The City of Boulder purchases a portion of its electricity supply from wind power through Xcel Energy's Windsource program and Renewable Choice Energy, headquartered in Colorado. Boulder purchases approximately 470,000 kWh annually to provide clean power for its municipal buildings. Boulder also installed a solar water heating system with 128 thermal panels on one of its city-owned pools. The city now has 1,955 kilowatts (kW) of photovoltaics installed with an additional 349 kW planned. These efforts account for 3% of the city's electrical load.