In a “one of its kind “ report from Montel EnAppSys, the energy analysists reveal that a record 12.3TWh of renewable energy was curtailed last year due to limitations and bottlenecks on the transmission network – most notably in North Scotland.
Indeed, 98% of the curtailed energy was due to turning down wind turbines in Scotland. There was more than 10TWh curtailed across Great Britain alone, which was a 22% increase on the amount wasted over 2024.
Ireland curtailed 2.1TWh – enough to power all homes in County Dublin for the year – while solar energy wastage in the Republic of Ireland was more than four times higher than in 2024.
Despite the increase in wasted clean energy, the total cost of curtailment payments reached £363m, which represents a 10% decrease year-on-year.
The findings uncover a “growing disconnect between renewable generation and grid infrastructure capacity, something which has the potential to raise costs on consumer bills for years to come”, according to the researchers.
“The analysis shows that only 61% of the wind power which could have been generated in Northern Scotland actually made it to the grid,” said report author Fintan Devenney.
“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.
“This is brought into sharper focus by the expected increase in electricity demand from new data centres wishing to connect to the grid as soon as possible, as well as the continued electrification of heating, transport and other sectors."
Much of last year’s curtailed energy was located in areas of weaker grid infrastructure, as physical constraints on the transmission system mean that, no matter how much power is produced in a given area, only a certain amount can flow through the network and make it to consumers at any one time.
The report also shows that the energy demand of every data centre in Great Britain could have been met by last year’s curtailed volume.
To meet the net zero targets set out by the governments of the UK and Republic of Ireland, the researchers said that “greater amounts of renewable generation are required to come onstream than ever before”.
Assessing the potential impacts of new renewables connecting to the grid, Devenney added: “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.”
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Chris Seekings is the Deputy Editor of ISEP’s Transform magazine, which is published biomonthly for ISEP members. Chris’s role involves writing sustainability-related news, features and interviews, as well as helping to plan and manage the magazine’s other day-to-day activities.
