<TABLE> <S> <C>
<PAGE>
<ARTICLE> UT
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM FORM 10-Q
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0001035675
<NAME> NSTAR
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-END> JUN-30-2000
<BOOK-VALUE> PER-BOOK
<TOTAL-NET-UTILITY-PLANT> 2,673,169
<OTHER-PROPERTY-AND-INVEST> 375,052
<TOTAL-CURRENT-ASSETS> 976,402
<TOTAL-DEFERRED-CHARGES> 925,781
<OTHER-ASSETS> 479,864
<TOTAL-ASSETS> 5,430,268
<COMMON> 54,544
<CAPITAL-SURPLUS-PAID-IN> 937,082
<RETAINED-EARNINGS> 395,086
<TOTAL-COMMON-STOCKHOLDERS-EQ> 1,386,712
49,399
43,000
<LONG-TERM-DEBT-NET> 1,864,875
<SHORT-TERM-NOTES> 416,000
<LONG-TERM-NOTES-PAYABLE> 0
<COMMERCIAL-PAPER-OBLIGATIONS> 0
<LONG-TERM-DEBT-CURRENT-PORT> 139,231
0
<CAPITAL-LEASE-OBLIGATIONS> 0
<LEASES-CURRENT> 0
<OTHER-ITEMS-CAPITAL-AND-LIAB> 1,531,051
<TOT-CAPITALIZATION-AND-LIAB> 5,430,268
<GROSS-OPERATING-REVENUE> 1,295,456
<INCOME-TAX-EXPENSE> 49,087
<OTHER-OPERATING-EXPENSES> 1,090,013
<TOTAL-OPERATING-EXPENSES> 1,139,100
<OPERATING-INCOME-LOSS> 156,356
<OTHER-INCOME-NET> 7,870
<INCOME-BEFORE-INTEREST-EXPEN> 164,226
<TOTAL-INTEREST-EXPENSE> 94,199
<NET-INCOME> 70,027
2,980
<EARNINGS-AVAILABLE-FOR-COMM> 67,047
<COMMON-STOCK-DIVIDENDS> 55,487
<TOTAL-INTEREST-ON-BONDS> 78,984
<CASH-FLOW-OPERATIONS> 94,680
<EPS-BASIC> 1.19
<EPS-DILUTED> 1.18
</TABLE>
