June 16, 2011. The amount of solar energy capacity installed in the U.S. increased 66 percent in the first quarter as panel prices fell and developers took advantage of expiring government incentives. Developers installed 252 megawatts of photovoltaic power systems in the first quarter, compared with 152 megawatts a year earlier, according to a report released by the Washington- based Solar Energy Industries Association and GTM Research. Commercial and government projects accounted for 59 percent of the installations, compared with 44 percent a year earlier. Residential projects were 28 percent and the remaining 13 percent came from utility-scale plants. The cost of installing solar power is falling, driven by lower costs for components, greater economies of scale and streamlined development and installation, the report said. Prices of solar panels in the first quarter fell about 7 percent from a year earlier. First-quarter installation volume also increased after developers rushed to break ground on projects before the end of 2010 when a U.S. Treasury grant incentive program was set to expire. That program, which reimburses 30 percent of the costs of building solar systems, was extended in December until the end of 2011.