NSTAR Electric Company, a regulated electric utility company, engages in the purchase, transmission, delivery, and sale of electricity to residential, commercial, and industrial customers in Massachusetts. As of December 31, 2017, it served approximately 1.4 million customers in Boston, as well as 139 cities and towns in Eastern and Western Massachusetts, including Cape Cod, Martha's Vineyard, and the greater Springfield metropolitan area covering an area of approximately 3,200 square miles. The company is based in Boston, Massachusetts. NSTAR Electric Company is a subsidiary of Eversource Energy.