Yale Environment 360: The city of Houston has agreed to purchase half its electricity from renewable energy sources, a step that makes the Texas city the nations largest municipal buyer of green energy. In a contract signed with Reliant Energy, Houston committed to buying more than 140 megawatts of renewable power from July 1, 2013 through June 30, 2015, locking in nearly 623,000 megawatts of clean power annually. According to city officials, the government committed $2 million less than 1 cent per kilowatt-hour ...