NSTAR Electric Company is a regulated electric utility company. The Company serves residential, commercial and industrial customers in parts of eastern and western Massachusetts and owns solar power facilities. Its wholly owned subsidiary, Harbor Electric Energy Company (HEEC), is also a regulated electric utility that distributes electric energy to its customers. Its distribution business consists primarily of the purchase, delivery and sale of electricity to its residential, commercial and industrial customers. Its furnished retail franchise electric service to approximately 1.58 million customers in 159 cities and towns in eastern and western Massachusetts, including Boston, Cape Cod, Martha's Vineyard and the greater Springfield metropolitan area. It owns, operates and maintains a total of 70 megawatts (MW) of solar power facilities on 22 sites in Massachusetts. It sells energy from these facilities into the ISO-NE market, with proceeds credited to customers.