Xcel Energy, Colorado's largest utility, has filed a request with the Colorado Public Utilities Commission a three-year, 3.6 percent rate hike to cover the cost of upgrading pipelines.

The requested increase totals $113.8 million from 2013 to 2015.

The new rates would take effect in August, increasing bills for the average residential customer by 2.1 percent in 2013 and by 5.8 percent and 2.8 percent in the following two years.

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