Montgomery County is heading a group of local governments in buying wind-generated electricity, a move lauded by clean-energy advocates as a groundbreaking step toward reducing the nation's reliance on fossil fuels.

County Executive Douglas M. Duncan (D) announced yesterday that a buyers group consisting of Montgomery and Prince George's counties, as well as six county agencies and 11 municipalities, would purchase 5 percent of its electricity from Community Energy Inc., which will generate the power at wind turbines in West Virginia.

The decision represents the largest-ever purchase of wind power by local government buyers, said Mike Tidwell of the nonprofit Chesapeake Climate Action Network, who calculates that the environmental benefit is equivalent to the planting of 2.9 million trees.

"We think that the trend of green-power purchasing is going to grow in this region following the example of Montgomery County," said Matt Clouse, director of a program of the Environmental Protection Agency that encourages the use of nonpolluting, renewable sources of electricity.

The wind-power purchase, which will be effective July 1, might help Maryland and the region comply with the federal Clean Air Act. If the EPA agrees that the deal can be counted as part of a pollution-reduction plan, it would be the first time that the agency has recognized the use of wind power as a way of meeting federal air-quality requirements, said Debra A. Jacobson, an energy and environmental consultant who advised the county on the purchase.

Wind power is more expensive than conventionally generated electricity; officials estimated that the members of the buyers group will spend $575,000 more annually than they would have spent otherwise. But Montgomery, which spends about $3.7 million a year on electricity, plans to cover any losses by requiring county employees to turn off lights and power down computers and office equipment when not in use.

"We anticipate the savings to county government from increased energy conservation will offset the higher price of wind power," said Montgomery County Council member George L. Leventhal (D-At Large). Leventhal, whose council resolution ultimately resulted in the decision to purchase the wind power, said the county would have to spend $110,000 more per year for the energy but estimates savings of $250,000 through conservation.

James P. Keary, spokesman for Prince George's County Executive Jack B. Johnson, said Johnson was unable to attend yesterday's event because he and members of his staff were in New York meeting with bond rating companies. Keary said Prince George's will buy 5 percent of its local demand in wind energy, a switch that will cost the county $63,970 a year. "It's a lot of money, but to have cleaner air, the savings could be significant," Keary said.

The county spends about $5.5 million annually on electricity. Nearly $4 million is for county facilities; the rest pays for streetlights, traffic lights and other things.

Tidwell and Clouse spoke yesterday at a news conference at Duncan's office in Rockville. Representatives of the some of the other entities buying the wind power -- such as the Washington Suburban Sanitary Commission, Montgomery College, the Maryland-National Capital Park and Planning Commission and the city of College Park -- also attended the event.

Staff writer Ovetta Wiggins contributed to this report.