<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> UT
<LEGEND> This schedule contains summary financial information extracted from 
the Consolidated Balance Sheet and Statement of Consolidated Capitalization as 
of September 30, 1998 and the related Statements of Consolidated Operations, 
Retained Earnings (Deficit) and Cash Flows for the nine months ended September 
30, 1998 and is qualified in its entirety by reference to such financial 
statements. 
</LEGEND>
<CIK>      0000022606
<NAME>     Commonwealth Edison Company
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               SEP-30-1998
<BOOK-VALUE>                                  PER-BOOK 
<TOTAL-NET-UTILITY-PLANT>                   13,535,698
<OTHER-PROPERTY-AND-INVEST>                  2,115,166
<TOTAL-CURRENT-ASSETS>                       2,107,280
<TOTAL-DEFERRED-CHARGES>                             0<F1>
<OTHER-ASSETS>                               4,670,506
<TOTAL-ASSETS>                              22,428,650
<COMMON>                                     2,677,951
<CAPITAL-SURPLUS-PAID-IN>                    2,208,027
<RETAINED-EARNINGS>                            142,989
<TOTAL-COMMON-STOCKHOLDERS-EQ>               5,028,967
<PREFERRED-MANDATORY>                          157,118
<PREFERRED>                                    506,808
<LONG-TERM-DEBT-NET>                         5,782,824<F2>
<SHORT-TERM-NOTES>                                   0<F1>
<LONG-TERM-NOTES-PAYABLE>                            0<F2>
<COMMERCIAL-PAPER-OBLIGATIONS>                       0<F1>
<LONG-TERM-DEBT-CURRENT-PORT>                   83,304
<PREFERRED-STOCK-CURRENT>                       17,801
<CAPITAL-LEASE-OBLIGATIONS>                    401,288
<LEASES-CURRENT>                               177,504
<OTHER-ITEMS-CAPITAL-AND-LIAB>              10,273,036<F3>
<TOT-CAPITALIZATION-AND-LIAB>               22,428,650
<GROSS-OPERATING-REVENUE>                    5,576,132
<INCOME-TAX-EXPENSE>                           280,392<F4>
<OTHER-OPERATING-EXPENSES>                   4,477,355
<TOTAL-OPERATING-EXPENSES>                   4,769,304
<OPERATING-INCOME-LOSS>                        806,828
<OTHER-INCOME-NET>                            (16,149)<F4><F5>
<INCOME-BEFORE-INTEREST-EXPEN>                 802,236
<TOTAL-INTEREST-EXPENSE>                       339,879
<NET-INCOME>                                   462,357
<PREFERRED-STOCK-DIVIDENDS>                     43,062
<EARNINGS-AVAILABLE-FOR-COMM>                  419,295
<COMMON-STOCK-DIVIDENDS>                       257,082
<TOTAL-INTEREST-ON-BONDS>                            0<F6>
<CASH-FLOW-OPERATIONS>                       1,070,864
<EPS-PRIMARY>                                        0<F6>
<EPS-DILUTED>                                        0<F6>
<FN>
<F1> This item is not disclosed as a separate line item on the Consolidated
     Balance Sheet.
<F2> $1,049,479 thousand of notes is included in LONG-TERM-DEBT-NET.
<F3> Includes $350,000 thousand of Company-obligated mandatorily redeemable
     preferred securities of subsidiary trusts holding solely the Company's 
     subordinated debt securities.
<F4> A tax benefit of $11,557 thousand related to nonoperating activities is
     included in INCOME-TAX-EXPENSE.
<F5> Includes $22,283 thousand of provision for preferred securities dividends 
     of subsidiary trusts holding solely the Company's subordinated debt 
     securities.
<F6> This item is not disclosed as a separate line item on the Statement of
     Consolidated Operations.
</FN>
        

</TABLE>