<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 three months ended June 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>                   JUN-30-1998
<PERIOD-TYPE>                        6-MOS
<BOOK-VALUE>                      PER-BOOK
<TOTAL-NET-UTILITY-PLANT>        1,087,498
<OTHER-PROPERTY-AND-INVEST>         14,191
<TOTAL-CURRENT-ASSETS>             152,765
<TOTAL-DEFERRED-CHARGES>           261,727
<OTHER-ASSETS>                           0
<TOTAL-ASSETS>                   1,516,181
<COMMON>                            43,068
<CAPITAL-SURPLUS-PAID-IN>          112,043
<RETAINED-EARNINGS>                284,480
<TOTAL-COMMON-STOCKHOLDERS-EQ>     439,591
<PREFERRED-MANDATORY>               11,950
<PREFERRED>                              0
<LONG-TERM-DEBT-NET>               343,164
<SHORT-TERM-NOTES>                 226,625
<LONG-TERM-NOTES-PAYABLE>                0
<COMMERCIAL-PAPER-OBLIGATIONS>           0
<LONG-TERM-DEBT-CURRENT-PORT>       36,653
<PREFERRED-STOCK-CURRENT>              820
<CAPITAL-LEASE-OBLIGATIONS>         11,322
<LEASES-CURRENT>                     1,255
<OTHER-ITEMS-CAPITAL-AND-LIAB>     444,801
<TOT-CAPITALIZATION-AND-LIAB>    1,516,181
<GROSS-OPERATING-REVENUE>          295,197
<INCOME-TAX-EXPENSE>                17,018
<OTHER-OPERATING-EXPENSES>         417,277
<TOTAL-OPERATING-EXPENSES>         434,295
<OPERATING-INCOME-LOSS>             46,600
<OTHER-INCOME-NET>                   1,499
<INCOME-BEFORE-INTEREST-EXPEN>      48,099
<TOTAL-INTEREST-EXPENSE>            21,475
<NET-INCOME>                        26,624
<PREFERRED-STOCK-DIVIDENDS>            474
<EARNINGS-AVAILABLE-FOR-COMM>       26,150
<COMMON-STOCK-DIVIDENDS>            17,939
<TOTAL-INTEREST-ON-BONDS>           17,220
<CASH-FLOW-OPERATIONS>              67,037
<EPS-PRIMARY>                         1.21
<EPS-DILUTED>                         1.21