Gas is delivered to nine reception points, or terminals, by gas producers.
The gas producers deliver gas to the terminals from offshore facilities at fields beneath the sea around the British Isles and through pipelines which connect to the UK from Norway, Holland and Belgium. In addition, recently commissioned terminals at the Isle of Grain and Milford Haven allow liquefied natural gas (LNG) to be delivered to the terminal by boat from producers all over the world.
After treatment, which includes checking the gas quality meets statutory safety requirements and measuring the calorific value (the amount of energy contained), the gas is transported around Great Britain through over 278,000 kilometres of iron, steel and polyethylene mains pipeline.
From the terminals, gas enters the national transmission system (NTS), which is the high-pressure part of National Grid's pipeline network, consisting of more than 7,600 kilometres of top quality welded steel pipeline operating at pressures of up to 85 bar (85 times normal atmospheric pressure, over 1250 psi). The gas is pushed through the system using 23 strategically placed compressor stations.
The NTS can supply gas to other countries via interconnecting pipelines to Belgium and Ireland.
The NTS supplies gas to UK end consumers from over 175 off-take points including large end users which are primarily large industrial consumers and power stations, who receive gas directly from the national transmission system rather than through a distribution network, and the twelve local distribution zones (LDZ) that contain pipes operating at lower pressure which eventually supply the smaller end consumers, including domestic customers.