On per-share basis, earnings fell to 17 cents per share, in the April-to-June period, from 19 cents per share, a year earlier, the Edmonton, Alberta-based company said in a statement on July 25.
Overall, net income was flat at 20 million.
On an adjusted basis, earnings were 7 cents per share, missing the 23-cents analysts predicted on average.
Revenue fell to $240 million from $321 million year over year.
Capital Power said its financial performance during the second quarter was affected by seasonally low power prices in Alberta and lower power generation from its Sundance and Genesee 3 operations, but expects its operating margin to grow.
"While we are disappointed with this quarter's financial performance, the fundamentals of our business and the additions to our solid asset base continue to strengthen the outlook for the Company," Chief Executive Officer Brian Vaasjo said in the statement.
Capital Power said its quarterly dividend will go up 7.9 percent to 34 cents per common share, starting with the next payment on Oct. 31.
Shares closed down 2.2 percent at C$25.75 in Toronto on July 25, paring this year's gain to 21 percent.