Curtailment (electricity)

For other uses, see Curtailment.

Curtailment is the deliberate restriction of power output from renewables, often due to oversupply, low demand or grid constraints.^[1][2][3] Solar power producers may for instance reduce their output at midday if there is a lot of other solar capacity in the system. Wind power may be curtailed in months with less energy demand.^[4] Economic curtailment is the most common, where producers scale down in response to low wholesale electricity prices.^[5]

Curtailment is a loss of potentially useful energy, and may impact power purchase agreements.^[6][7] 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.^{[8][9][10][11]}

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.^[12]

Curtailment of wind power in western China was around 20% in 2018.^[13]

In 2018, curtailment in the California grid was 460 GWh, or 0.2% of generation.^[14] Curtailment has since increased^[8][15] to 150-300 GWh/month in spring of 2020 and 2021,^[16][17] mainly solar power at noon as part of the duck curve.^[18]

In Hawaii, curtailment reached 20% on the island of Maui in Hawaii in the second and third quarters of 2020.^[19]

In Ireland, 1.2 TWh of wind power was curtailed in 2022.^[20] In United Kingdom, 1.35 TWh of wind power was curtailed in early 2023.^[21] In Australia, 4.5 TWh of solar and wind power was curtailed in 2024.^[22]

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

Mitigation options

• Transmission upgrade^[12]
• Demand response^{[8][23][18][24]}
• Battery storage power station
• Energy forecasting, including forecasting for price, wind and solar