Aspen becomes third U.S. city to go 100 percent renewable energy

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The city of Aspen has become the third U.S. city to run on 100 percent renewable energy.

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The Colorado mountain town was already more than 75 percent along in its goal and achieved the full transition Thursday when it signed a contract with a wholesale energy provider.

The goal of 100 percent renewable energy was stated in the city's Canary Initiative that was launched 10 years ago.

Burlington, Vermont  and Greensburg, Kansas  were the first two cities to go to 100 percent renewable energy.