<ARTICLE> UT
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM
THE CONSOLIDATED BALANCE SHEET, CONSOLIDATED STATEMENT OF INCOME, AND
CONSOLIDATED STATEMENT OF CASH FLOWS OF NIAGARA MOHAWK HOLDINGS, INC.
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL
STATEMENTS.
</LEGEND>
<CIK> 0001079182
<NAME> NIAGARA MOHAWK HOLDINGS, INC.
<MULTIPLIER> 1000

                             
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1999
<PERIOD-END>                               DEC-31-1999
<BOOK-VALUE>                                  PER-BOOK
<TOTAL-NET-UTILITY-PLANT>                      5888242
<OTHER-PROPERTY-AND-INVEST>                     484735
<TOTAL-CURRENT-ASSETS>                          674239
<TOTAL-DEFERRED-CHARGES>                       5517786
<OTHER-ASSETS>                                  105433
<TOTAL-ASSETS>                                12670435
<COMMON>                                          1874
<CAPITAL-SURPLUS-PAID-IN>                      2520430
<RETAINED-EARNINGS>                             610952
<TOTAL-COMMON-STOCKHOLDERS-EQ>                 2976089
<PREFERRED-MANDATORY>                            61370
<PREFERRED>                                     440000
<LONG-TERM-DEBT-NET>                           5042588
<SHORT-TERM-NOTES>                                   0
<LONG-TERM-NOTES-PAYABLE>                            0
<COMMERCIAL-PAPER-OBLIGATIONS>                       0
<LONG-TERM-DEBT-CURRENT-PORT>                   613740
<PREFERRED-STOCK-CURRENT>                         7620
<CAPITAL-LEASE-OBLIGATIONS>                          0
<LEASES-CURRENT>                                     0
<OTHER-ITEMS-CAPITAL-AND-LIAB>                 3529028
<TOT-CAPITALIZATION-AND-LIAB>                 12670435
<GROSS-OPERATING-REVENUE>                      4084186
<INCOME-TAX-EXPENSE>                             19180
<OTHER-OPERATING-EXPENSES>                     3558034
<TOTAL-OPERATING-EXPENSES>                     3558034
<OPERATING-INCOME-LOSS>                         526152
<OTHER-INCOME-NET>                                3795
<INCOME-BEFORE-INTEREST-EXPEN>                  529947
<TOTAL-INTEREST-EXPENSE>                        485240
<NET-INCOME>                                   (35088)
<PREFERRED-STOCK-DIVIDENDS>                      36808
<EARNINGS-AVAILABLE-FOR-COMM>                  (35088)
<COMMON-STOCK-DIVIDENDS>                             0
<TOTAL-INTEREST-ON-BONDS>                            0
<CASH-FLOW-OPERATIONS>                          758431
<EPS-BASIC>                                    (.19)
<EPS-DILUTED>                                        0