National Grid PLC is an energy transmission and distribution company. The Company operates through three segments: UK Electricity Transmission, UK Gas Transmission and US Regulated. The UK Electricity Transmission segment includes the high-voltage electricity transmission networks in England and Wales and Great Britain system operator. This segment also includes the independent Electricity System Operator (ESO). The UK Gas Transmission segment includes the high-pressure gas transmission networks in Great Britain and system operator in Great Britain. The US Regulated segment includes gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New York and New England and electricity generation facilities in New York. The Company's transmission and distribution services include provision of electricity transmission and distribution services to customers and operation of electricity transmission facilities.