We own and operate the gas National Transmission System (NTS) in Great Britain, with day-to-day responsibility for balancing supply and demand. Our network comprises approximately* 7,660 kilometres (4,760 miles) of high-pressure pipe and 618 above-ground installations.
* AR 2016/17 figures
The gas industry connects producers, processors, storage, transmission and distribution network operators, as well as suppliers to industrial, commercial and domestic users.
Production and importation
We do not produce gas in the UK. Gas used is mainly sourced from gas fields in the North and Irish seas, piped from Europe and imported as LNG.
There are seven gas reception terminals, three LNG importation terminals and three interconnectors connecting Great Britain via undersea pipes with Ireland, Belgium and the Netherlands. Importers bring LNG from the Middle East, the Americas and other places.
In the UK, we own and operate Grain LNG, an importation terminal and storage facility at the Isle of Grain in Kent, which charges customers under long-term contracts for various services. These include access to our importation terminal, storage facilities and capacity rights.
The transmission systems generally include pipes, compressor stations and storage facilities, including LNG storage. They connect production through terminals to the distribution systems.
In the UK, gas enters the transmission system through importation and reception terminals and interconnectors and may include gas previously held in storage. Compressor stations located along the network play a vital role in keeping large quantities of gas flowing through the system, particularly at times of high demand.
The gas transmission system has to be kept constantly in balance, which is achieved by buying, selling and using stored gas. This means that, under normal circumstances, demand can be met. We are the sole owner and operator of gas transmission infrastructure in Great Britain.
Gas leaves the transmission system and enters the distribution networks at high pressure. It is then transported through a number of reducing pressure tiers until it is finally delivered to consumers.
There are eight regional gas distribution networks in the UK, none of which are owned by us.
Pipeline shippers bring gas from producers to suppliers, who in turn sell it to customers.
We do not supply gas in the UK. However, we own National Grid Metering, which provides meters and metering services to supply companies, under contract.
Customers pay the supplier for the cost of gas and for its transportation. We transport the gas through our network on behalf of shippers, who pay us transportation charges.
Understanding gas storage
The UK still gets more than 40% of its gas from the North Sea, as well as from other sources. gas storage – short, medium and long-term – is part of our diverse range of gas supplies and provides around 10% of our gas over the winter period (October to March).
The following are frequently asked questions about gas storage:
Where does our gas come from?
Across the year we still get 40 to 45%of our gas from the North Sea (or UK Continental Shelf – UKCS – as it’s known in the industry). We also receive shipments of liquefied natural gas (LNG) into three import terminals around the country, as well as Norwegian and continental gas through a series of interconnectors and pipelines.
Some of the gas from these supply sources can be stored for use when it’s needed.
How is gas stored?
There are two different types of gas storage:
- Long range – there is one long-range storage site on the national transmission system: Rough, situated off the Yorkshire coast. Rough is owned by Centrica and mainly puts gas into storage (called ‘injection’) in the summer and takes gas out of storage in the winter.
- Medium range – these commercially operated sites have shorter injection/withdrawal times so can react more quickly to demand, injecting when demand or prices are lower and withdrawing when higher.
How long does storage last?
When the long-term storage at Rough is completely full, it takes more than three months to empty because the gas can only be ‘withdrawn’ at a certain rate.
There are also several medium-range storage (MRS) sites, although it’s difficult to say exactly how long this storage would last because these sites ‘inject’ gas into storage in the winter too, so an MRS site may be delivering gas into the system one morning and (depending on price/conditions) refilling in the afternoon and topping itself up again.
Why does the UK have less gas storage than other European countries?
The strength of the UK gas supply lies in its diversity. The UK market is able to deliver gas to meet the 1 in 20 peak demand. Other European countries rely much more heavily, or totally, on imported gas and don’t have additional capacity and diversity, so have to rely on storage to meet their high-demand periods.
Will we need storage as North Sea gas declines?
The strength of the UK gas supply lies in its diversity and the fact that the UK market is able to deliver gas well in excess of maximum demand. The industry needs to ensure that we have gas to replace UKCS, whether it’s more imported LNG, more interconnector capacity to get gas from the continent, or more storage. As the gas supply market is ultimately responsible for ensuring there is enough gas to meet its customer needs, the market must decide how to replace UKCS.
Storage provision is always under evaluation in the UK. As the system operator, we provide an overview of existing storage sites, those under construction and proposed future developments. You can read about these in our Gas Ten Year Statement.
Should we worry when storage stocks get low?
Storage stocks naturally get lower towards the end of winter and, as system operator, this is what we expect. Storage is an important but relatively small part of the overall supply mix. We receive our gas supplies from many different sources.