NStar electric customers in Massachusetts will be able to buy renewable energy directly from wind farms - including one under development in Maine - under a newly approved billing option.

The state Department of Public Utilities approved the "NStar [NST] Green" program on Wednesday.

NStar's more than 1 million residential customers in eastern and central Massachusetts will be able to buy either half or all their electricity from wind farms in the Northeast. Customers would pay a small premium above current basic service rates.

The energy would come from either Maple Ridge Wind Farm in upstate New York, or from Kibby Mountain, a wind farm under development in Maine. NStar has signed two 10-year contracts to receive energy from the wind farms.

NStar is collaborating in the program with environmental organizations.