<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, 1997 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-31-1997
<PERIOD-END>                   SEP-30-1997
<PERIOD-TYPE>                        9-MOS
<BOOK-VALUE>                      PER-BOOK
<TOTAL-NET-UTILITY-PLANT>        1,045,847
<OTHER-PROPERTY-AND-INVEST>         14,446
<TOTAL-CURRENT-ASSETS>             165,757
<TOTAL-DEFERRED-CHARGES>           210,891
<OTHER-ASSETS>                           0
<TOTAL-ASSETS>                   1,436,961
<COMMON>                            43,064
<CAPITAL-SURPLUS-PAID-IN>          111,838
<RETAINED-EARNINGS>                266,861
<TOTAL-COMMON-STOCKHOLDERS-EQ>     421,763
<PREFERRED-MANDATORY>               12,200
<PREFERRED>                              0
<LONG-TERM-DEBT-NET>               379,458
<SHORT-TERM-NOTES>                  61,050
<LONG-TERM-NOTES-PAYABLE>                0
<COMMERCIAL-PAPER-OBLIGATIONS>           0
<LONG-TERM-DEBT-CURRENT-PORT>       17,653
<PREFERRED-STOCK-CURRENT>              820
<CAPITAL-LEASE-OBLIGATIONS>         12,037
<LEASES-CURRENT>                     1,355
<OTHER-ITEMS-CAPITAL-AND-LIAB>     530,625
<TOT-CAPITALIZATION-AND-LIAB>    1,436,961
<GROSS-OPERATING-REVENUE>          760,249
<INCOME-TAX-EXPENSE>                19,907
<OTHER-OPERATING-EXPENSES>         679,770
<TOTAL-OPERATING-EXPENSES>         699,677
<OPERATING-INCOME-LOSS>             60,572
<OTHER-INCOME-NET>                   1,970
<INCOME-BEFORE-INTEREST-EXPEN>      62,542
<TOTAL-INTEREST-EXPENSE>            30,329
<NET-INCOME>                        32,213
<PREFERRED-STOCK-DIVIDENDS>            751
<EARNINGS-AVAILABLE-FOR-COMM>       31,462
<COMMON-STOCK-DIVIDENDS>            25,551
<TOTAL-INTEREST-ON-BONDS>           24,912
<CASH-FLOW-OPERATIONS>             106,600
<EPS-PRIMARY>                         1.46
<EPS-DILUTED>                            0