Aspen, Colorado, with a population of 7,000, has become the third municipality in the country, along with Burlington, Vermont, and Greensburg, Kansas, to receive all of its power from renewable sources. Its energy portfolio now consists primarily of wind power and hydroelectric, with smaller contributions from solar and geothermal.

The development reflects a decadelong effort made possible in part by a significant drop in the price of renewable energy and new government regulations that internalize some of the pollution costs of fossil fuels, making energy sources like coal increasingly uncompetitive. More than one-third of American coal plants have been shut down in the past six years and new carbon rules make it possible that no new coal plants will ever be built in the U.S.

Source: ThinkProgress.org