Colorado's biggest utility asked for bids this year for up to 150 megawatts of wind power projects. So far, it has received 2,400 megawatts of acceptable bids from 16 wind project developers - more than 15 times the capacity that Xcel sought.
And for 25 megawatts of solar projects, Xcel received bids amounting to 400 megawatts from 18 solar developers, or 16 times as much as it asked for, according to filings with the Public Utilities Commission.
"What this bidding information tells us is what we know: Companies are ready to take advantage of Colorado's wind and solar resources, and they are putting solid bids on the table," said Leslie Glustrom, a founder of the nonprofit group Clean Energy Action.
"This is the new energy economy, this is where our jobs will be, and we will build the state's economy around it," Glustrom said.
Xcel is negotiating with the bidders and will select the projects in coming months, said spokesman Mark Stutz.
The PUC still would have to approve the contracts.
Xcel expects the projects to be in service by Dec. 31, 2012.
Xcel initially received bids for wind projects worth 2,785 megawatts, but rejected 400 megawatts for various reasons.
Stutz said Xcel considers factors such as cost, location, access to transmission and the developer while evaluating bids.
One megawatt of solar or wind power serves the average electricity needs of 250 to 350 households.
Xcel also plans to seek bids for more wind and solar projects next year, in keeping with its resource plan.
Stutz said Xcel will ask for 675 megawatts worth of wind and solar projects in addition to up to 600 megawatts of large-scale solar projects that allow storage, such as concentrating solar power plants.
Since voters passed a ballot measure in 2004 to hike the renewable energy mix in electricity sales, and the state legislature doubled that goal in 2006, Xcel has been ramping up wind and solar power in its system.
Today, Xcel has almost 1,100 megawatts of wind on its system in Colorado, with the total system capability being 7,715 megawatts.
Wind and solar account for more than 10 percent of its electricity sales, and Xcel hopes to hit 20 percent by 2015 - five years ahead of target.
Renewable energy critic Stan Lewandowski - general manager of Intermountain Rural Electric Association, the state's largest rural electric cooperative serving more than 134,000 customers - says wind and solar are intermittent, requiring backup power from natural gas- or coal-fired plants and adding to utility costs.
"That's a fair assessment," Stutz said. "Wind and solar still remain, as of today, intermittent generating resources that require some degree of backup generation that's fossil fuel."
Xcel is studying the cost of integrating wind power into its system, he said, and the study will be filed with the PUC next year.