In 2005, the City of Aspen set a goal to purchase 75% of the city government's energy from renewable sources by 2010. As of December 2006, Aspen had accomplished its goal to provide 75% non-carbon electricity. The city has a new goal of powering 100% of the city-owned buildings with renewable sources by 2020.
27% of the electricity used by the City of Aspen comes from wind turbines located in Kimball, Nebraska. An additional 45% of the City's electricity comes from hydroelectric plants, with an additional plant, the Castle Creek Energy Center, planned to produce 8% of the City's energy needs.