More than 5 terawatt hours (TWh) of renewable electricity were curtailed across Great Britain and Ireland in the first half of 2025 due to grid constraints, according to a report published by Montel Analytics. The figure is equivalent to the energy needed to power every household in Scotland for six months.
The report, Curtailed Renewables in GB and Ireland, highlights growing challenges in integrating renewable energy into the existing grid infrastructure. In Great Britain alone, 4.6 TWh of clean energy was curtailed between January and June 2025 — a 15% increase compared with the same period last year. Generators received £152 million in compensation for the lost output, a cost ultimately passed on to consumers.
“Only 63% of wind power that could have been generated in GB reached the grid,” said Fintan Devenney, senior analyst at Montel and author of the report. “The cost of turning down that other 37% is passed on to energy bills, meaning consumers are the ones left counting the costs.”
Northern Scotland accounted for over 86% of the curtailed electricity in Britain, with 4 TWh of wind energy turned down, costing more than £116 million. The report points to network limitations as a key factor behind the high curtailment figures, particularly in the region.
In Ireland, 905 gigawatt hours (GWh) of renewable electricity were curtailed in the first half of the year, enough to supply all homes in County Dublin for six months. No compensation was paid to generators under current market arrangements, though the report notes that changes to balancing payment rules are expected.
Despite higher volumes of curtailed electricity, the total cost of curtailment in Britain fell by 7% compared to the previous year, attributed to lower average prices per megawatt hour. Phil Hewitt, director at Montel Analytics, said this was largely due to more offshore wind farms backed by Contracts for Difference (CfD) coming online.
“Over time, curtailment costs could become cheaper as windfarms supported by the Renewables Obligation scheme fade away and CfD supported generation continues to build out further,” Hewitt said.
The report also pointed to a significant rise in solar curtailment in Ireland, with 24 GWh curtailed in June 2025—nearly seven times the level seen in June 2024.
Looking ahead, the National Energy System Operator’s (NESO) Future Energy Scenarios project up to 15 TWh of solar curtailment annually by 2050. Devenney urged policymakers and industry leaders to take coordinated action.
“Now is the time for government to come together with industry and build the 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,” he said.
The findings underscore ongoing tensions between rapid renewable deployment and the pace of grid development in the transition to a net-zero energy system.
