When I posted a version of this map at CleanTechnica a few years ago, the U.S. was still in the thick tail of the wind boom that lasted from 2007  into 2010.  Illustrative of this is the fact that when I published the map in June 2009, 28,635 megawatts of wind power capacity was on the books. By end of that year, the U.S. added over 6 gigawatts in additional capacity—in the last half of the year alone—upping the total to 34,863.

But growth in wind power capacity slowed considerably in 2010. Through the end of September, the U.S. has 43,461 MW of cumulative wind capacity and 2011 is on pace to be the slowest year for new wind capacity since 2006. The sagging economy spawned two inter-meshed problems: the difficulties of securing project financing and taking advantage of federal tax incentives. But while we may see another dip in annual capacity added in 2011, 2012 could prove to be another big year.

With the Production Tax Credit set to expire at the end of 2012 and the political future uncertain for an extension, wind developers are in a race against the clock to get new wind farms built. As of September, 8,482 megawatts are under construction, according to the American Wind Energy Association. What happens after 2012 may be another story.

Image credits: 1. Wind Powering America ; 2. American Wind Energy Association