The utility National Grid announced Friday that it has agreed to buy electricity from the nation's first wind farm, planned off the coast of Cape Cod, The Associated Press reports.
Under the 15-year contract, National Grid would pay 20.7 cents per kilowatt hour starting in 2013 for electricity purchased from the 130-turbine Cape Wind project in Nantucket Sound.
The price would go up by 3.5 percent annually to keep pace with inflation.
The cost of electricity from conventional sources is about 9 cents per kilowatt hour. The utility said the deal will add about $1.50 the average customer's monthly electricity bill in 2013.
Massachusetts Energy and Environmental Secretary Ian Bowles said adjusted to 2010 dollars, and minus the renewable energy credit consumers pay the utility anyway, the deal puts Cape Wind's power at 12.6 cents per kilowatt hour.
He said that price is comparable to the price of natural gas at its peak two years ago. Given the trends in natural gas prices, Bowles said he believes the deal will ultimately save Massachusetts ratepayers money over the life of the deal.
"The price is much better than I expected," Bowles said.
The deal is considered crucial for financing a project estimated to cost at least $2 billion.
It must still be approved by state regulators.