What is curtailment, and why does it matter for your investment?
Curtailment is the instruction to reduce or stop electricity import or export, regardless of whether your asset is capable of producing. It's the single biggest variable in most grid-connected project financial models.
Curtailment in plain English
When you connect a generator, storage or flexible demand asset to the electricity grid, you join a queue. In Great Britain, this queue follows Last In, First Off (LIFO) rules. If the local network becomes congested, the most recently connected projects are the first to be told to reduce output.
This means that if you're near the back of the queue and there's a lot of capacity ahead of you, you could face significant periods where you're told not to use your grid connection. For a solar farm, that might mean switching off during the sunniest hours. For a BESS, it could mean being unable to export during the most valuable trading windows.
The financial impact isn't just about the volume of energy lost. It's about which hours you lose. Curtailment tends to hit the highest-value export periods hardest, so the revenue impact is often much larger than the headline percentage suggests.
Key concepts
LIFO queue
Last In, First Off. The most recently connected projects get curtailed first. Your queue position relative to other projects at your connection point determines your curtailment exposure.
Headline vs effective
A headline curtailment of 20% doesn't always mean 20% revenue loss. For battery storage, the curtailed hours may align with charging rather than export, reducing the effective impact to 3-6%.
Attrition
Not every project in the queue ahead of you will be built. Some will withdraw, delay, or downscale. Modelling realistic attrition scenarios can dramatically change your curtailment outlook.
Temporal profile
Curtailment isn't uniform across the year. It follows patterns driven by generation mix, demand profiles, and network topology. Understanding when you'll be curtailed matters as much as how much.
Constraint physics
Network congestion is driven by thermal limits on transmission circuits, boundary transfers between regions, and local generation patterns. These are physical constraints, not market rules.
Connection reform
Gate 2, queue management reforms, and changes to connection agreements are reshaping who gets connected and on what terms. The rules are changing fast.
Why getting curtailment right is so hard.
Curtailment sits at the intersection of grid physics, market economics, regulatory policy, and project-specific factors. No single dataset tells the full story.
We built an interactive map of all the systems that interact to determine your curtailment risk.
Not sure if curtailment affects your project?
A 20-minute call is enough to find out. No commitment, no sales pitch.
Talk to Henry