Idacorp ( IDA - Get Report), the holding company of Idaho Power and other subsidiaries, said its first-quarter earnings rose 10.4% from a year ago. The Boise, Idaho-based company earned $25.5 million, or 60 cents a share, compared with $23.1 million, or 55 cents a share, a year ago. Idaho Power, the company's regulated utility, contributed earnings of 59 cents a share compared with 51 cents a share a year ago. Analysts surveyed by Thomson First Call were expecting earnings of 56 cents a share in the most recent quarter. Hydroelectric generation contributed 62% of the Idaho Power's total system generation compared with 44% in 2005. Idaho Power was able to sell surplus energy, which tripled off-system sales revenue and volumes and significantly reduced net power supply costs. This helped in 7 cents a share benefit quarter-over-quarter. First-quarter revenue rose 39.5% to $273.6 million, topping analysts' estimate of $207 million. Operating profit rose 25.5% to $43.8 million, but operating profit margin declined 180 basis points to 16%. "We had a good quarter. Abundant water in the rivers has doubled the output from Idaho Power's hydro plants compared to a year ago, lowering the cost of production and tripling surplus sales for the benefit of customers and shareowners alike," the company said.