Exactly how much is Vail Resorts Inc. paying to offset its energy use with renewable-energy credits?

The answer, my friend, is blowing in the wind.

The company on Tuesday announced a plan to offset 100 percent of its energy use by purchasing nearly 152,000 megawatt-hours of wind energy. The deal, brokered by Boulder-based Renewable Choice Energy Inc., calls for the company to purchase renewable-energy certificates and doesn't mean the resort will actually be powered by wind.

Over the past few years, the market for wind energy has grown tenfold, fueled largely by companies such as Vail, Whole Foods Market, Starbucks and Safeway. The companies buy renewable-energy certificates from brokers who buy power from far-flung wind farms that then return the power to the national grid.

The process allows companies that may not otherwise have the option of buying wind energy - either because it is not available from the local utility or because they have multiple locations served by different providers - to do so.

Companies such as Renewable Choice Energy act as matchmakers in the process, pairing willing buyers with wind-farm operators. For their part, the brokers profit by negotiating a portion of the fee for themselves.

Quayle Hodek, chief executive of Renewable Choice, said the company's main competitors are utilities that also offer the credits.

"A lot of our clients chose us because we are not the monopoly fossil-fuel company. We are still a pure and simple renewable-energy provider," he said.

Unlike residential surcharges for similar renewable programs, the prices corporate buyers pay are rarely made public because each company negotiates its own rates and can get discounts based on the size and length of the contract.

A report prepared for the American Wind Energy Association in 2004 indicated a lack of transparency in the certificate- trading market.

"In places where it is a voluntary contract, the market is less transparent because they don't have to disclose what they're paying," said Kathy Belyeu, a spokeswoman for the group.

Industry experts estimate that Vail is probably paying a wind- power premium of less than a cent per kilowatt-hour. The average cost for one kilowatt-hour of conventional, nonrenewable energy is roughly 8.9 cents for an Xcel Energy customer. One thousand kilowatts equal one megawatt.

Smaller players or those who want their wind credits to come from a specific source could end up paying as much as 2 cents more per kilowatt-hour than if they bought conventional power, they said.

The University of Denver earlier this year said it would pay $81,000 for 15,000 megawatt- hours of wind energy, offsetting 10 percent of its energy use.

One expert believes that the increased interest in renewable energy could lead to the creation of a national market for energy certificates. Such a market would create more transparency in the process.

"There is an opportunity to forge a national market for renewable-energy credits," said Rich ard Sandor, chairman and chief executive of the Chicago Climate Exchange, a national market for emissions credits.

The process so far has been hampered by the regional nature of the process, but Sandor believes that increased focus on climate change and energy prices will help support such an exchange in the next few years.

Hodek agreed.

"It's uppermost in the public's mind," he said. "I think Colorado has a chance to take a national role."

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152,000
Megawatt-hours of wind-generated power Vail Resorts has agreed to purchase

100%
Portion of its usage that Vail Resorts says will be from wind power

8.9
Cost, in cents, for one kilowatt-hour of electricity from Xcel Energy

$81,000
What the University of Denver says it is paying for 15,000 megawatt-hours of power, about 10 percent of its usage