<Page>
                                                                      EXHIBIT 3


                         TransCanada PipeLines Limited
                                EARNINGS COVERAGE
                                DECEMBER 31, 2003

     The following financial ratios have been calculated on a consolidated basis
for the respective 12 month period ended December 31, 2003 and are based on
unaudited financial information. The financial ratios have been calculated based
on financial information prepared in accordance with Canadian generally accepted
accounting principles. The following ratios have been prepared based on net
income:

<Table>
<Caption>
                                                             DECEMBER 31, 2003
                                                             -----------------
                                                          
Earnings coverage on long-term debt(1)....................       2.79 times
Earnings coverage on long-term debt and
   First Preferred Shares(1)..............................       2.67 times
</Table>

(1)  The above ratios have been calculated without including the annual carrying
     charges relating to the equity component of TransCanada's outstanding
     preferred securities. If the equity component of the preferred securities
     were classified as debt, the entire carrying charges of the preferred
     securities would be included in interest expense and dividends. If these
     annual carrying charges had been included in the calculations, the earnings
     coverage on long-term debt would have been 2.64 times for the 12 month
     period ended December 31, 2003 and the earnings coverage on long-term debt
     and First Preferred Shares would have been 2.54 times for the 12 month
     period ended December 31, 2003.

     The following ratios have been prepared based on net income from continuing
operations:

<Table>
<Caption>
                                                             DECEMBER 31, 2003
                                                             -----------------
                                                          
Earnings coverage on long-term debt(2)....................       2.70 times
Earnings coverage on long-term debt and
   First Preferred Shares(2)..............................       2.59 times
</Table>

(2)  The above ratios have been calculated without including the annual carrying
     charges relating to the equity component of TransCanada's outstanding
     preferred securities. If the equity component of the preferred securities
     were classified as debt, the entire carrying charges of the preferred
     securities would be included in interest expense and dividends. If these
     annual carrying charges had been included in the calculations, the earnings
     coverage on long-term debt would have been 2.55 times for the 12 month
     period ended December 31, 2003 and the earnings coverage on long-term debt
     and First Preferred Shares would have been 2.45 times for the 12 month
     period ended December 31, 2003.