The industry says the credit has helped wind account for 35 percent of all new U.S. power capacity in the last four years while making the zero-emissions source cost-competitive with coal and natural gas. A recent report from IHS Emerging Energy Research, an independent research group in Cambridge, Mass., said expiration would cause wind-power installations to decrease from 5.6 gigawatts a year since 2005 to 2.3 gigawatts a year from 2013 to 2016 and leave wind vulnerable to competition from low natural-gas prices.