Approximately 1.2 gigawatts worth of wind turbines were installed in the U.S. in the second quarter, according to the American Wind Energy Association, bringing the total for the first half of the year to 4 gigawatts.

That's far higher than the 2.9 gigawatts added in the first half of 2008, when credit was a little easier to come by. The total wind capacity in the U.S. is now 29.440 gigawatts, enough to reduce the carbon output of the utility sector by two percent. The economic downturn had made some analysts worried that the growth of wind would subside.

Iowa is now number three in wind installations with 3 gigawatts. Installations in Missouri grew by 90 percent. Wind manufacturers are also beginning to push for offshore wind farms as well as trying to popularize small wind turbines. In April, General Electric invested in Southwest Windpower, the leader in small turbines. Minnesota 2020 says that that state will need 4,000 megawatts more of wind to hit the 25 percent renewable mandate by 2020.

But don't get too happy, warns the AWEA.

"The numbers are in, and while they show the industry has been swimming upstream, adding some 4,000 MW over the past six months, the fact is that we could be delivering so much more," said AWEA CEO Denise Bode in a prepared statement. "Our challenge now is to seize the historic opportunity before us to unleash this entrepreneurial force and build up an entire new industry here in the U.S. that will create jobs, avoid carbon, and strengthen our energy security. To achieve that, Congress and the Administration must pass a national Renewable Electricity Standard (RES) with strong early targets."   

The number to watch for the rest of the year is 8,358 megawatts. That's how much was installed in the U.S. in 2008.