Windwas the number one source of power for new electric capacity installed in 2015,recapturing that crown from natural gas, according to the American Wind EnergyAssociation's latest "U.S. Wind Industry Annual Market Report,"released April 12.

The report, a broad overview of wind developments in 2015,found 8,598 MW of capacity from utility-scale wind turbines added in 2015,which was 41% of all capacity installed. The contribution of wind was higherthan solar at 28.5% and natural gas at 28.1%.

While 2012 was the first year AWEA reported wind overtakingother energy sources in terms of new energy installations, natural gas was theleader in 2014, providing 44% of new electric generating capacity, compared to24% from wind, according to AWEA's 2014 report.

2015 also saw the most electricity generated by wind in oneyear in U.S. history, with 191 million MWh, equivalent to 16 nuclear reactors,AWEA said.

The report's numbers support the continued importance of taxcredits for the wind industry. Much of the surge in wind turbine installationsin 2015 is explained by the expiration of the wind production tax credit at theend of 2014, according to AWEA Manager for Industry Data and Analysis JohnHensley. Many of the wind projects that raced toqualify for that credit were completed in 2015. The tax credit was extended forfive years by Congress in late 2015.

But Hensley also stressed that "we saw a lot ofcompanies that see value in the low cost of wind" even without the tax credit.AWEA has identified agrowing trend of corporate, non-utility entities buying more and more windthrough long-term power purchase agreements.

Long-term contracts in general are the dominant force forthe development of wind projects. Of the 8,598 MW of new wind in 2015, 59% werecontracted under power purchase agreements, according to the report.

Mostpower purchase agreements were for wind projects clustered in Texas, Oklahomaand Kansas, but there were also projects in California, South Dakota, New York,Michigan and North Carolina, among other places.

There wasalso diversity among the utilities and parties on the other side of theseagreements. There were several examples of entities in regions not known forwind power signing up to use wind energy through contracts, according to AWEAResearch Analyst Hannah Hunt."We really saw the wind industry grow further into other reaches ofthe country" in 2015, she said. For example,last year Florida regulators approved an agreement for subsidiary utilityGulf Power Co. topurchase 180 MW of wind from FirstReserve Corp.'s Kingfisher Wind Farm in Oklahoma. That approvalmarked the first power purchase agreement for the Florida Public ServiceCommission, AWEA said.

Geography did have a significant impact on wind's popularityin 2015 and preceding years. In the Mid-Atlantic and Southeast, natural gas wasbigger than wind for new capacity. From 2011 to 2015, 59% of all new capacityin the Mid-Atlantic and 89% in the Southeast were from natural gas-firedplants. But in the Pacific Northwest, the Great Plains states and the Midwest,wind provided 59% or more of new capacity over that period from 2011 to 2015.

Thethree companies that own the most wind capacity in the U.S. are subsidiaries NextEra EnergyResources LLC and NextEra Energy Partners with a combined 11,548 MW,Iberdrola SAsubsidiary Iberdrola RenewablesLLC with 5,645 MW and BerkshireHathaway Energy with 5,055 MW, AWEA said. The company with thebiggest jump in AWEA's rankings of wind-owning companies was , which aggressivelyacquired several wind assets and now owns 2,345 MW when the holdings of itsTerraForm Power Inc.yieldco are included.