The Colorado Public Utilities Commission on Wednesday said Xcel can begin seeking bids to acquire up to 500 megawatts of renewable- energy resources.

Xcel officials said wind power would most likely make up most of the new energy capacity. The company already has 250 megawatts of wind-generating capacity.

If it is able to add 500 more megawatts, Colorado would be the third-largest generator of wind energy behind California and Texas, Xcel officials said.

The company currently generates 4 percent of Colorado's power through renewable-energy resources, much of it from wind farms. That would jump to 10 percent under Xcel's plan.

"We are very pleased that the commission approved our request to greatly expand our renewable-energy resources, and we will issue our request for proposals shortly," Fred Stoffel, Xcel Energy vice president of policy development, said in a statement Thursday.

Renewable-energy advocates praised Xcel's plan but said the company should be doing more.

"They're moving in the right direction. However, our concern is that they're not moving quickly enough," said Manolo Gonzalez-Estay of Coloradans for Clean Energy.

The group is trying to get an initiative on the November ballot that would force Xcel and other energy providers in Colorado to generate more of their energy from renewable sources. Xcel opposes the initiative.

Xcel spokesman Mark Stutz said Xcel's plan to add 500 megawatts of wind power capacity is contingent on Congress renewing a tax credit for the energy source.

The tax credit has expired, but Xcel officials expect it to be renewed and extended through the end of 2006, Stutz said. Wednesday's PUC decision allows Xcel to proceed with its plan while it waits for action in Washington.

The credits could be worth up to $271 million to contractors who deliver the new wind power to Xcel, Stutz said.

The company hopes to have all the new wind energy on line by the end of 2006.