Why does Great Britain curtail wind power?

Great Britain curtails wind power when the transmission network can't carry it to where it's needed, mostly from Scotland to England. NESO pays wind farms behind the bottleneck to reduce output and pays other generators, mostly gas, to replace them. In 2025 this cost £1.47bn. 1

What is wind curtailment?

Wind curtailment is when a wind farm is told to produce less electricity than the wind would allow. In Great Britain it usually happens because of a network constraint: the transmission lines between the wind farm and the people using the electricity are already full.

Curtailment is different from a wind farm standing still because there's no wind, or because it's down for maintenance. A curtailed wind farm could generate, but the system can't use the power where it's produced.

Why does curtailment mostly happen in Scotland?

Most curtailment happens in Scotland because wind capacity there has grown faster than the network that carries power south.2 Scotland has some of Europe's best wind resources but a relatively small population, so much of its wind power has to travel to England.

That power crosses a series of boundaries on the transmission network. The best known is B6, which runs roughly along the border between Scotland and England. Two main transmission corridors cross it, with a secure transfer limit of around 4.5 GW.3 When Scottish wind output is more than local demand and the boundaries can absorb, something has to give.

Planned outages for maintenance and upgrades can reduce boundary capacity further. That's one reason curtailment costs can rise even while new lines are being built.3

How much does curtailment cost?

In 2025, Great Britain spent £1.47bn paying wind farms to switch off and paying gas plants to replace their power, according to Octopus Energy's Wasted Wind tracker.1 By early October 2026, more than £1.5bn had already been spent that year, three months earlier than in 2025.1

Most of that cost isn't the payment to wind farms. Modo Energy estimates that in 2025, payments to Scottish wind farms for curtailment were around £350m, while the replacement generation, mostly gas, cost more than £1bn.2

Figures vary between sources because they measure different things. Some count only wind curtailment and its replacement. Others count all transmission constraint costs: Modo Energy puts those at £1.9bn in the 2024/25 financial year, about 71% of Great Britain's total balancing costs.2 You can follow the latest figures on the Wasted Wind tracker.4

Measures of constraint cost in Great Britain
Measure Period Cost Source
Wind curtailment plus replacement generation 2025 £1.47bn 1
Wind curtailment plus replacement generation 1 January to early October 2026 More than £1.5bn 1
All transmission constraint costs 2024/25 financial year £1.9bn 2

Who pays for curtailment?

Energy bill payers do. NESO recovers the cost of balancing the system, including constraint payments, through Balancing Services Use of System (BSUoS) charges. Since 1 April 2023 these charges have been paid by final demand, through electricity suppliers, rather than by generators.5 Suppliers pass them on to household and business customers.

How is curtailment managed?

Most curtailment is managed through the Balancing Mechanism, the market NESO uses to balance the system one half-hour at a time. Wind farms behind a constraint submit bids, which are prices for reducing their output. When NESO accepts a bid, the wind farm reduces its output and is settled at its bid price. NESO then accepts offers from generators elsewhere to make up the shortfall.

NESO also uses other services, including its Local Constraint Market, which buys extra demand from sites behind the Scottish boundaries when the network is congested.6

Read our guide to Balancing Mechanism bids →

What could reduce curtailment?

There's no single fix. The main options are:

  • More network capacity. New transmission lines and upgrades will raise boundary limits, but large projects take years to build.
  • Storage. Batteries and other storage behind the constraint can absorb surplus power and release it later.
  • Demand turn-up. Sites behind the constraint can use more power when wind is plentiful, so less has to be curtailed. Read our guide to demand turn-up →
  • Better forecasting and bidding. Accurate constraint forecasts help generators, flexible sites and NESO plan ahead and price their responses.

Market design matters too. In July 2025 the government decided to keep a single national wholesale price rather than move to zonal pricing, so constraints will continue to be managed through balancing and flexibility markets.7

Without action, the cost is expected to keep rising. The government has warned it could reach £10bn by 2030.1

How does Nodal Shift help?

Nodal Shift is building software for both sides of the constraint. Nodal Shift Turn-Up will help flexible sites in Scotland get paid to use power that would otherwise be curtailed. Nodal Shift Bid Copilot will help independent generators forecast curtailment and price their bids.