The way we generate electricity in the UK is changing rapidly and we're transitioning to cheaper, cleaner and more secure forms of energy like new offshore windfarms and solar farms.
We need to make changes to the network of overhead lines, pylons, cables and other infrastructure that transports electricity around the country, so that everyone has access to clean electricity from new renewable sources.
National Grid is extending Cellarhead substation to reinforce the network and enable future new connections to facilitate The Great Grid Upgrade, supporting the UK’s drive to net zero. As a regulated business, we have a legal obligation to connect customers to our network when a connection is requested.
Our work at Cellarhead
We are constructing a small extension to the north of the substation on land that National Grid owns, while also carrying out maintenance of existing equipment on site.
To carry out this work safely, we have secured for permission to temporarily close and divert some of the public rights of way that pass near the substation.
Throughout the project we are committed to engaging with the local community and keeping people updated on our progress.
On Wednesday 21 May we held a public drop-in event at Wetley Rocks Village Hall. At this event we presented details about the planned construction work, the temporary closures and diversions to the public rights of way around the site, as well as our Community Grant Programme.
You can download a copy of the information boards we presented at the event here.
Supergrid transformer delivery
On Monday 2 June 2025 National Grid delivered a large supergrid transformer to Cellarhead substation as part of essential upgrades at the site to ensure safe and reliable energy supplies in the region into the future.
This will replace an existing transformer that is reaching the end of its operational life, as part of routine maintenance work – it is not directly related to the plans to expand the substation which were recently presented to members of the public.
Transformers are vital high voltage devices which boost substations’ capacity and resilience, stepping voltage up or down so electricity can be efficiently transmitted from power generators and safely distributed to homes and businesses via regional networks.
What is a substation?
Electrical substations, such as Cellarhead substation, play a key part in transmitting electricity through the network – keeping the lights on in people’s homes.
One of the typical main roles of substations is to convert electricity into different voltages. The voltage is stepped up or down through equipment called transformers, which sit within the substation site.
This means the electricity can be transmitted throughout the country by National Grid and then delivered at a lower voltage to local homes and businesses by the Distribution Network Operator.
Frequently asked questions
NGET owns and maintains the high-voltage electricity transmission network infrastructure in England and Wales, making sure electricity is transported safely and efficiently from where it's produced to where it's needed. We don't generate energy ourselves.
NGET is separate to the National Energy System Operator (NESO). NESO operates the electricity system, balancing supply and demand across transmission infrastructure owned by NGET, Scottish Hydro Electric Transmission Ltd and SP Energy Networks.
This high-voltage electricity is then passed onto one of the fourteen Distribution Network Operators (DNOs) across the country.
As part of our Ofgem licence to operate, NGET must offer a connection to developers wanting to connect new sources of electricity generation to the national transmission system.
While the nature of new infrastructure means it cannot be without impact, our transmission licence requires National Grid to be efficient, coordinated and economical when formulating proposals, whilst also considering the effect on the environment.
Through these plans we'll deliver at least a 10% increase in biodiversity net gain (BNG) on site. We'll also undertake environmental surveys to ensure we are not harming the environment and are providing the best mitigation.
There are several distinct processes that National Grid uses to determine where developers’ projects connect to the national electricity network. The process followed to decide this is dependent on the type of generation, proposed capacity and when the developer applied to connect.
To enable connection requests in the area, which cannot be achieved by existing infrastructure.
As a regulated business, National Grid has a legal obligation to connect customers (such as renewable energy projects) to our network when a connection is requested.
The country’s electricity grid was originally built with the purpose of transmitting electricity created from coal- and gas-fired power stations. But as the UK moves away from fossil fuels and increases clean energy generation, we’ll all be using more electricity than ever before to power our homes, businesses and transport.
This means that we’ll need to build five times more electricity transmission infrastructure by 2030 than we’ve constructed in the last 30 years, as well as making other changes to our grid to help the UK transition to a clean energy future.
Infrastructure projects across England and Wales, like our proposals for Cellarhead, are helping to connect more clean, affordable energy to your homes and businesses.
This extension is not directly part of The Great Grid Upgrade.
However, as the UK moves away from fossil fuels and increases clean energy generation, we’ll all be using more electricity than ever before to power our homes, businesses and transport. Therefore, there will likely be a need for further connections to sites like Cellarhead.
We have a legal obligation to respond to developer requests to connect to our network – whether solar, battery storage, wind power or any other energy generator. There are a number of energy proposals in the local area that may require connections in the future – we'll consider these at the time as appropriate.
Where new connections and a planning application is required, we'll engage with the local community over our plans.
Please note that National Grid does not generate energy and our plans will also be separate from any other infrastructure plans in the area.
Yes.
We're committed to providing a safe and reliable electricity distribution supply, while minimising risk to the public and protecting our planet. National Grid owns more than 300 large substations and we have established policies, processes and cultures to reduce risk and carry out our work safely.
Construction of the extension is expected to be completed in summer 2027. We will work with the community throughout the project to ensure that any disruption is minimised and that residents are kept up to date.
The map above shows how our vehicles will be accessing the site from the road and where the spoil from the programme of earthworks will be transported to. Starting in June 2025, this phase of work will take around four months to complete and is expected to have the most vehicle movements around the substation.
We have installed temporary traffic signage on the approach to the site to provide advanced warning and our contractors will be considerate to other road users at all times.
We have undertaken a noise assessment and will continue to monitor the noise levels as work progresses, which will be kept to a minimum. Once completed, there is not likely to be any impact on light or noise pollution.
We anticipate any visual impact to be minimal as the site is already well screened by existing vegetation and woodland. No additional overhead lines or pylons will be required as part of the project.
The extension will be 125m wide x 25m long, which is a three per cent increase in the substation’s size. The substation’s height will not increase.
Future work at the substation will be determined by the requirements of our customers and we don’t have further details of future development at this stage. We remain committed to keeping local residents and stakeholders updated whilst we fulfil our obligations to connect customers to the network.
Contact us
If you have any queries, please contact our community relations team:
Email: [email protected]
Telephone: 0800 138 5408 (Monday – Friday, 9am to 5:30pm)
Post (using Freepost – no stamp needed): Freepost RTBU-HAYY-LCUX, 7 Bayley Street, London WC1B 3HB
Stay informed
You can also sign up to our mailing list to receive any project announcements as it moves forward.