Curtailment is when the grid asks a wind farm to reduce output or pause generation so the electricity system doesn’t become overloaded. Think of the National Grid like a motorway: wind farms are trying to join, but if there’s too much “traffic,” some are asked to slow down or stop.
Curtailment happens when:
- There’s more electricity being generated than used (for example, a very windy night with low demand).
- Parts of the network are congested, especially where power flows from Scotland to England and certain transmission routes are “narrower.”
- The grid is undergoing maintenance, reducing how much electricity can safely flow through.
In practice, turbines are adjusted so they spin more slowly or change blade angle to capture less wind — essentially, “make less power for now.”
Developers are usually compensated for cooperating through constraint payments, which can be comparable to (or sometimes higher than) the revenue from selling power at that moment. However, many older land leases did not anticipate constraint payments. In those cases, the developer may receive compensation while the landowner’s income drops when generation is reduced.
Landowners should check their lease agreements to see if they include a share of any constraint payments in the rent. If not, rent could be reduced when generation is curtailed. Because the treatment of constraint payments isn’t always clearly explained in leases, it’s a good idea to get professional advice.
