Four Vermont dairy farms are producing electricity for the utility, and two more are expected to be online by year’s end, Mr. Costello said. The utility hopes to add six more farms by 2010.

Residents and businesses that get their electricity from the program pay a premium of 4 cents a kilowatt hour above the typical rate of 12.5 cents. Most of that money goes to the farmers, who must purchase their own equipment, which can run up to $2 million per farm. Most farmers expect to make back their investment in 7 to 10 years.

The brothers who own Green Mountain Dairy, Bill and Brian Rowell, were looking to squeeze more profit from their farm, where they have 1,050 cows and have begun acquiring 600 heifers. Milk prices had dipped and they wanted another source of income.

They also thought that the huge amount of waste their cows produced could be used for something other than fertilizer. So they decided to give electricity a try, armed with about $750,000 in federal, state and utility company grants.

“We saw this as an economic and environmental management tool,” Bill Rowell said. “It’s helped to diversify our farm,” which was named the 2008 Vermont Dairy Farm of the Year.