The largest utilities in Massachusetts have signed long-term contracts to buy wind-generated electricity at prices below the cost of most other sources, including coal and nuclear.

 

The contracts filed jointly with state utilities regulators by National Grid, Northeast Utilities, which owns NSTAR and Western Massachusetts Electric and Unitil would buy 565 megawatts of electricity from six planned wind farms in Maine and New Hampshire, or enough to power about 170,000 homes, according to a statement from the state Executive Office of Environmental Affairs.