Curtailment (electricity)

For other uses, see Curtailment.

In the electric power industry, curtailment is an involuntary reduction of the electric generator output ("dispatch down") made to maintain grid stability (for example, in grid balancing). While curtailment is a standard technique that has been applied throughout the history of electric power production, in the 21st century it has become an economic issue for the owners of wind and solar generation plants. These variable renewable energy plants, due to the absence of an expendable resource (like fuel), have quite low marginal electricity production costs, so curtailment affects the economics of projects in a much more significant way than with conventional units.^[1]

Curtailment is a loss of potentially useful energy and may impact power purchase agreements.^[2][3] However, using all available energy may require costly methods such as building new power lines or storage, becoming more expensive than letting surplus power go unused.^[4][5][6][7]

Examples

After ERCOT built a new transmission line from the Competitive Renewable Energy Zone in West Texas to the central cities in the Texas Interconnection in 2013, curtailment was reduced from 8-16% to near zero.^[8]

Curtailment of wind power in western China was around 20% in 2018.^[9]

In 2018, curtailment in the California grid was 460 GWh, or 0.2% of generation.^[10] Curtailment has since increased^[4][11] to 150-300 GWh/month in spring of 2020 and 2021,^[12][13] mainly solar power at noon as part of the duck curve.^[14]

In Hawaii, curtailment reached 20% on the island of Maui in Hawaii in the second and third quarters of 2020.^[15]

In Ireland, 1.2 TWh of wind power was curtailed in 2022.^[16] In United Kingdom, 1.35 TWh of wind power was curtailed in early 2023.^[17] In Australia, 4.5 TWh of solar and wind power was curtailed in 2024.^[18]

From October 2022 to September 2024, 2.9% of solar power in Spain was curtailed.^[19]

• 
  Curtailment in Texas
• 
  Monthly curtailment in California
• 
  Solar power and curtailment in California, by hour

Mitigation options

• Transmission upgrade^[8]
• Demand response^{[4][20][14][21]}
• Battery storage power station
• Energy forecasting, including forecasting for price, wind and solar