Spain's solar curtailment tops 3.8% — worst in Badajoz at 37%

Circe — a private, non-profit research center established in 1993 by the University of Zaragoza, the regional government of Aragon, and utility Endesa — has published findings from a nine-month study of curtailment across Spanish substations. The national average curtailment rate sits at 3.83%, but the distribution is highly uneven across regions.

Extremadura and Castilla-La Mancha record the highest curtailment rates, while Badajoz province alone exceeds 37%. Notably, Andalusia — Spain's largest solar market by installed capacity — does not show comparably elevated figures. Circe stressed that the more relevant question for project developers is not the regional average, but the expected loss at a specific grid connection point.

The analysis identifies three distinct curtailment drivers. First, grid capacity limitations arise when transmission and distribution networks cannot absorb all generated power, particularly in high-renewables, low-demand areas. Solutions include infrastructure upgrades, battery storage, demand-side management, and better spatial planning for new projects.

Second, system security curtailments are triggered by grid disturbances, low inertia, voltage issues, or oscillation risks, and can be addressed with synchronous condensers and STATCOM devices. Third, market oversupply curtailment calls for electrification of industry and transport, scaling up green hydrogen, energy storage deployment, and stronger cross-border interconnections. To support developers, Circe has also built the GenerApp tool, which estimates curtailment risk at any given transmission network node.