What is curtailment - and why do wind farms get paid to stop?

On a windy night, Scotland’s wind farms can generate far more power than Scotland can use - and more than the wires to England can carry. When that happens, the system operator pays wind farms to curtail: to deliberately produce less than they could. The same night, a gas plant south of the bottleneck may be paid to generate more to replace the lost output. You can watch it happen in the balancing feed on Grid pulse.

Why it happens

The grid was built for the old geography of generation - big thermal plants near the cities - while most onshore wind was built where the wind is: Scotland. The transmission corridors between the two haven’t caught up, so on the windiest days the wires hit their limits. It is a traffic jam, not a surplus: GB as a whole still wants the power, it just can’t be delivered.

How the mechanics work

Everything settles through the Balancing Mechanism. Each wind farm submits a plan (its physical notification); when the operator needs less, it accepts a bid to reduce output, compensating the farm for revenue it would have earned. The per-farm curtailment figures on Pulse are derived from those accepted balancing actions - which farms, how many megawatts, right now.

The costs are real - hundreds of millions of pounds a year, paid through network charges - which is why curtailment is the loudest argument in GB energy policy.

What fixes it

Four things, all happening at once: new wires (major Scotland-England transmission upgrades are under way), storage that soaks up trapped power (batteries and pumped storage are being built at record pace), flexible demand that migrates toward cheap windy hours (the logic behind the greenest-time signal), and market reforms that price electricity by location.

One honesty note: curtailment numbers here are derived from accepted balancing actions, labelled as such - estimates built on the published record, not a meter inside each turbine.