<ARTICLE> UT
<LEGEND>
This schedule contains summary financial information extracted from the
balance sheet, statement of income and statement of cash flows contained in
Form 10-Q of Commonwealth Energy System for the nine months ended September
30, 1998 and is qualified in its entirety by reference to such financial
statements.
</LEGEND>
<CIK> 0000071304
<NAME> COMMONWEALTH ENERGY SYSTEM
<MULTIPLIER> 1,000
       
                            
<FISCAL-YEAR-END>              DEC-31-1998
<PERIOD-END>                   SEP-30-1998
<PERIOD-TYPE>                        9-MOS
<BOOK-VALUE>                      PER-BOOK
<TOTAL-NET-UTILITY-PLANT>        1,089,617
<OTHER-PROPERTY-AND-INVEST>         13,135
<TOTAL-CURRENT-ASSETS>             172,793
<TOTAL-DEFERRED-CHARGES>           262,921
<OTHER-ASSETS>                           0
<TOTAL-ASSETS>                   1,538,466
<COMMON>                            43,068
<CAPITAL-SURPLUS-PAID-IN>          112,075
<RETAINED-EARNINGS>                291,585
<TOTAL-COMMON-STOCKHOLDERS-EQ>     446,728
<PREFERRED-MANDATORY>               11,380
<PREFERRED>                              0
<LONG-TERM-DEBT-NET>               475,317
<SHORT-TERM-NOTES>                  74,050
<LONG-TERM-NOTES-PAYABLE>                0
<COMMERCIAL-PAPER-OBLIGATIONS>           0
<LONG-TERM-DEBT-CURRENT-PORT>       56,653
<PREFERRED-STOCK-CURRENT>              820
<CAPITAL-LEASE-OBLIGATIONS>         11,251
<LEASES-CURRENT>                     1,375
<OTHER-ITEMS-CAPITAL-AND-LIAB>     460,892
<TOT-CAPITALIZATION-AND-LIAB>    1,538,466
<GROSS-OPERATING-REVENUE>          714,501
<INCOME-TAX-EXPENSE>                20,449
<OTHER-OPERATING-EXPENSES>         631,493
<TOTAL-OPERATING-EXPENSES>         651,942
<OPERATING-INCOME-LOSS>             62,559
<OTHER-INCOME-NET>                  14,393
<INCOME-BEFORE-INTEREST-EXPEN>      76,952
<TOTAL-INTEREST-EXPENSE>            34,258
<NET-INCOME>                        42,694
<PREFERRED-STOCK-DIVIDENDS>            708
<EARNINGS-AVAILABLE-FOR-COMM>       41,986
<COMMON-STOCK-DIVIDENDS>            26,196
<TOTAL-INTEREST-ON-BONDS>           26,708
<CASH-FLOW-OPERATIONS>              69,257
<EPS-PRIMARY>                         1.95
<EPS-DILUTED>                         1.95