Curtailment vs constraint: a plain-English guide to dispatch-down

“Dispatch-down” is the umbrella term for any time a generator is told to produce less than it could.

Curtailment is the system-wide kind. When there’s too much non-synchronous generation (mostly wind) for the whole island to absorb safely, some of it is dialled back. For many newer generators this curtailment is uncompensated.

Constraint is the local kind. When the wires in one region can’t carry the power, generators there are constrained off — and this is generally compensated.

That distinction matters for cost. It’s why we separate the wasted volume from the compensated cost, rather than multiplying one big number by a price.