The Great Grid Upgrade, led by National Grid, is now moving forward to address these issues. This is the biggest change to Britain’s electricity grid in generations, and it aims to move clean energy more efficiently across the country.

Why Britain Is Facing Grid Constraints

Britain’s high-voltage transmission network was built to transport electricity from large, centralised fossil fuel power stations to urban areas. While this system was effective, many of the original power stations have been decommissioned and much of the UK's renewable energy originates from locations with optimal wind and solar resources, mainly offshore and in Wales, Scotland and the North of England. Meanwhile, electricity demand is rising rapidly. It is expected to grow by 50% by 2035 and double by 2050 due to the electrification of heating, transportation, housing, and industry.

Unfortunately, there is a cost to this relatively new mismatch in generation. In 2025, congested transmission networks prevented clean electricity from reaching consumers, leading to over £1 billion worth of curtailed wind generation because the grid could not transport it through major transmission boundaries across the country. Developers are also facing significant delays; some regions will not have available transmission connection dates until after 2033, leaving projects ready for construction stuck in limbo. This affects both rural energy projects and significant urban developments.

A 2024 industry survey conducted by Cornwall Insight and law firm Weightmans highlights how widespread the issue is: 75% of energy experts view grid connection delays as the main barrier to renewable energy deployment in the UK. 

What Is the Great Grid Upgrade?

The Great Grid Upgrade is National Grid’s initiative to modernise and expand the transmission network. It includes several major infrastructure projects such as new pylons, overhead lines, substations, and subsea cables. National Grid describes it as “the largest overhaul of the electricity grid in generations”. Key elements include:

• Major subsea links transporting Scottish wind power to demand centres in England, bypassing one of the major constraint boundaries (known as B6) on the England/Scotland border.
• New and reinforced onshore transmission routes to ease pressure on crowded corridors serving both urban and rural areas.
• Integration of significant new renewable and nuclear generation, including Sizewell C and the expansion of offshore wind capacity.
• Advances in high-voltage direct current infrastructure, backed by a £59 billion supply chain framework, making the system robust and future-ready.

Overall, the upgrade represents around £19 billion of investment in the grid through to 2030, which constitutes around two-thirds of National Grid’s planned network expansion budget. 

How Will It Help Communities Across Britain?

Unlocking renewable generation

Areas that produce clean energy, whether rural wind farms, coastal offshore wind, or urban and rural solar, will benefit from increased capacity to export power efficiently. Enhanced transmission routes will decrease curtailment and enable the full use of low-carbon electricity.

Supporting nationwide electrification

As homes, businesses, and transportation systems throughout Britain become more reliant on electricity, demand continues to rise. Strengthening the transmission network is vital to support these changes and prevent bottlenecks as the country shifts to low-carbon heating and mobility.

Improving energy security

Upgraded infrastructure helps to ensure that electricity can flow wherever it is needed, regardless of location. This reduces the risk of regional constraints and global events and policy affecting consumers’ supply.

Boosting investment in every region

Better grid access supports investment in solar arrays, battery storage, industrial sites, and commercial developments, benefiting towns, cities, and rural communities. Faster, fairer access to the grid also helps restore investor confidence.

Overhead Lines vs Underground or Undersea Cables

Through our involvement in the facilitation of aspects of the Great Grid Upgrade, one of the questions we hear regularly is: ‘why can’t these new lines be put underground?’.

While this might seem appealing, especially in sensitive landscapes, current research indicates that overhead lines are the most practical and cost-effective choice for grid expansion. An independent study by the Institution of Engineering and Technology (IET) and Mott MacDonald determined that underground cables cost, on average, 4.5 times more than overhead systems, with subsea cables costing up to 11 times more.

These costs would delay the UK’s grid expansion and increase pressure on consumers. There are also practical challenges. Finding and fixing underground faults is more difficult, often requiring excavation that extends outages and disrupts farming activities. Upgrading buried cables is also more complex than extending or upgrading overhead lines, which can be directly accessed and modified as demand increases. Government research supports this view and, while undergrounding is sometimes used (such as in National Parks), it is considerably more expensive and complicated, making it an impractical default option.

The Route Forward

Many aspects of the upgrade are still undergoing planning and consultations. Issues like landscape impact, environmental protection, and land access require careful management.

Despite the challenges, the upgrade offers a rare opportunity to create a more resilient and efficient electricity system.

Further information

Contact Max Johnson