About the project
As part of The Great Grid Upgrade, National Grid is proposing to deliver two new substations on a site that is adjacent to our existing Aberthaw Substations. Once operational, the project would replace the two existing Aberthaw substations and be known as Gileston Substation.
What we’re proposing
The way electricity is generated is changing, with more home-grown renewable energy being generated in Britain. The Great Grid Upgrade will enable the electricity grid to carry cleaner, more secure energy from more affordable sources to homes and businesses in every part of Wales and England.
In the Cardiff area, several developers have requested to connect their projects to our network. As a regulated business we have a legal obligation to connect these developments and support the UK’s energy security ambitions.
To connect these projects to our network, National Grid is proposing to develop two new substations. These two new substations would be located on a site adjacent to the existing Aberthaw Substations. Once operational, the project would replace the two existing Aberthaw substations and be known as Gileston Substation.
Substations are a vital link in our network, connecting energy to the grid. They change electricity to the right voltage and direct it safely around the network so power can reach homes and businesses.
The new substations will have an initial capacity of 1.4 Gigawatts (GW), with the potential to rise to 2.1GW to meet future electricity demand. The capacity of the existing Aberthaw substations is 0.4 GW.
The project will also include re-alignment of the existing towers into the new substations.
This would include the removal of three existing overhead line towers to be replaced by four new permanent overhead line towers. We would also need an additional three temporary towers during the construction phase.
Why we’re doing this
This project is part of The Great Grid Upgrade, the largest overhaul of the grid in generations.
Demand for electricity is set to double by 2050 as the way we power our homes, business, industry and transport changes. We need to upgrade the grid now to meet this increase in demand.
The existing transmission network – including the existing Aberthaw substations – was largely built decades ago. It was not designed to transport electricity from where it is increasingly being generated today from offshore wind and solar sources.
In the Cardiff area, several developers have requested to connect their projects to our network. As a regulated business we have a legal obligation to connect these developments and support the UK’s energy security ambitions.
To connect these projects to our network, National Grid is proposing to develop two new substations. These two new substations would be located on a site adjacent to the existing Aberthaw Substations. Once operational, the project would replace the two existing Aberthaw substations and be known as Gileston Substation.
Consent for our project
We will need planning consent for the construction of the two new substations from the Vale of Glamorgan Council.
Prior to submitting our planning application, we want to share details of our plans with the local community and key stakeholders and to receive feedback that will help shape our plans.
Also, before submitting our planning application, we will need to carry out statutory Pre-Application Consultation where a copy of our draft planning application will be made available for public viewing. Site notices, notices to specialist consultees and detail of how to view our draft application will be provided before we carry out our statutory Pre-Application Consultation.
We will be seeking a Section 37 consent for the overhead line works separate to the main planning application. Section 37 consent applications in Wales are determined by the Secretary of State for Energy Security and Net Zero, following consultation with the local planning authority and other statutory consultees.
If the project is consented by Vale of Glamorgan Council, we will seek a separate planning consent from the Council to demolish the two existing substations.
However, in the meantime, our two existing Aberthaw substations will continue to operate safely.
Investing in our communities
Communities are at the heart of the UK’s transition to more secure, cleaner, home-grown energy from more affordable sources.
National Grid has a long-standing commitment to the communities we work alongside, and we want to ensure lasting benefits for the people and places that host our new infrastructure.
If planning approval is granted, NGET working alongside our contractors, will support and invest in the local community in a range of ways including through local grant funding, skills development, schools outreach and volunteering.
We want to hear your views!
We believe it is important to share information about our project with people living and working locally and receive their feedback. The feedback will help us shape our plans as we continue to develop our proposals. We aim to minimise the impact of our project on the local community as far as we can.
We are inviting you to an in-person drop-in event on 6 October 2026 where you can view our plans at this early stage, talk to members of our project team and provide feedback.
Alternatively, you can attend our online webinar on 8 October 2026 where our project team will talk through the plans and answer your questions.
Drop in event 2.30pm to 7pm Tuesday 6 October 2026 The Gathering Place, Flemingston Road, St Athan, Vale of Glamorgan, CF62 4JH No booking is required | Online webinar 6.30pm to 7pm Thursday 8 October 2026 Please sign up by emailing [email protected] |
If you can’t attend our drop in event or webinar you can provide feedback using our online feedback form. You can also contact us by using the following details.
Complete the feedback form online: re-url.uk/WG7N
Email: [email protected]
Phone: 01446 501291
Write: Freepost ABERTHAW SUBSTATIONS (no further address or stamp required)
Please submit your feedback by Monday 19 October.
Next steps and project timeline
The project timeline below outlines the key milestones for the Aberthaw Substations Redevelopment project.
May 2025 - Survey work
We informed local landowners and councillors that we were starting survey works on site and in the local area. The project team undertook technical assessments and started shaping the plans for the project.
October 2026 - Informal engagement
Inviting the local community and stakeholders to a drop in event and an online webinar to learn about our plans for the Aberthaw Substations Redevelopment.
The feedback received at this stage will help us shape our plans as we continue to develop our proposals.
You can find out more details on the ‘About the Project’ page.
November 2026 - Launching Statutory Pre-Application Consultation (PAC)
Before we can submit our planning application to the Vale of Glamorgan Council we will need to undertake statutory Pre-Application Consultation (PAC).
In November we intend to launch the PAC which will last for 28 days. During the PAC you will be able to view all of our draft application documents in the ‘Document Library’ tab and will be able to provide feedback through this website.
We will publicise this consultation to bring it to the attention of the local community, adjoining owners and occupiers, community consultees and specialist consultees.
December 2026 - PAC closes
After the end of the 28-day PAC period, the project team will review the feedback from our consultation and seek to finalise all project documents in preparation for submitting a Town and Country Planning Act (TCPA) application to the Vale of Glamorgan Council.
Early 2027 - Application submitted
We will submit our planning application to Vale of Glamorgan Council.
2028 onwards
Subject to approval, we will work closely with partners to deliver the project.
The Great Grid Upgrade is the largest overhaul of the grid in generations and will future proof the grid for years to come, facilitating the transition to a cleaner and more affordable energy future. It will enable us to carry more clean, secure energy from where it is generated to where it is needed, boosting energy security and helping the nation become more self-sufficient.
Find out more about The Great Grid Upgrade.
National Grid is an energy company operating in the UK and US. Our business plays a vital role in connecting millions of people to the energy they use every day, while continually seeking ways to building a secure, cleaner and more affordable energy system for the future.
Demand for more secure, cleaner, home-grown energy from more affordable sources is accelerating. It’s a big challenge that requires a big response. We are investing £31 billion in our electricity transmission network over the next five years to adapt and develop our network of pylons, overhead lines, cables and substations ensure we can meet increasing demand for electricity and connect new sources of low carbon energy to homes and businesses.
Follow this link to learn more about our business areas - https://www.nationalgrid.com/about-us
National Grid Electricity Transmission (NGET) sits at the heart of Britain’s energy system, connecting millions of people and businesses to the energy they use every day. We own, maintain and develop the high voltage electricity transmission network in England and Wales. We safely carry power from where it is generated to where it can be distributed to homes and businesses via lower voltage regional networks.
NGET is proposing to deliver two new replacement substations on a site adjacent to our existing Aberthaw substations.
The new substations will continue being a point of connection for green energy generation and have a planned initial capacity of 1.4 GW, with the potential to rise to 2.1 GW. The current capacity of the existing substations is 0.4 GW.
This upgrade of critical infrastructure will allow us to continue feeding energy to the Cardiff area to meet the increasing demand.
The substations will be situated in two new buildings.
One substation will connect to the 275 kV network and the other to the 132 kV network.
At this stage of the design, the 275 kV substation building is 139m x 29.2m and 14m high, whilst the 132 kV is 73.4m x 20.5m and 13.5m high.
Our intention is to mitigate visual impacts as far as possible using landscaping and screening.
The proposed overhead lines work includes the following:
The removal of three existing overhead line towers which will be replaced by four proposed permanent overhead line towers.
Three temporary towers will also be required during the construction phase.
We will develop a traffic management plan that will set out how we plan to reduce our time on the roads, the routes we take and where we will park.
We will work closely with the local authority and take guidance from them to further reduce our impact – examples included restricting our vehicle movements to certain times of the day to avoid busy periods.
There is the potential of some noise during construction, but our contractors will regularly monitor noise to ensure it stays within the levels permitted under local environmental health requirements. We will produce a construction noise assessment as part of our planning application.
We will only demolish the existing Aberthaw substations after the new substations are completed and fully operational. The demolition works are not part of our planning application and we will be seeking separate permission from Vale of Glamorgan Council.
The new substations will be an upgrade on the existing substations. The capacity of the existing Aberthaw substations is 0.4 GW. The new substations will have a planned initial capacity of 1.4 GW, with the potential to rise to 2.1 GW.
Even though we are demolishing the existing substations, they are still safe and fit for purpose and will continue to operate as they have done until the new substations are completed and operational.
We don’t anticipate any significant noise when the proposed new substation is operational. Typically, substations generate a low frequency ‘hum’, similar to the sound from overhead lines when operational. However, to support our planning application, we will be carrying out acoustic surveys to assess background and operational noise, which will also inform whether we need to consider any mitigation measures, such as landscaping and acoustic fencing, to minimise any potential impacts on nearby residential areas.
We will be producing an operational noise assessment to support our final planning application.
We’ll ensure that any light pollution is kept to minimum during both the construction and operational phase. Substations aren’t generally lit or permanently illuminated, other than sensor-activated security lighting for nighttime access.
We will be producing a lighting assessment as part of our final planning application.
At this stage of the project, the most detailed plans will be presented at our drop in events and online webinar. Following the drop in, we will upload the materials presented in the ‘Document Library’ tab.
When we undertake our statutory Pre-Application Consultation (PAC) all draft application documents, including the most up-to-date plans, will be available in the ‘Document Library’.
You can provide feedback or contact us with queries via the following:
Complete the feedback form online: re-url.uk/WG7N
Email: [email protected]
Phone: 01446 501291
Write: Freepost ABERTHAW SUBSTATIONS (no stamp or further address is required)
The deadline for comments is 19 October 2026.