Grid management systems, renewable energy forecasting
In theelectric power industry,curtailment is an involuntary reduction of the electric generator output ("dispatch down") made to maintain grid stability (for example, ingrid 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. Thesevariable renewable energy plants, due to the absence of an expendable resource (like fuel), have quite lowmarginal 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 impactpower 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]
AfterERCOT built a new transmission line from the Competitive Renewable Energy Zone in West Texas to the central cities in theTexas Interconnection in 2013, curtailment was reduced from 8-16% to near zero.[8]
In 2018, curtailment in theCalifornia grid was 460 GWh, or 0.2% of generation.[10] Monthly curtailment has since increased[4][11] to 150-300 GWh in 2020 and 2021[12][13] and to 500-700 GWh by 2024/2025, mainly in spring, although 11 GW of batteries also timeshifted some of the surplus power.[14][15] Curtailments mainly happen forsolar power at noon as part of theduck curve.[16]
In Hawaii, curtailment reached 20% on the island of Maui in Hawaii in the second and third quarters of 2020.[17]
In Ireland, 1.2 TWh of wind power was curtailed in 2022.[18] In United Kingdom, 1.35 TWh of wind power was curtailed in early 2023.[19] In Australia, 4.5 TWh of solar and wind power was curtailed in 2024.[20] In the 2 years from October 2022 to September 2024, 2.9% ofsolar power in Spain was curtailed.[21] In 2025in the Cyprus grid, almost half of distributed large scale solar power was curtailed.[22]
Curtailment in Texas, 2007-2014
Monthly curtailment in California 2015-2024
Solar power and curtailment in California, by hour
^abPyper, Julia (9 May 2019)."Electric Ridesharing Benefits the Grid, and EVgo Has the Data to Prove It".www.greentechmedia.com.Archived from the original on 18 October 2020.the cumulative annual load profile by hour of LDV fleets using its fast charging network — with rideshare vehicles currently making up the lion's share on a gigawatt-hour basis — aligns with the cumulative solar curtailment by hour on the CAISO system
