Curtailment

Curtailment is when a grid operator deliberately reduces output from a generator, most often wind or solar, even though the resource needed to generate more is available. It happens when supply exceeds what the grid can use or move to where it is needed: demand is too low, transmission lines are full, or other plants cannot ramp down fast enough to make room. Curtailed generation never appears in output figures, because it was never produced; it shows up only indirectly, as a gap between a plant's potential and its recorded generation.