Major Investment and Project Timelines

ENGIE’s £1 billion investment programme is already underway and will keep Dinorwig and Ffestiniog in operation for at least another 25 years. These flexible generation assets, based in North Wales, are reaching end of life, and the investment will ensure clean energy continues to flow into the next few decades, helping the UK achieve Clean Power by 2030.

At Ffestiniog, the re-planting will be completed by July 2026, following a 9‑year refurbishment. At Dinorwig, work has only just begun. Due to the scale and complexity of the project, it will take up to 10 years to complete, and a final investment decision on how many units to replant is still to be made. Replanting could involve the complete refurbishment of up to all six generating units, requiring specialist technology, bespoke lifting systems, and expert contractors.

Replanting and Refurbishment Process

Replanting involves replacing generating units and main inlet valves, some of the largest in the world, which control the flow of millions of litres of water. To carry out the work, the plants must be “drained down” – with water stored in the lower reservoirs only. The water pressure in the shafts is higher than a nuclear submarine can withstand, so the drain down happens slowly and carefully over several weeks.

Once empty of water, engineers climb inside the shafts to conduct thorough safety and integrity inspections. Dinorwig, with its 1.8 GW capacity, and Ffestiniog, with 0.3 GW, play a vital role in keeping the national electricity system balanced. They provide instant flexibility at short notice, helping to manage daily consumption patterns and supporting the integration of intermittent renewables.

Energy Security, Jobs, and the Future

Secretary of State for Energy Security and Net Zero, Ed Miliband said: “Companies like ENGIE understand that clean energy is the economic opportunity of the 21st century, and are investing in the technologies the UK needs to support lower energy bills, protect our energy security, and create good local jobs.”

First Minister of Wales, Eluned Morgan said: “Investments such as these create high quality jobs for the local community. ENGIE is a longstanding investor in Wales, employing around 200 permanent staff and I’m pleased to support its replanting scheme, which will see the facilities continue to operate for another 25 years.”

Assets on this scale are incredibly difficult to build today, so we believe it is essential to preserve and cherish the existing clean power assets we have in the UK if we are to achieve the energy transition.