In short
Much of Great Britain's new generation, especially offshore wind and Scottish onshore wind, is far from the cities and industry that use the power. The transmission network that carries power from north to south and from sea to shore is already congested, which costs consumers through constraint payments. The answer is a large programme of new overhead lines, underground and subsea cables, HVDC links and substations, planned by NESO, built by the transmission owners and funded through Ofgem's price controls.
Who builds what
- National Grid Electricity Transmission owns the network in England and Wales, and runs its build programme as the Great Grid Upgrade.
- SP Transmission owns the network in central and southern Scotland.
- SSEN Transmission owns the network in the north of Scotland, including the links to the islands.
- Offshore transmission owners (OFTOs) own the cables connecting offshore wind farms. The wind farm developer usually builds the link, then sells it to an OFTO chosen by Ofgem through a competitive tender.
- NESO plans what is needed. Ofgem approves the funding.
Why so much is needed
Three things drive the build:
- Offshore wind. Government targets need many gigawatts of new offshore wind, much of it off Scotland and the east coast of England, connected to shore and carried inland.
- North–south flows. Scotland often generates far more than it uses. When the boundaries between Scotland and England are full, wind farms are paid to turn off and gas plants further south are paid to turn on.
- Demand growth. Electrified heat, transport, industry and data centres are expected to push demand up substantially by the 2040s.
The Electricity Networks Commissioner's 2023 report found that new transmission took around 12 to 14 years to deliver, and recommended halving that. Many of the government's later changes to planning and funding follow from that report.
How projects are planned
Network planning used to be largely piecemeal, with each project assessed as connections were requested. That has changed:
- The Holistic Network Design (2022) set out a coordinated plan for connecting 2030 offshore wind targets, rather than a separate radial link for each wind farm.
- NESO's Centralised Strategic Network Plan will set out the transmission needed over the longer term.
- It will be based on the Strategic Spatial Energy Plan, which sets out where generation and storage should go. See Clean Power 2030 and strategic planning.
How projects are funded
Transmission owners recover their costs through RIIO price controls and TNUoS charges. Because the normal five-year cycle was too slow for projects needed by 2030, Ofgem set up the Accelerated Strategic Transmission Investment (ASTI) framework in 2022. It approved around two dozen large projects for early funding and removed a stage of needs assessment, in return for delivery incentives and penalties for delay. RIIO-T3, which started in April 2026, includes large allowances for further build.
Some new projects may be delivered through competition, with Ofgem tendering the right to build and own them, rather than automatically going to the incumbent owner.
Major projects
Projects underway or in development include:
- Eastern Green Links: subsea HVDC cables along the east coast connecting Scotland and England, including EGL1 from East Lothian to County Durham and EGL2 from Aberdeenshire to North Yorkshire, each around 2GW, with further links planned.
- Onshore reinforcements in England, such as new lines in East Anglia and Lincolnshire to carry offshore wind inland.
- Upgrades in the north of Scotland, including new and upgraded lines and substations, and HVDC links to the Western Isles, Orkney and Shetland.
- Interconnectors to other countries, built under Ofgem's cap and floor regime.
See the big projects tracker for the latest reported milestone on each.
Planning consent
In England and Wales, most large transmission projects are Nationally Significant Infrastructure Projects. They need a Development Consent Order, decided by the Secretary of State after examination by the Planning Inspectorate. In Scotland, overhead lines need consent from Scottish Ministers under section 37 of the Electricity Act 1989, with substations generally going through local planning.
New overhead lines often meet local opposition, with campaigners pressing for underground or offshore routes. These cost several times more and bring their own impacts. Government has introduced community benefit guidance and, for people living near new lines, proposed bill discounts. It has also changed planning law to speed up decisions and limit repeat legal challenges. Follow planning for lines and substations.
Supply chain and constraints
Even with consent and funding, delivery depends on scarce equipment, such as HVDC converters, subsea cable and large transformers, and on skilled workers. Network companies are signing long-term supply agreements and framework contracts to secure capacity. Until new lines are built, constraint costs are likely to stay high.
Sources
Based on material from NESO, Ofgem, the transmission owners and the Department for Energy Security and Net Zero. Project dates change: check the developer's project page for the current position.
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Latest stories on Offshore Wind & Transmission Build, Planning for Lines & Substations, Strategic & Regional Planning. For terms, see the glossary; for key dates, the policy timeline.