National Grid plc is a British multinational electricity and gas utility company headquartered in London, England. Its principal activities are in Great Britain, where it owns and operates electricity and natural gas transmission networks, and in the Northeastern United States, where as well as operating transmission networks, the company produces and supplies electricity and gas, providing both to customers in New York and Massachusetts. National Grid plc is one of the largest investor-owned utility companies in the world; it has a primary listing on the London Stock Exchange where it is a constituent of the FTSE 100 Index, and a secondary listing in the form of its American depositary receipts on the New York Stock Exchange. Wikipedia