JONATHAN FAHEYNEW YORK (AP) â¿¿ Duke Energy Corp. says its net income fell 42 percent in the first quarter because of cost overruns at a coal plant under construction in Indiana. The company said its underlying earnings grew slightly, though, despite a warm winter that reduced electric power demand and earnings at electric utilities nationwide. Duke's earnings were boosted by higher electric rates in the Carolinas, reduced costs, and higher power sales and rates in Brazil. The North Carolina-based power company said Friday that it earned $295 million, or 22 cents per share, in the three months ended March 31. That's down from $511 million, or 38 cents per share, a year ago. Its revenue edged down to $3.63 billion from $3.66 billion a year ago. Analysts expected revenue of $3.61 billion. Duke took a $420 million charge against earnings in the quarter to cover cost overruns at a coal plant under construction in Edwardsport, Ind. The cost of the project, which uses novel technology to turn coal into a gas before burning it, has risen to $3.36 billion from $1.99 billion. Duke reached an agreement on Monday with ratepayer groups in Indiana that will allow Duke to charge customers for some of the cost overruns, but not all of them. The agreement still needs to be approved by regulators, and some advocates in the state are opposing it. Adjusted to remove the effect of the plant costs, Duke earned 38 cents per share. Analysts expected 36 cents per share, according to FactSet survey. Duke shares rose 16 cents to close at $21.56 Friday. Its shares are near their 52-week high of $22.12. The first three months of the year were the warmest on record. Duke said Friday the number of heating degree days, an industry measure used to gauge energy demand, was the lowest ever for its service territory.