer or agent participating in the offering will
have any responsibility or liability for the performance by DTC or its
participants or indirect participants under the rules and procedures governing
DTC. DTC may discontinue providing its services as securities depository with
respect to the preferred securities at any time by giving notice to the issuing
trusts. If a successor securities depository is not obtained, preferred
securities certificates are required to be printed and delivered to the property
trustee. Additionally, each trust, with the consent of Sierra Pacific, may
decide to discontinue use of the system of book-entry transfers through DTC or
any successor depository. In that event, certificates for preferred securities
will be printed and delivered to the property trustee. In each of the above
circumstances, Sierra Pacific will appoint a paying agent with respect to the
preferred securities.

    The laws of some jurisdictions require that certain purchasers of securities
take physical delivery of securities in definitive form. These laws may impair
the ability to transfer beneficial interests in the global preferred securities
as represented by a global certificate.

    The information in this section concerning DTC and DTC's system has been
obtained from sources that Sierra Pacific believes to be reliable, but Sierra
Pacific takes no responsibility for the accuracy of the information.

INFORMATION CONCERNING THE PROPERTY TRUSTEE

    The property trustee of each trust, before the occurrence of a default with
respect to a trust's securities, undertakes to perform only the duties as are
specifically set forth in the trust' declaration and, after default, shall
exercise the same degree of care as a prudent individual would exercise in the
conduct of his or her own affairs. Otherwise, the property trustee is under no
obligation to exercise any of the powers vested in it by a trust's declaration
at the request of any holder of the trust's preferred securities, unless offered
reasonable indemnity satisfactory to the property trustee by the holder against
the costs, expenses and liabilities which might be incurred in connection with
the exercise of any powers.

GOVERNING LAW

    The declarations and the preferred securities issued by the trusts will be
governed by, and construed in accordance with, the internal laws of the State of
Delaware.

                                       24
<PAGE>
MISCELLANEOUS

    The administrative trustees of a trust are authorized and directed to
conduct the affairs of and to operate the trust in a way that the trust will not
be deemed to be an investment company required to be registered under the
Investment Company Act or characterized as other than a grantor trust for United
States Federal income tax purposes. In this connection, the administrative
trustees of a trust are authorized to take any action, not inconsistent with
applicable law, the trust's certificate of trust or its declaration that the
administrative trustees determine in their discretion to be necessary or
desirable for those purposes as long as the action does not adversely affect the
interests of the holders of the preferred securities.

    Holders of the preferred securities of the trust will have no preemptive or
similar rights.

               DESCRIPTION OF THE PREFERRED SECURITIES GUARANTEES

    Set forth below is a summary of information concerning the preferred
securities guarantees which will be executed and delivered by Sierra Pacific for
the benefit of the holders of the preferred securities of a trust. The summary
is not complete and is subject in all respects to the provisions of, and is
qualified in its entirety by reference to, the preferred securities guarantees,
which are filed as an exhibit to the registration statement of which this
prospectus is a part. Each preferred securities guarantee incorporates by
reference the terms of, and will be qualified as an indenture under, the Trust
Indenture Act. The Bank of New York will act as the trustee under each preferred
securities guarantee ("guarantee trustee") and will hold the preferred
securities guarantees for the respective benefit of the holders of the preferred
securities.

GENERAL

    Under each preferred securities guarantee, Sierra Pacific will irrevocably
agree, on a subordinated basis and to the extent set forth in each preferred
securities guarantee, to pay in full to the holders of the preferred securities
of the trust, except to the extent paid by the trusts, as and when due,
regardless of any defense, right of set off or counterclaim which a trust may
have or assert, the following payments (the "guarantee payments"), without
duplication:

    - any accumulated and unpaid distributions on the preferred securities of a
      trust to the extent the trust has funds available for distribution;

    - the redemption price with respect to any preferred securities called for
      redemption by the trust, to the extent the trust has funds available for
      payment; and

    - upon a voluntary or involuntary dissolution, winding-up or termination of
      the trust, other than in connection with the distribution of subordinated
      debt securities to the holders of the preferred securities or the
      redemption of all of the preferred securities, the lesser of:

      - the aggregate of the liquidation amount and all accumulated and unpaid
        distributions on the preferred securities, and

      - the amount of assets of the trust remaining available for distribution
        to holders of the preferred securities upon the liquidation of the
        trust.

Sierra Pacific's obligation to make a guarantee payment may be satisfied by
direct payment of the required amounts by Sierra Pacific to the holders of the
preferred securities or by causing the trust to pay these amounts to holders.

    Each preferred securities guarantee will be a guarantee on a subordinated
basis with respect to the preferred securities of a trust but will only apply to
any payment of distributions or the redemption price, or to payments upon the
dissolution, winding-up or termination of a trust, to the extent the trust

                                       25
<PAGE>
shall have funds available. If Sierra Pacific fails to make payments on the
subordinated debt securities held by a trust, the trust would lack available
funds for the payment of distributions or amounts payable on redemption of its
preferred securities, and in that event holders of the preferred securities
would not be able to rely upon the preferred securities guarantee for payment of
these amounts. Instead, holders of the preferred securities will have the
remedies described under "Description of the Preferred Securities--Declaration
Events of Default", including the right to direct the guarantee trustee to
enforce the restriction of payments by Sierra Pacific and its subsidiaries on
its capital stock. See "--Events of Default" below.

    The preferred securities guarantees, when taken together with Sierra
Pacific's obligations under the declarations of trust, the subordinated
indenture, subordinated debt securities, and the expense agreement (see below),
constitute a guarantee to the extent set forth in this prospectus by Sierra
Pacific of the distribution, redemption and liquidation payments payable to the
holders of the preferred securities of the trusts. No single document executed
by Sierra Pacific in connection with the issuance of any series of preferred
securities will provide for its full, irrevocable and unconditional guarantee of
the preferred securities.

EVENTS OF DEFAULT

    It shall be an event of default under a preferred securities guarantees if
Sierra Pacific fails to perform any of its payment or other obligations set
forth in the preferred securities guarantee.

    The holders of a majority in liquidation amount of the preferred securities
of a trust have the right to direct the time, method and place of conducting any
proceeding for any remedy available to the guarantee trustee or to direct the
exercise of any power conferred upon the guarantee trustee under the preferred
securities guarantee applicable to the trust. If the guarantee trustee fails to
enforce its rights under a preferred securities guarantee after a holder of the
preferred securities has made a written request, the holder may institute a
legal proceeding directly against Sierra Pacific to enforce the guarantee
trustee's rights under that preferred securities guarantee, without first
instituting a legal proceeding against the applicable trust, the guarantee
trustee or any other person or entity. If Sierra Pacific has failed to make a
guarantee payment under a preferred securities guarantee, a holder of the
preferred securities may directly institute a proceeding in the holder's own
name against Sierra Pacific for enforcement of the preferred securities
guarantee for payment.

STATUS OF THE PREFERRED SECURITIES GUARANTEES; SUBORDINATION

    The preferred securities guarantees will constitute an unsecured obligation
of Sierra Pacific and will rank subordinate and junior in right of payment to
all senior indebtedness of Sierra Pacific. Sierra Pacific is a non-operating
holding company and substantially all of its operating assets are owned by its
subsidiaries. Sierra Pacific relies primarily on dividends from its subsidiaries
to meet its obligations for payment of principal and interest on its outstanding
debt and corporate expenses. Accordingly, the guarantees will be effectively
subordinated to all existing and future liabilities of Sierra Pacific's
subsidiaries. Except as otherwise provided in the applicable prospectus
supplement, there is no limit on the incurrence or issuance of other secured or
unsecured debt by Sierra Pacific or its subsidiaries. Holders of guarantees
should look only to the assets of Sierra Pacific for payments of principal,
interest and premium, if any.

    The preferred securities guarantees will rank PARI PASSU with all other
guarantees issued by Sierra Pacific.

AMENDMENTS AND ASSIGNMENT

    Except with respect to any changes that do not materially adversely affect
the rights of holders of preferred securities, in which case no vote will be
required, a preferred securities guarantee may be

                                       26
<PAGE>
amended only with the prior approval of the holders of at least a majority in
liquidation amount of all the outstanding preferred securities of the affected
trust. The manner of obtaining any approval of holders of the preferred
securities will be as set forth under "Description of the Preferred Securities
of the Trusts--Voting Rights." All guarantees and agreements contained in a
preferred securities guarantee shall bind the successors, assigns, receivers,
trustees and representatives of Sierra Pacific and shall inure to the benefit of
the holders of the preferred securities of the applicable trust then
outstanding. Except in connection with the permitted merger or consolidation of
Sierra Pacific with or into another entity or permitted sale, transfer or lease
of Sierra Pacific's assets to another entity in which the surviving corporation,
if other than Sierra Pacific, assumes Sierra Pacific's obligations under the
preferred securities guarantees, Sierra Pacific may not assign its rights or
delegate its obligations under the preferred securities guarantees without the
prior approval of the holders of at least a majority of the aggregate stated
liquidation amount of the preferred securities then outstanding.

TERMINATION OF THE PREFERRED SECURITIES GUARANTEES

    A preferred securities guarantee will terminate as to each holder of the
preferred securities of the applicable trust upon:

    - full payment of the redemption price of all the preferred securities,

    - distribution of the subordinated debt securities held by the trust to the
      holders of the preferred securities, or

    - full payment of the amounts payable under the declaration upon liquidation
      of the trust.

INFORMATION CONCERNING THE GUARANTEE TRUSTEE

    The guarantee trustee of each trust, before the occurrence of a default with
respect to a preferred securities guarantee, undertakes to perform only those
duties as are specifically set forth in a preferred securities guarantee and,
after default with respect to the preferred securities guarantee, shall exercise
the same degree of care as a prudent man would exercise in the conduct of his
own affairs. The guarantee trustee is under no obligation to exercise any of the
powers vested in it by a preferred securities guarantee at the request of any
holder of preferred securities unless it is offered reasonable indemnity against
the costs, expenses and liabilities that might be incurred in connection with
the exercise of those powers.

GOVERNING LAW

    The preferred securities guarantees will be governed by, and construed
under, the internal laws of the State of New York.

THE EXPENSE AGREEMENT

    Under an expense agreement entered into by Sierra Pacific under each trust
agreement, Sierra Pacific will irrevocably and unconditionally guarantee to each
person or entity to whom a trust becomes indebted or liable, the full payment of
any costs, expenses or liabilities of the trust, other than obligations of the
trust to pay to the holders of the trust's preferred securities the amounts due
pursuant to the terms of the preferred securities.

                                       27
<PAGE>
    RELATIONSHIP AMONG PREFERRED SECURITIES, PREFERRED SECURITIES GUARANTEES
              AND SUBORDINATED DEBT SECURITIES HELD BY THE TRUSTS

    Payments of distributions and redemption and liquidation payments due on
each series of preferred securities (to the extent the applicable trust has
funds available for the payments) will be guaranteed by Sierra Pacific to the
extent described under "Description of Preferred Securities Guarantees." No
single document executed by Sierra Pacific in connection with the issuance of
any series of preferred securities will provide for its full, irrevocable and
unconditional guarantee of the preferred securities. It is only the combined
operation of Sierra Pacific's obligations under a preferred securities
guarantees, the declaration, subordinated indenture and subordinated debt
securities that has the effect of providing a full, irrevocable and
unconditional guarantee of a trust's obligations with respect to its preferred
securities.

    As long as Sierra Pacific makes payments of interest and other payments when
due on the subordinated debt securities held by a trust, the payments will be
sufficient to cover the payment of distributions and redemption and liquidation
payments due on the preferred securities issued by the trust, primarily because:

    - the aggregate principal amount of the subordinated debt securities will be
      equal to the sum of the aggregate liquidation amount of the preferred and
      common securities of the trust;

    - the interest rate and interest and other payment dates on the subordinated
      debt securities will match the distribution rate and any distribution and
      other payment dates for the preferred securities;

    - Sierra Pacific will pay for any and all costs, expenses and liabilities of
      the trust except for the trust's obligations under its preferred
      securities (and Sierra Pacific has agreed to guarantee the payments); and

    - the declaration provides that the trust will not engage in any activity
      that is not consistent with the limited purposes of the trust.

    If and to the extent that Sierra Pacific does not make payments on
subordinated debt securities held by a trust, the trust will not have funds
available to make payments of distributions or other amounts due on its
preferred securities. In those circumstances, holders of the preferred
securities will not be able to rely upon the preferred securities guarantee for
payment of these amounts. Instead, holders of the preferred securities may
directly sue Sierra Pacific or seek other remedies to collect their pro rata
share of payments owed. If a holder of preferred securities sues Sierra Pacific
to collect payment, then Sierra Pacific will assume the holders rights as a
holder of preferred securities under the applicable trust's declaration to the
extent Sierra Pacific makes a payment to the holder of preferred securities in
any legal action.

    A holder of any preferred security may sue Sierra Pacific, or seek other
remedies, to enforce its rights under a preferred securities guarantee without
first suing the guarantee trustee, the applicable trust or any other person or
entity.

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                              PLAN OF DISTRIBUTION

    Sierra Pacific may sell the senior debt securities or subordinated debt
securities and the trusts may sell their preferred securities being offered
hereby in one or more of the following ways from time to time:

    - to underwriters for resale to the public or to institutional investors;

    - directly to institutional investors;

    - directly to agents;

    - through agents to the public or to institutional investors; or

    - if indicated in the prospectus supplement, pursuant to delayed delivery
      contracts, by remarketing firms or by other means.

    The prospectus supplements will set forth the terms of the offering of each
series of securities, including the name or names of any underwriters or agents,
the purchase price of the securities and the proceeds to Sierra Pacific or the
trusts, as the case may be, from the sale, any underwriting discounts or agency
fees and other items constituting underwriters' or agents' compensation, any
discounts or concessions allowed or reallowed or paid to dealers and any
securities exchanges on which the securities may be listed.

    If underwriters are utilized in the sale, the securities will be acquired by
the underwriters for their own account and may be resold from time to time in
one or more transactions, including negotiated transactions, at a fixed public
offering price or prices, which may be changed, or at market or varying prices
determined at the time of sale.

    Unless otherwise set forth in a prospectus supplement, the obligations of
the underwriters to purchase any series of securities will be subject to
conditions precedent and the underwriters will be obligated to purchase all of
the series of securities, if any are purchased.

    If a dealer is utilized in the sale of securities, Sierra Pacific or the
trusts will sell the securities to the dealer, as principal. The dealer may then
resell the securities to the public at varying prices to be determined by the
dealer at the time of resale.

    Securities may also be offered and sold, if so indicated in the prospectus
supplement, in connection with a remarketing agreement upon their purchase, in
accordance with a redemption or repayment pursuant to their terms, or otherwise,
by one or more firms ("remarketing firms") acting as principals for their own
accounts or as agents for Sierra Pacific. Any remarketing firm will be
identified and the terms of its agreement, if any, with Sierra Pacific and its
compensation will be described in the prospectus supplement.

    Underwriters, agents, dealers and remarketing firms may be entitled under
agreements entered into with Sierra Pacific and/or the trusts to indemnification
by Sierra Pacific and/or the trusts against civil liabilities, including
liabilities under the Securities Act of 1933, or to contribution with respect to
payments which the underwriters or agents may be required to make in respect
thereof. Underwriters, agents, dealers and remarketing firms may be customers
of, engage in transactions with, or perform services for Sierra Pacific and its
subsidiaries and affiliates in the ordinary course of business.

    Each series of securities will be a new issue of securities and will have no
established trading market. Any underwriters to whom securities are sold by
Sierra Pacific or by the trusts for public offering and sale may make a market
in the securities, but the underwriters will not be obligated to do so and may
discontinue any market making at any time without notice. The securities may or
may not be listed on a national securities exchange or a foreign securities
exchange.

                                       29
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                      WHERE YOU CAN FIND MORE INFORMATION

    We file reports, proxy statements and other information with the SEC. Our
SEC filings are also available over the Internet at the SEC's web site at
http://www.sec.gov. You may also read and copy any document we file by visiting
the SEC's public reference rooms in Washington, D.C., New York, New York, and
Chicago, Illinois. Please call the SEC at 1-800-SEC-0330 for further information
about the public reference rooms. You may also inspect our SEC reports and other
information at the New York Stock Exchange, Inc., 20 Broad Street, New York, New
York 10005.

    We have filed a registration statement on Form S-3 with the SEC covering the
securities. For further information on Sierra Pacific, the trust and the
securities, you should refer to our registration statement and its exhibits.
This prospectus summarizes material provisions of contracts and other documents
that we refer you to. Because the prospectus may not contain all the information
that you may find important, you should review the full text of these documents.
We have included copies of these documents as exhibits to our registration
statement.

               INCORPORATION OF INFORMATION WE FILE WITH THE SEC

    The SEC allows us to incorporate by reference the information we file with
them, which means:

    - incorporated documents are considered part of the prospectus;

    - we can disclose important information to you by referring you to those
      documents; and

    - information that we file with the SEC will automatically update and
      supersede this incorporated information.

    We incorporate by reference the documents listed below which were filed with
the SEC under the Exchange Act:

    - our annual report on Form 10-K for the year ended December 31, 1999, which
      is combined with the annual report on Form 10-K for Nevada Power;

    - Sierra Pacific Power Company's annual report on Form 10-K for the year
      ended December 31, 1999;

    - our current report on Form 8-K dated August 9, 1999 and the 8-K/A
      amendment thereto dated September 20, 1999;

    - our current report on Form 8-K dated April 14, 2000; and

    - our current report on Form 8-K dated April 21, 2000.

    We also incorporate by reference each of the following documents that we
will file with the SEC after the date of this prospectus until this offering is
completed or after the date of this initial registration statement and before
effectiveness of the registration statement:

    - reports filed under Sections 13(a) and (c) of the Exchange Act;

    - definitive proxy or information statements filed under Section 14 of the
      Exchange Act in connection with any subsequent stockholders' meeting; and

    - any reports filed under Section 15(d) of the Exchange Act.

    You should rely only on information contained or incorporated by reference
in this prospectus. We have not authorized any other person to provide you with
different information. If anyone provides you with different or inconsistent
information, you should not rely on it. We are not making an offer to sell these
securities in any jurisdiction where the offer or sale is not permitted.

                                       30
<PAGE>
    You should assume that the information appearing in this prospectus is
accurate as of the date of this prospectus only. Our business, financial
condition and results of operations may have changed since that date.

    You may request a copy of any filings referred to above (excluding
exhibits), at no cost, by contacting us at the following address: Assistant
Treasurer, Sierra Pacific Resources, P.O. Box 30150 (6100 Neil Road), Reno
Nevada 89520-3150, Telephone: (775) 834-4358.

                                 LEGAL OPINIONS

    Unless otherwise indicated in the applicable prospectus supplement, certain
legal matters will be passed upon for Sierra Pacific and the trusts by Choate,
Hall & Stewart (a partnership including professional corporations), Boston,
Massachusetts, counsel to Sierra Pacific, and for the trusts and Sierra Pacific
by Richards, Layton & Finger, P.A., Wilmington, Delaware, special Delaware
counsel to the trusts and Sierra Pacific. Matters of local law will be passed
upon as to the State of Nevada by Woodburn and Wedge, Reno, Nevada. Legal
matters in connection with the offered securities will be passed upon for the
underwriter(s), dealer(s) or agent(s) by Thelen Reid & Priest LLP. Choate, Hall
& Stewart and Thelen Reid & Priest LLP will rely on the opinion of Woodburn and
Wedge, Reno, Nevada, as to matters of Nevada law. Thelen Reid & Priest LLP
represents Sierra Pacific Resources and its utility subsidiaries in connection
with certain federal tax matters.

                                    EXPERTS

    The consolidated financial statements of Sierra Pacific Resources, the
financial statements of Nevada Power Company, the consolidated financial
statements of Sierra Pacific Power Company and the related financial statement
schedules incorporated in this prospectus supplement and accompanying prospectus
by reference from Sierra Pacific Resources', Nevada Power Company's and Sierra
Pacific Power Company's Annual Reports on Form 10-K for the year ended
December 31, 1999 have been audited by Deloitte & Touche LLP, independent
auditors, as stated in their reports, which are incorporated herein by
reference, and have been so incorporated in reliance upon the reports of such
firm given upon their authority as experts in accounting and auditing.

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                                  $300,000,000

                                     [LOGO]

                             8 3/4% NOTES DUE 2005

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                             PROSPECTUS SUPPLEMENT
                          ----------------------------

                              MERRILL LYNCH & CO.
                           CREDIT SUISSE FIRST BOSTON
                              SALOMON SMITH BARNEY

                                  MAY 5, 2000

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