A Meter Point Administration Number, also known as MPAN, Supply Number or S-Number, is a 21-digit reference used in Great Britain to uniquely identify electricity supply points such as individual domestic residences. The gas equivalent is the Meter Point Reference Number. The system was introduced in 1998 in order to provide a competitive environment for the electricity companies, and allows consumers to switch their supplier easily as well as simplifying administration. Although the name suggests that an MPAN refers to a particular meter, an MPAN can have several meters associated with it, or indeed none where it is an unmetered supply. A supply receiving power from the network operator (DNO) has an Import MPAN, while generation and microgeneration projects feeding back into the DNO network are given Export MPANs.