Uncertainty about whether the credit would be extended put projects on hold. "We didn't expect it to be a great year," said Kathy Belyeu, a spokeswoman for the American Wind Energy Association. "The fact that the credit expired meant that there weren't any projects built in the first three quarters of the year."

In 2004 US wind generation capacity rose six percent, or 389 megawatts, to a total of 6740 MW, or enough power to serve 1.6 million households. General Electric Co. waited until late in the year to announce it had more than $1.3 billion in new orders and commitments for wind turbines.

Growth was slower than that in 2001 and 2003. Each of those years the US added nearly 1,700 MW of capacity.

One of AWEA's top priorities now is lobbying for a tax credit that's good for more than two years.

"The short-term duration of the federal production tax credit and its repeated expirations, three in the past six years, are keeping this industry from reaching its potential to supply the nation with clean, domestic electricity," said Randall Swisher, AWEA's director.

AWEA expects 2,000 MW of new wind power capacity to be added in 2005.

Wind power makes up less than 1 percent of the US power mix, but it is the fastest growing alternative energy. The Energy Department has set a goal for the United States to obtain 5 percent of its electricity from wind by 2020.