Denver ? A company that supplies power to rural electric cooperatives in four Western states announced Monday that it will buy electricity from a new wind farm on Colorado’s eastern Plains.

The wind farm — to be built near Burlington — will supply enough electricity to power up to 14,000 households served by Tri-State Generation and Transmission Association Inc. A subsidiary of Duke Energy, one of the nation’s largest power generators, will build the farm and then sell the power to Tri-State for 20 years.

It’s the first large wind power deal for Tri-State, based in suburban Denver, which supplies power to 44 electric cooperatives in Colorado, Nebraska, New Mexico and Wyoming. The co-ops provide power to about 1 million people who live on farms and ranches as well as towns and suburban neighborhoods.

The 51-megawatt wind farm, expected to be completed by the end of 2010, will have 34 turbines spread across 6,000 acres. Tri-State said about 150 people will be needed to build it and four to eight full-time technicians will maintain it.

Terms of the deal between the two companies weren’t disclosed, although Wouter T. Van Kempen, president of Charlotte, N.C.-based Duke Energy Generation Services, said the construction costs were “north of $100 million.”

Tri-State, a partner in a controversial plan to build a new coal-fired power plant in southwest Kansas, has come under criticism for not moving quickly enough to expand its supply of renewable energy. Colorado regulators are also considering increasing oversight over Tri-State’s plans for future power generation.

Currently only 1 percent of Tri-State’s power comes from wind and solar. Power from the new wind farm and a solar plant planned for Cimarron, N.M., will take it to 3 percent. By contrast, the state’s largest utility, Minneapolis-based Xcel Energy, gets 10 percent of its power from renewable resources. It started buying wind energy a decade ago using voluntary contributions from customers.

A law passed by voters and later toughened by lawmakers will require Tri-State to get 10 percent of its energy from renewable sources by 2010. Xcel will need to increase its portfolio to 20 percent.