Curtailment (electricity)

• 1. Introduction

  ›

  In Cyprus in 2025, curtailment claimed almost half of large-scale solar power before it could reach any home. Grid operators issued the order to keep the electricity system stable. Curtailment is an involuntary reduction in a power plant's output; the industry calls it "dispatching down." Grid operators have used the technique throughout the history of electric power production. In the 21st century, though, curtailment has become a pressing economic problem for owners of wind and solar plants. Understanding why starts with a fundamental difference between renewable power and everything that came before it.

  2134

• 2. The Renewable Difference

  ›

  A conventional plant ordered to reduce output at least saves on the fuel it would otherwise burn. Wind turbines and solar panels have no such offset. The wind keeps blowing; the panels keep absorbing sunlight. No fuel expense is avoided when a renewable generator is told to stop.

  Variable renewable energy plants carry quite low marginal production costs precisely because they burn nothing. When they are ordered to dispatch down, they lose revenue without saving any comparable expense. This makes curtailment a far more damaging event for a renewable plant than for a conventional one.

  Power purchase agreements, the contracts guaranteeing operators a set price for each unit delivered, are at risk when curtailment becomes routine. A plant that delivers less than its contracted volume faces commercial consequences that extend far beyond any single lost hour. The scale of those losses has grown as renewable energy has spread to every corner of the globe.

  134

• 3. The Global Toll

  ›

  In western China in 2018, around 20 percent of wind power was curtailed before it could reach any user. On the island of Maui in Hawaii, curtailment reached 20 percent in the second and third quarters of 2020.

  Ireland recorded a loss of 1.2 terawatt-hours of wind power in 2022. The United Kingdom curtailed 1.35 terawatt-hours of wind in early 2023. Australia lost 4.5 terawatt-hours of solar and wind power across 2024.

  Spain's record from October 2022 to September 2024 shows 2.9 percent of solar power curtailed. Greece discarded 0.9 terawatt-hours in 2024, then 2 terawatt-hours of green power in 2025. California tells a story of its own, where the time of day matters as much as the volume of generation.

  815161718

• 4. California's Midday Problem

  ›

  California's grid curtailed 460 gigawatt-hours of electricity in 2018, a figure that looked modest at just 0.2 percent of total generation. It did not stay modest.

  By 2020-2021, monthly curtailment in California had climbed to 150-300 gigawatt-hours. By 2024-2025, the monthly figure ranged from 500-700 gigawatt-hours, with spring months driving most of that volume. The state had added solar capacity faster than demand could absorb it.

  The pattern behind this surge is called the duck curve. At noon on a spring day, solar generation peaks while overall electricity demand holds relatively flat. The grid floods with power it has nowhere to send. California deployed 11 gigawatts of battery capacity to time-shift some of that surplus. Yet the midday problem persists, and solving it at scale requires more than storage alone.

  101214139

• 5. Building a Way Out

  ›

  In 2013, ERCOT completed a transmission line from the Competitive Renewable Energy Zone in West Texas to the central cities of the Texas Interconnection. Curtailment in that corridor fell from 8-16 percent to near zero. Transmission upgrades are one of four approaches grid operators can use to reduce curtailment.

  Better forecasting for electricity prices, wind, and solar output helps operators anticipate imbalances before a curtailment order becomes necessary. Demand response programs shift electricity consumption toward periods when generation is high. Increased energy storage captures surplus for later delivery. Together, these tools can reduce curtailment or avoid it completely.

  Using all available energy can require methods as costly as building new power lines or adding storage capacity. When those costs exceed the value of the electricity being saved, operators may find it cheaper to let the surplus go. That calculation will grow harder to avoid as renewable generation continues to expand across every major grid.

  7361924