For the third quarter, the company posted net income of $594 million, up from $472 million a year earlier. Earnings per share fell to 85 cents from $1.06 as shares outstanding increased 57 percent, due in part to the Progress deal.

Excluding charges to integrate Progress and other one-time items, Duke earned $1.47 per share. By that measure, analysts expected $1.45, according to Thomson Reuters I/B/E/S.

Chief Executive Jim Rogers said Duke is "on track" to hit its 2012 earnings forecast of $4.20 to $4.35 per share, and the integration of the two companies is progressing.

"I've pretty much stopped speaking outside the company," Rogers said in an interview. "I've been focused internally trying to integrate these two teams. We're on the way."

The integration has been challenged by the way Rogers was put into his current role.

Shortly after the $18 billion Progress Energy deal closed in July, the combined company's new board said Progress Chief Executive Bill Johnson had resigned and would not be taking the top job at the combined company as had been planned.

Rogers, Duke's CEO as the merger was negotiated, was asked to stay at the helm.

The swap left many legacy Progress employees uneasy about the change and about Rogers. Rogers told North Carolina regulators that Duke's board had grown worried about Johnson's "autocratic" management style and ability to lead such a large organization.

Johnson now runs the Tennessee Valley Authority.

Rogers, 65, says he has no plans to leave Duke any time soon.

"I'm serving at the pleasure of the board and focused on getting these two companies to come together," he told Reuters. "Sixty-five, in my judgment, is the new 55."

Charlotte, North Carolina-based Duke is the largest U.S. power company, with 57,000 megawatts of generating capacity and 7.1 million electricity customers in North Carolina, South Carolina, Florida, Indiana, Kentucky and Ohio.

Duke is also the second-largest U.S. operator of nuclear power plants.

Shares of Duke closed Wednesday at $62.94, down nearly 5 percent this year.

(Reporting By Ernest Scheyder; Editing by Gerald E. McCormick and John Wallace)

By Ernest Scheyder