Energy company ENGIE and Canadian investor CDPQ will invest up to £1 billion in refurbishing two major pumped storage hydro plants in the UK. The investment aims to extend the operational life of the Dinorwig and Ffestiniog plants, key assets in the UK’s electricity system.
ENGIE owns 75% of the facilities through First Hydro Company, a joint venture with CDPQ, which holds the remaining 25%. Together, the two sites provide 2.1GW of storage capacity, representing 74% of the UK’s pumped storage hydro and about 5% of its total power generation capacity.
Work has already begun on a 10-year refurbishment project at Dinorwig, following an eight-year overhaul at Ffestiniog. Both sites are located in North Wales and play a central role in balancing the UK’s electricity grid by providing rapid-response backup power during peak demand periods.
Replanting efforts at Dinorwig may include replacing up to all six generating units, although a final investment decision has not yet been made. At Ffestiniog, two units have already been rebuilt, with the remaining two set to be completed by the end of 2025.
The programme includes the replacement of main inlet valves at both sites. These valves, among the largest in the world, were developed using scaled laboratory models and AI technology to improve efficiency. The stations must be fully drained before valve replacement, a process that takes two weeks due to high water pressure and occurs only once every 40 years.
Dinorwig’s replanting will involve complex engineering, custom lifting systems, and on-site tuning of valve seals. The entire upgrade is expected to take up to a decade.
Miya Paolucci, UK CEO of ENGIE, said: “ENGIE is a key player in the UK’s energy transition and we are making significant financial and resource commitments to reach our decision on whether to invest in the full or partial re-planting of Dinorwig.
“Flexible storage is essential for net zero carbon operation of Britain’s electricity system. It helps balance the system by ensuring there’s always a large volume of ‘back up’ power on standby, that can be delivered in very fast timescales if required. We’re very proud to contribute to the electricity security of supply and green energy ambition of the UK with these extraordinary assets.”
Wales’ First Minister, Eluned Morgan, said: “The renewable energy sector is creating exciting economic opportunities for Wales and is vital in ensuring we meet our future energy targets while reducing our reliance on fossil fuels.
“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.”
Ffestiniog, commissioned in 1963, was the UK’s first pumped hydro plant. Dinorwig, opened in 1984, remains Europe’s largest and fastest-acting pumped storage station. Two of Dinorwig’s six main inlet valves were replaced in 2023, with the remaining four scheduled for 2025.
You can find regular updates on the project on the First Hydro Refurbishment Project page.
