Two international energy companies are proposing a $2 billion project that would carry renewable power from northern and eastern Maine and the Canadian Maritimes to Massachusetts through underground wires along interstate highways. The Northeast Energy Link would primarily serve wind farms to be built in Maine, as well as hydro, wind and other generation sources in Canada. Promoters say the project could lower energy costs by $714 million for Maine customers over 30 years, and generate revenue from lease payments and local taxes. Nova Scotia-based Emera Inc. and its Maine subsidiary, Bangor Hydro-Electric Co., are teaming up with electricity utility National Grid to develop the project. The Portland Press Herald, reports the line will have a capacity of 1,100 megawatts, equal to the output of a large nuclear or gas-fired plant.