Duke Energy Corp., which plans to buy Progress Energy Inc. to become the nation's largest utility owner, said first-quarter profit fell 42 percent after a regulatory settlement in Indiana increased costs and mild weather reduced heating demand.

Earnings fell to $295 million, or 22 cents a share, from $511 million, or 38 cents, a year earlier, Charlotte, N.C.-based Duke said Friday in a prepared statement. Excluding the Indiana settlement and other one-time items, per-share profit was 2 cents more than the 36-cent average of 10 analysts’ estimates compiled by Bloomberg.

The Indiana settlement, announced April 30, clipped results by 20 cents. It resolves a dispute over cost overruns at a $3.3 billion coal-fueled power plant in Edwardsport expected to begin operation this year. Duke agreed that customers will pay only $2.6 billion of the plant cost.

In North Carolina, where Duke has the most customers, the first quarter was the warmest in 22 years, according to the National Climatic Data Center. Lower heating demand cut results by 4 cents a share, Duke said. Higher utility rates in North and South Carolina added 3 cents to profit.

Sales fell 0.9 percent to $3.63 billion. Chairman and CEO Jim Rogers affirmed a forecast for 2012 adjusted profit of $1.40 to $1.45 a share.

Included in the forecast are lower operating earnings of 2 cents a share that will result from the Indiana plant settlement, Chief Financial Officer Lynn Good said.

Duke needs both federal and state approvals to close the $16.5 billion Progress transaction, revised after the Federal Energy Regulatory Commission rejected the initial mitigation plan because of anti-competition concerns. Progress said Thursday it expects the merger to close by July 1.

The deal would combine North Carolina’s largest utilities and create the second-largest U.S. nuclear power plant operator. Progress, based in Raleigh, N.C.,  reported net income of $150 million, or 51 cents a share, on sales of $2.1 billion Thursday.

Duke’s earnings were released before regular trading began on U.S. markets. Duke shares fell 0.4 percent, to $21.40 each, Thursday. Progress rose 0.8 percent, to $53.99.

Exelon Corp., based in Chicago, is currently the largest U.S. utility owner and the largest operator of nuclear plants.