Curtailment

Curtailment is the intentional reduction of a generator's power output below what it could otherwise produce, ordered by system operators or triggered by market rules when the grid cannot absorb all available generation. It most commonly affects wind and solar plants but can apply to any generation technology.

Key Aspects of Curtailment:

• Causes: Curtailment is triggered by transmission congestion (power cannot be evacuated from the generation area), excess supply relative to demand (especially during low-load, high-wind/solar periods), voltage or frequency stability limits, and minimum conventional generation requirements for system security.
• Renewable Impact: Wind and solar plants are disproportionately curtailed because they tend to be located in resource-rich but grid-constrained areas, produce output that correlates across large regions, and have near-zero marginal cost, meaning they are dispatched first but also the first candidates when output must be reduced.
• Economic Consequences: Curtailment represents lost revenue for generators and wasted clean energy for the system. High curtailment rates (above 5–10%) can undermine the financial viability of renewable projects, discourage investment, and increase the effective cost of energy transition.
• Compensation Mechanisms: Regulatory frameworks vary widely: some jurisdictions compensate curtailed generators at their foregone market price or a fixed feed-in tariff, while others offer no compensation, shifting the economic risk to generators and influencing project siting and grid connection decisions.
• Mitigation Strategies: Reducing curtailment involves grid reinforcement, energy storage (especially batteries for short-duration shifting), demand-side flexibility, improved forecasting, dynamic line rating, and market redesign to better coordinate generation with available transmission capacity.