Net income rose to $465 million, or 37 cents per share, from $357 million, or 28 cents per share, a year earlier.
Excluding one-time items, discontinued operations and the market value of its trading portfolio, earnings per share rose to 35 cents from 30 cents a year ago.
On that basis, the earnings beat analysts' consensus forecast for earnings of 31 cents per share, according to Reuters Estimates.
Revenues rose to $3.34 billion from $3.04 billion.
Duke's commercial power business, which owns about 8,100 megawatts of electricity generation, saw earnings surge to $146 million from $13 million a year earlier. That gain was helped by an increase in the value of its trading positions, which offset higher expenses from plant maintenance.
Duke's electricity and gas utility operations posted a jump in earnings to $637 million from $574 million last year.