Wind energy is blowing up a storm.

U.S. wind power grew 45 percent in 2007, the sharpest rise since the 1980s, as developers responded to a federal tax credit, a growing number of state renewable energy mandates and global warming concerns, the American Wind Energy Association said Thursday.

The industry installed 5,244 megawatts in 2007, accounting for 30 percent of all new electricity-generating capacity, the AWEA says. That's more than double the largest amount ever added and enough to power 1.5 million homes, says AWEA Executive Director Randall Swisher. U.S. wind power had been annually growing an average 30 percent the previous five years, he says.

"I think it signifies that wind will be an increasingly significant contributor to our electricity supply system," Swisher says, predicting that wind could provide 20 percent of U.S. power by 2020.

Wind now generates more than 1 percent of U.S. electricity, the AWEA says. That far surpasses other renewable energies — such as solar and biomass — except for large hydroelectric projects. The U.S. has been the world leader in wind energy growth the past three years, though the nation still trails Germany in total wind power.

Texas, by far, added the most wind capacity, at 1,618 megawatts, followed by Colorado, Illinois, Oregon and Minnesota, the AWEA says.

In Hawai'i there are operating wind farms at Hawi and South Point on the Big Island and at Kaheawa on Maui. Additional wind farms are planned for locations on O'ahu, Maui, Kaua'i and Lana'i.

The main reason for the robust growth is a federal tax credit of 2 cents per kilowatt hour of energy produced, says analyst Stow Walker of Cambridge Energy Research Associates.

The tax credit lowers a developer's costs to about 7 cents per kilowatt hour, placing wind costs on par with coal-fired plants.

Congress approved the tax credit in the 2005 energy bill, and it expires at the end of 2008. The three-year window has given turbine manufacturers confidence in a sustained market for their products, Swisher says.

By contrast, previous tax credits for wind power expired after a year, creating a boom-and-bust cycle from 1999 to 2004.

Although a proposal to further extend the tax credit was ultimately left out of the energy bill that Congress passed last month, Walker predicts lawmakers will extend the credit before it expires.

"Congress doesn't want a lack of confidence in the industry just as it's getting so big," he says.