Duke Energy Corp., the nation's largest electric utility by market value, reported stronger-than-expected earnings for the third quarter, but company executives said the outlook for strong economic growth in the U.S. is dim.

The company said more customers signed up for service, which is a hopeful sign, but demand for electricity from homes and businesses has been weak. Jim Rogers, Duke's CEO, said in an interview that the company is operating under the expectation that electricity demand, excluding the effects of weather, will grow at a rate of less than 1 percent.

He said that with slow population growth in the U.S., the financial crisis in Europe, and diminished expectations of growth in China, "People look around and see there's no part of the world that can really juice growth."

"We are in a slow growth period," he said.

Still, Duke reported solid third quarter results Thursday, the company's first quarterly results since acquiring Progress Energy in late June to become the largest U.S. utility. The Charlotte, N.C.-based company serves 7 million customers in the Carolinas, Florida, Indiana, Kentucky and Ohio.

Duke reported earnings of $594 million, or 85 cents per share, on revenue of $6.72 billion. The company said it earned $1.47 per share when it excluded $457 million in deal-related costs, a $180 million increase in the costs it must pay to complete a new coal plant in Indiana and other unusual items.

Analysts surveyed by FactSet had expected Duke to earn an adjusted $1.44 per share on revenue of $6.79 billion.

Duke Energy Corp. shares rose 56 cents, to $63.50 each, in morning trading.

Andy Smith, an analyst at Edward Jones, welcomed the company's customer growth in both its Progress and Duke territories, and said he expects company results to improve in the coming months as it seeks to increase rates in the Carolinas and begins to realize savings from the merger.

"It looks like a pretty solid quarter," Smith said.

Duke was allowed to charge customers in the Carolinas higher rates in the quarter, which helped results. But milder weather in its service territory reduced demand for electricity to run air conditioners.

Sales of electricity to industrial customers declined 1.1 percent in the quarter. Duke CFO Lynn Good said its automotive customers were operating at full strength but its metals customers were pulling back. "The economy has been sluggish," she said in an interview.

Duke's commercial power division, which generates electricity and sells it into wholesale markets in the Midwest, suffered from lower wholesale power prices, especially in Ohio.

Duke also owns and manages power plants in Latin America. Those results suffered from unfavorable currency exchange rates.

The company said it remains on track to post full-year adjusted earnings of $4.20 to $4.35 per share.

A few major issues face the company in the coming months, however. The company is being investigated by the North Carolina Utilities Commission over the way it handled changes in executive leadership after the merger with Progress Energy. Jim Rogers was to cede the CEO job to former Progress chief Bill Johnson. Hours after the merger was completed, however, Johnson was ousted and Rogers was give the CEO job back.

Johnson was picked this week to run the Tennessee Valley Authority, a government-owned corporation that provides electricity to 9 million people in parts of 7 states in the Southeast, beginning in January.

Duke said it is working with the commission on a resolution to the commission's objections.

At the same time, the company is asking the commission to allow it to raise rates for customers in the Progress service territory by $359 million, the first such increase in 25 years. Hearings are set for March. Analysts worry that the controversy over the executive changes at the company will make the commission less inclined to grant Duke all of the rate increase it is requesting.

Also, the company's idled Crystal River nuclear plant in Florida, acquired in the Progress merger, is facing enormous costs to repair cracks in its most important structure. Investors are waiting for a decision by Duke over whether to repair the plant or shut it permanently.