Green Line is a high voltage direct current (HVDC) electric transmission system that will transfer 800 to 1000 megawatts (MW) of electric energy from Aroostook County, Maine to greater Boston, Massachusetts. The full route is via a combination of a terrestrial transmission line in Maine and submarine cable across the Gulf of Maine to Massachusetts. Converter stations at each end of a +/-320 kV direct current (DC) transmission line converts alternating current (AC), like that used in the typical household, to direct current (DC). DC is the most efficient way to move electricity long distances. HVDC systems provide great flexibility and near instantaneous control over how much and in which direction power flows, thus proving many reliability benefits to the larger electric grid.