<PAGE>
 
                                                                    Exhibit 12.1
                                                                                
                                        

                     Duquesne Light Company and Subsidiary

               Calculation of Ratio of Earnings to Fixed Charges
                             (Thousands of Dollars)

<TABLE>
<CAPTION>
 
                                                                                     Year Ended December 31,
                                                                    ----------------------------------------------------------
                                                                      1997             1996       1995       1994       1993
                                                                    ---------        --------   --------   --------   --------
<S>                                                                 <C>              <C>        <C>        <C>        <C>
FIXED CHARGES:
  Interest on long-term debt                                        $ 81,592         $ 82,505   $ 89,139   $ 94,646   $102,938
  Other interest                                                         752            1,632      2,599      1,095      2,387
  Monthly Income Preferred Securities dividend requirements           12,562            7,921          -          -          -
  Amortization of debt discount, premium and expense - net             5,828            5,973      6,252      6,381      5,541
  Portion of lease payments representing an interest factor           44,208           44,357     44,386     44,839     45,925
                                                                    --------         --------   --------   --------   --------
        Total Fixed Charges                                         $144,942         $142,388   $142,376   $146,961   $156,791
                                                                    --------         --------   --------   --------   --------
 
EARNINGS:
  Income from continuing operations                                 $141,820         $149,860   $151,070   $147,449   $144,787
  Income taxes                                                        73,838*          83,008*    92,894*    84,191*    77,237*
  Fixed charges as above                                             144,943          142,388    142,376    146,961    156,791
                                                                    --------         --------   --------   --------   --------
        Total Earnings                                              $360,601         $375,256   $386,340   $378,601   $378,815
                                                                    --------         --------   --------   --------   --------
 
RATIO OF EARNINGS TO FIXED CHARGES                                      2.49             2.64       2.71       2.58       2.42
                                                                    ========         ========   ========   ========   ========
 
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  Duquesne's share of the fixed charges of an unaffiliated coal
supplier, which amounted to approximately $2.7 million for the twelve months
ended December 31, 1997, has been excluded from the ratio.

*Earnings related to income taxes reflect a $17.0 million, $12 million, $13.5
million, $13.5 million and $10.4 million decrease for the twelve months ended
December 31, 1997, 1996, 1995, 1994 and 1993, respectively, due to a financial
statement reclassification related to Statement of Financial Accounting
Standards No. 109, Accounting for Income Taxes.  The ratio of earnings to fixed
charges, absent this reclassification, equals 2.61, 2.72, 2.81, 2.67 and 2.48
for the twelve months ended December 31, 1997, 1996, 1995, 1994 and 1993,
respectively.