National Grid Gas (NGG) is the Transmission Owner (TO) and System Operator (SO) of the GB national transmission system (NTS). Under its TO role it is obliged to ensure that adequate NTS capacity is available to support NTS customers gas flow requirements.
To manage this process NGG makes available NTS entry capacity and NTS exit capacity, which NTS gas shippers are obliged to book in order to have the right to flow gas to and from the system on behalf of customers.
Entry capacity provides the daily right to flow gas into the system up to an agreed flow rate. Exit capacity provides the right to offtake gas from the NTS up to a deemed flow rate.
Entry capacity is made available in quarterly, monthly or daily strips via a suite of long and short term reserve price auctions. Exit capacity is made available in annual, and daily quantities, principally via an annual application window, although short term capacity rights can be acquired when capacity is available at the day ahead and within day stage.