While lawmakers offer numerous proposals to lower energy prices and slow global warming, Congress still hasn't taken a small step to help a clean source of power - wind generators.

Electricity production from wind farms soared 45 percent last year and now powers about 4.5 million U.S. homes without emitting any greenhouse gases that contribute to global warming. But industry representatives say further growth is threatened because a tax credit they rely on expires in December.

"We're at a situation today when projects for 2009 are being put on hold," said Greg Wetstone of the American Wind Energy Association. "Here's something we can do right now that can have huge payoffs ... to promote major greenhouse gas reductions."

With the help of the production tax credit, electricity generated from wind increased from 2,600 megawatts in 2000 to 16,800 megawatts in 2007. Wind powered an additional 500,000 U.S. homes annually during this period, and windmills spin in 35 states.

Supporters say the current tax credit of 2.1 cents per kilowatt-hour makes electricity generation from wind, solar and other renewable sources cost-competitive with natural gas, coal and nuclear power. Wind generation continues to be the fastest growing sector of green power.

But large wind farms cost tens of millions to build and take years to plan and develop. Companies need assurance on the tax credit now to secure financing to buy equipment and negotiate prices they charge for their electricity, Wetstone said.

Wind power enjoys widespread support. Even the National Mining Association, which represents coal companies that provide about half the nation's electricity, doesn't oppose the tax credits, spokesman Luke Popovich said.

But Congress struggles to fund a one-year extension that will cost $3.5 billion to pay wind generators the credit for 10 years. The House passed the extension in May, but the Senate has failed three times to approve it this year.

"Now it's time to take quick action and extend the credit because investors need certainty about tax policy before putting additional money into wind energy," Sen. Chuck Grassley, R-Iowa, said last month after the House vote.

On Tuesday, the Senate failed again to approve wind power's tax credit that was contained in a larger package of tax provisions.

"The general agreement among everyone is: 'Look, Congress is not going to let these things expire,' " said Bill Wicker, spokesman for the Senate Energy and Natural Resources Committee. "Unfortunately, there aren't a lot of extra dollars laying around."

The most recent proposal would extend the wind tax credit for only an additional year, not the long-term incentive that wind proponents say is needed to grow dramatically.

Windmills could provide up to 20 percent of U.S. electricity demand by 2030, up from 1 percent today, according to an Energy Department report released in May. The renewable power source could grow rapidly without major technology breakthroughs and could support nearly 500,000 jobs by 2030, the report said.

But failure to pass long-term tax credits slowed the wind business in the past, said Vic Abate, vice president of renewable at GE Energy, the largest U.S. manufacturer of wind turbines. When the tax credit lapsed in 2002 and 2004, few U.S. wind power projects were added, he said.

"This isn't about what could happen - that's pretty clear," Abate said. "If the (tax credit) doesn't happen, this equipment will go to other parts of world."

GE has six wind turbine plants across the globe, including facilities in Pensacola, Fla., and Greenville, S.C. With uninterrupted growth, the U.S. could overtake Germany next year to become the leader in wind power production, Abate said. More than 6 percent of Germany's electricity comes from wind.

But many countries support renewable energy, and manufacturers will build plants in the regions most friendly to wind power, he said. Transportation costs are enormous for turbines with blades as long as football fields, he said.

"Everybody is looking for an alternative to traditional fuels," Abate said. "(Wind power) is really on the cusp of becoming a tremendous growth engine and we could see it growing for a decade plus."

Reach Doug Abrahms at dabrahms@gns.gannett.com