More than 12TWh of renewable electricity was curtailed across Great Britain and Ireland in 2025 due to grid constraints, according to a new report from Montel EnAppSys.
The report said 12.3TWh of clean energy was turned off, enough to meet the annual electricity demand of every domestic household in London.
It added that Great Britain accounted for 10.2TWh of the total, marking a 22% rise on 2024 levels.
Generators in Scotland represented over 98% of GB’s curtailed volume at just over 10TWh, with northern Scotland alone curtailing 8.8TWh.
Ireland curtailed 2.1TWh, sufficient to power all homes in County Dublin for a year, while Northern Ireland curtailed 24% of available wind energy.
Report author Fintan Devenney, senior energy market analyst at Montel EnAppSys, said: “The analysis shows that only 61% of the wind power which could have been generated in Northern Scotland actually made it to the grid.”
He added: “Whilst the government’s goal of meeting 95% of annual demand with electricity generated from renewable sources by 2030 is laudable, ensuring the efficient siting and production of power to meet demand will become increasingly important.”
Devenney said: “It’s also worth noting that the amount of electricity curtailed in GB could have powered every data centre in the country in 2025.”
He stated: “A holistic view of policy which will enable the optimal siting of generation, sufficient investment in grid infrastructure and the correct investment signals to help alleviate grid constraints is now crucial and the strategic spatial energy plan will be key to achieving these aims.”