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The Great Grid Upgrade: Expanding Britain’s power network
The Great Grid Upgrade is a marketing campaign created by National Grid to explain its construction of 17 new major power transmission lines.
Over the next decade, this will involve 550 kilometres of new overhead power lines, approximately 1,300 steel pylons, and six new subsea high-voltage cables.
Framed as essential for Britain’s net zero transition and energy security, the campaign makes the case for spending tens of billions of pounds on new infrastructure. But behind the marketing lies a simple reality: this is one of the largest power line-building programmes Britain has ever seen.
In this guide, we cut through the marketing to explain the facts about the Great Grid Upgrade.
Here are the key parts of our guide:
- What is the Great Grid Upgrade?
- Why do we need the Great Grid Upgrade?
- Where is the Great Grid Upgrade happening?
- How much does the Great Grid Upgrade cost?
- Environmental and local opposition to the Great Grid Upgrade
What is the Great Grid Upgrade?
The Great Grid Upgrade is National Grid’s programme to modernise and expand Britain’s high-voltage electricity network.
It comprises 17 major infrastructure projects that will extend the high-voltage power grid through the construction of new overhead lines, pylons, substations and subsea cables.
Why do we need the Great Grid Upgrade?
The Great Grid Upgrade is necessary to accommodate major changes in the way power is generated in Britain.
As part of the government’s Clean Power 2030 strategy, the grid is reducing its reliance on fossil fuels by incorporating the following increases in capacity from low carbon energy sources:
- Offshore wind: Quadrupling the power output of offshore wind farms. Much of the new capacity will come from projects already under construction, such as the Dogger Bank wind farms in the North Sea.
- Onshore wind: Doubling onshore wind capacity, with most of this located in North Wales or Scotland, far from the main demand centres in England.
- Nuclear power: Integrating the substantial output from the Hinkley Point C and Sizewell C nuclear power plants currently under construction.
- Energy storage: A fivefold increase in the capacity of storage facilities connected to National Grid, providing balancing services to manage intermittent generation from wind farms.
The existing high-voltage transmission network is not capable of reliably carrying the additional power from these new generators. The Great Grid Upgrade will remove bottlenecks and enable clean energy to flow to the main demand centres in the Midlands, the South of England and London.
Where is the Great Grid Upgrade happening?
There are 17 major elements of the Great Grid Upgrade, involving the installation of entirely new transmission routes. These include a mixture of subsea and onshore lines.
The map below shows the proposed route of each project.
Source: National Grid – Great Grid Upgrade project background document
Below, we have summarised the details of each project, listed from north to south.
Eastern Green Links 1-5
Five separate subsea routes will connect Scotland to England, laid under the North Sea along Britain’s east coast. These links are planned to carry 500 kV direct-current electricity.
Where the cables make landfall, they will be buried underground and terminate at newly constructed converter stations, which will connect to the existing grid.
The connections are designed to efficiently transmit intermittent power from Scotland into England to help minimise curtailment of Scottish wind farms.
National Grid plans five separate routes to provide system resilience and to allow delivery in phases.
Yorkshire Green
Location: York, Yorkshire
New overhead lines: 10 km of new overhead lines with 33 pylons, north-west of the city of York, near the villages of Upper Poppleton and Wigginton.
New substations: Construction of substations at Overton and Monk Fryston.
Reason: To relieve congestion on the existing Yorkshire network and improve north–south transmission pathways from Scotland.
Pentir to Trawsfynydd
Location: North Wales
New overhead lines: N/A – underground cabling only, as the route passes through Snowdonia National Park.
New substations: Construction of a new substation south of Brîncr.
Reason: North Wales has abundant wind resources in its mountainous areas. Reinforcement of the grid is necessary for North Wales to become a net exporter of electricity to the rest of the country.
North Humber to High Marnham
Location: Yorkshire and Nottinghamshire
New overhead lines: 90 km of new high-voltage overhead lines between Birkhill Wood and High Marnham.
New substations: Two new substations at either end of the line, at Birkhill Wood, near Hull, and at High Marnham, near Lincoln.
Reason: To improve north–south transmission capacity to accommodate power from a number of planned offshore wind farms on the east coast.
Brinsworth to High Marnham
Location: South Yorkshire, Derbyshire and Nottinghamshire
New overhead lines: No new overhead lines, only upgrades to existing infrastructure.
New substations: Three new substations at Brinsworth in Rotherham, Chesterfield and High Marnham.
Reason: To improve the transmission of power from the north of England to homes and businesses in the Midlands.
Chesterfield to Willington
Location: Derbyshire
New overhead lines: 60 km of overhead lines between Chesterfield and Willington.
New substations: A new substation in Chesterfield.
Reason: To improve electricity transmission capacity, enabling clean energy from the north of England to be transported into the Midlands.
Weston Marsh to East Leicestershire
Location: Cheshire and the East Midlands
New overhead lines: 60 km of overhead lines from Weston Marsh, near Runcorn, to Melton Mowbray.
New substations: Two new substations on the route, at Corby Glen and Wartnaby.
Reason: To strengthen the transmission route for new renewable capacity entering the East Midlands.
Grimsby to Walpole
Location: Lincolnshire and Norfolk
New overhead lines: A new 140 km overhead line running north–south between Grimsby in Lincolnshire and the Fens in Norfolk.
New substations: Five new substations on the route, at or near Grimsby, Walpole, Spalding, and two near Mablethorpe.
Reason: To improve transmission capacity in the area and support the additional power being received from the Eastern Green Links.
Bramford to Twinstead
Location: Suffolk and Essex
New overhead lines: 18 km of new overhead lines running east from near Ipswich to near Great Cornard.
New substations: A new substation at Butler’s Wood.
Reason: To remove a transmission bottleneck in the existing network, enabling greater transfer of power from the east of England.
Norwich to Tilbury
Location: Norfolk, Suffolk and Essex
New overhead lines: 180 km of new overhead lines running south from Norwich to Tilbury on the Thames Estuary.
New substations: Two new substations, one in north Essex and one in Tilbury.
Reason: To add capacity for distributing power from offshore wind farms under construction on the east coast, as well as from a new interconnector with Germany.
Grain to Tilbury
Location: Essex and Kent
New overhead lines: N/A, development of a new tunnel under the Thames Estuary.
New substations: N/A
Reason: The existing tunnel has reached the end of its operational life.
Sealink
A 90-mile subsea electricity cable between Kent and Suffolk. The route will connect Thorpeness and Aldeburgh in Suffolk to Sandwich in Kent.
The installation of Sealink will require new substations in Ramsgate and Saxmundham.
Sealink will enable energy from the under-construction Sizewell C nuclear power station to be transmitted into Kent.
How will the Great Grid Upgrade work?
The Great Grid Upgrade is an umbrella term covering the 17 individual projects described above, which extend the power transmission grid.
This section explains the general process and milestones involved in each of these major development projects.
Milestones for Great Grid Upgrade developments
Here are the typical milestones for each individual Great Grid Upgrade project:
- Identifying the need: The grid operator models future power demand and generation to anticipate bottlenecks in the network.
- Early design and route planning: National Grid proposes a new transmission route to alleviate the expected bottleneck, balancing engineering feasibility, environmental constraints and cost.
- Public consultation and engagement: Communities along the proposed route are invited to comment on the construction plans. Feedback may lead to adjustments in the design.
- Planning and consent: Great Grid Upgrade projects are classified as Nationally Significant Infrastructure Projects, requiring a Development Consent Order under planning regulations. National Grid submits applications to the Planning Inspectorate.
- Ofgem approval: Ofgem, the energy regulator, approves the costs and funding of the project. This sets how much National Grid can spend and how costs will be recovered from consumer bills.
- Construction begins: Physical construction proceeds once National Grid has procured the necessary pylons, cables, transformers, etc. Building a new transmission line typically takes three to six years.
- Testing and commissioning: New lines and substations are tested for safety, stability and integration with the existing grid. Once completed, they are handed over to the grid operator.
Timeline for the Great Grid Upgrade
The individual projects within the Great Grid Upgrade are managed separately and will progress according to the constraints of the planning and consent process.
Under current plans, most of the new subsea and overhead transmission lines will be built between 2026 and 2032.
To view the status of individual developments, visit the project pages on National Grid’s website.
How much does the Great Grid Upgrade cost?
The proposed cost of the Great Grid Upgrade is £19 billion. The majority of this was approved by Ofgem, the regulator, in 2023, but the remainder is subject to approval as part of a five-yearly budget review process.
Ofgem is due to decide on the National Grid’s investment proposal for the next five years in early 2026.
How the Great Grid Upgrade will impact bills
National Grid is a private company that will fund the Great Grid Upgrade. As part of the investment approval process, Ofgem allows National Grid to recover its investment and operating costs through TNUoS charges, which are paid by participants in the wholesale electricity market.
In 2025/26, total TNUoS charges amount to £6.2 billion, accounting for around 10% of domestic and business electricity prices.
According to a TNUoS forecast report from NESO, the grid operator, these charges are expected to rise to £13.6 billion by 2031. Increases in TNUoS charges will affect domestic and business energy suppliers, who are likely to pass on these additional costs to their customers through higher tariffs.
Economic returns from the Great Grid Upgrade
Although the electricity transmission element of bills will rise due to the Great Grid Upgrade, there is a strong argument that overall bills will fall because of a reduction in constraint costs.
Constraint costs occur on windy days when the power produced by UK wind farms exceeds the ability of the National Grid to distribute it.
In such cases, the grid operator instructs wind farm operators to disconnect from the grid, and NESO must compensate them for lost revenue.
In 2024/25, total constraint costs rose to £1.8 billion, which are charged to consumers in the form of BSUoS charges.
The Great Grid Upgrade will increase the grid’s capacity to handle intermittent power generation from renewables, thereby reducing constraint costs for consumers. National Grid estimates that the upgrade will help to avoid £12 billion in constraint costs over a five-year period.
National Grid argues that the Great Grid Upgrade will deliver cheaper domestic and business energy deals over the long term by reducing these constraint costs.
The economic impact of the Great Grid Upgrade
A key reason for grouping and branding the construction of new transmission lines as the Great Grid Upgrade is to highlight its major economic impact.
In addition to lowering overall electricity bills by reducing constraint costs, the programme is expected to support tens of thousands of jobs across construction, engineering, and manufacturing.
Each project in the Great Grid Upgrade is a multi-year endeavour, bringing economic development to coastal and rural communities where these transmission lines are being built.
Environmental and local opposition to the Great Grid Upgrade
Several environmental concerns have been raised regarding the planned expansion of the transmission network under the Great Grid Upgrade. Local campaign groups in affected communities are seeking to block or amend proposed construction work.
In this section, we summarise the three main concerns raised in relation to the Great Grid Upgrade.
Pylon opposition by local groups
Seven of the Great Grid Upgrade projects involve constructing high-voltage overhead cables.
These cables are carried on 50-metre steel pylons, spaced every 300 to 400 metres along the route.
Campaign groups from affected communities argue that these structures will scar the landscape and harm local tourism.
Countryside disruption
The economies of rural communities crossed by the proposed new overhead transmission lines are dominated by agriculture.
Farming groups in these areas have raised concerns about the loss of productive land, difficulties in accessing fields, and restrictions on future land use.
Conservation groups have also argued that the removal of hedgerows to construct new pylons will have a negative impact on biodiversity in these communities.
Disrupted marine protected areas
The Eastern Green Links and Sealink elements of the Great Grid Upgrade rely on high-voltage cables that pass through, or are close to, marine protected areas. These areas exist to safeguard sensitive habitats such as reefs, sandbanks and nursery grounds.
Environmental groups have raised concerns that laying and burying high-voltage cables on the seabed can cause physical disturbance (through dredging and trenching), increase sediment plumes, and generate localised electromagnetic fields that may affect marine life.
The community benefits from the Great Grid Upgrade
National Grid argues that, on balance, the Great Grid Upgrade will be a net positive for the environment, as it will enable the decarbonisation of the grid.
However, there is recognition that the construction of new transmission lines and substations incurs local environmental costs for the affected communities.
To mitigate these costs, a number of schemes and initiatives are being provided by both the central government and the National Grid:
Discount to electricity bills
The government has pledged to provide households living within 500 metres of a newly constructed electricity pylon with a £250 annual discount on their bills for a ten-year period.
Notably, local businesses are not eligible for this discount. Instead, visit our business electricity comparison service to help you find the cheapest tariffs available in your area.
Statutory landowner compensation
Farmers and landowners whose land is crossed by pylons or underground cables are entitled to statutory compensation for the loss of land use, crop disturbance, and access restrictions.
Payments are negotiated on a case-by-case basis, but they are legal entitlements rather than voluntary benefits.
Community grant programme
National Grid operates a grant programme for communities impacted by grid construction or operational activities.
Under the programme, charities, social enterprises and other non-profits can apply for grants of up to £10,000 if they are in areas affected by National Grid’s operations.
What is the strategic importance of the Great Grid Upgrade to the UK
Aside from the direct need to add transmission capacity to the grid, there are several wider strategic reasons why the Great Grid Upgrade is an important project for the UK as a whole.
Delivering Net Zero
Decarbonising the National Grid is a first and necessary step in the UK’s journey towards its legally binding target of net zero emissions by 2050.
Delivering carbon-neutral power by incorporating greater renewable and nuclear power capacity is a critical step towards the decarbonisation of heating (through heat pumps) and transport (through electric vehicles).
Energy security
The UK is currently heavily dependent on importing natural gas through LNG terminals and the Langeled pipeline.
The Great Grid Upgrade will enable fuller use of renewables and reduce reliance on gas-fired power stations for electricity generation. In the longer term, the power network is expected to rely primarily on wind power, a resource the UK has in abundance.
Encouraging private investment
Most of the national transmission grid was built in the 1960s. The modernisation delivered by the Great Grid Upgrade is essential for attracting further investment in wind farms, battery storage and green hydrogen production.
This effort is also supported by Great British Energy, the state-owned investment company seeking to bolster UK supply chains related to large-scale renewables.
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