National Grid needs to reinforce and refurbish parts of the existing high voltage power network in North Wales. This work is part of The Great Grid Upgrade- the largest overhaul of the grid in generations.

Enabling a clean energy future for Wales

National Grid needs to reinforce and refurbish parts of the high voltage power network in North Wales.

The way electricity is generated in the UK is changing rapidly to more secure, cleaner, home-grown energy from more affordable sources.

It is predicted that demand for electricity will at least double by 2050 as we shift to clean energy to heat our homes, drive electric vehicles and power our industry.

The Welsh Government wants to meet the equivalent of 70 per cent of Wales’s electricity demand from renewable energy sources by 2030. 

The existing transmission system was largely built in the 1960s and was designed to connect electricity mainly generated in coal-fired power stations to homes in Wales and England.

To allow new sources of renewable energy to be connected to the network, we need to reinforce and refurbish the existing electricity network between Pentir and Trawsfynydd. This will help to keep the network secure by enabling more clean energy to be delivered to homes and businesses.

This is a major project, and it is essential that the strengthened connection is in place by 2030.

This is part of The Great Grid Upgrade, the largest overhaul of the electricity grid in generations, comprising 17 major infrastructure projects across Wales and England. Progress towards green electricity is the most effective way to ensure energy affordability, with homegrown renewable power expected to help to lower energy bills in the long term.

You can read more about our work and our latest plans here.

We currently expect construction to start in spring 2026, though this is dependent on us obtaining the permissions, licences and other agreements.
 

Project timeline

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The permissions we will need

We need planning permissions for the different elements of our project from Cyngor Gwynedd and Eryri National Park. Consent will also be required for the work from the Department for Energy Security and Net Zero (DESNZ).

In September 2025, we carried out statutory Pre-Application Consultations for 28 days for the main elements of the project, in line with Welsh Government legislation. These consultations included providing formal notice of the consultation to landowners, adjoining landowners, local councillors, community councils, and specialist consultees.  

We have carefully considered the feedback received during the consultations and have now finalised our plans. We have now submitted the following four planning applications:  

We have applied to Cyngor Gwynedd for permission to build a substation south of Bryncir; install replacement cables beneath the Glaslyn Estuary and complete other related work; and install new cables and other equipment within our existing Pentir Substation.  

You can view these three applications on Cyngor Gwynedd’s online planning portal:  

• Pentir Substation Application
• Bryncir Application
• Glaslyn Cables Application

We have submitted the application for work at Trawsfynydd Substation to Eryri National Park, because the substation is within the national park.  

You can view this application on Eryri National Park’s online portal:  

• Trawsfynydd Application

The Local Planning Authorities will now assess the respective applications and undertake consultation. We currently expect to receive decisions from the authorities in the coming months.  

Separately, we also require consent for aspects of our work from the Secretary of State for Energy Security and Net Zero (DESNZ). This application process will take place later this year, and when we can share more information about the timings of this, we will let everyone know.