On Monday, 28 April 2025, a major power blackout occurred across the Iberian Peninsula affecting mainland Portugal and peninsular Spain, where electric power was interrupted for about ten hours in most of the Peninsula and longer in some areas.
The April 2025 Blackout
At the time of the April 28 event, the Iberian Peninsula was experiencing relatively normal operating conditions. The load was approximately 25 GW in Spain and 8 GW in Portugal. Weather conditions were favorable—sunny with no faults, though there were high winds in the southern peninsula. The system had benefited from a rainy spring, resulting in high hydro reservoir levels. However, several large generators were undergoing seasonal maintenance. Meanwhile, there was significant solar PV generation being supplied to the grid at the time of the incident.
What happened with the power grid in Spain, Portugal, and parts of France on April 28, 2025?
During the early afternoon of Monday, April 28, 2025, the power grid in Spain experienced a cascading event and lost about 60% of its power generation. The sudden 15 gigawatt loss in electricity generation impacted grid frequencies and stability across the integrated Iberian Peninsula grid, leading to a nearly daylong blackout across Spain, Portugal, and parts of southern France. By late Monday evening, Redes Energéticas Nacionais (REN), Portugal’s national electricity and natural gas transmission system operator, had restored 85 of 89 substations in Portugal. Red Eléctrica de España (REE, “Red Eléctrica”), Spain’s national electricity transmission system operator, had restored nearly all demand in Spain by Tuesday morning.
What caused the power grid failure in Europe? (Spoiler: We don’t know yet.)
Understanding the triggers behind a blackout across a large, integrated, diverse network is complicated.
The official causes of the April 2025 power grid failure in Spain, Portugal, and parts of southern France are under investigation. The Spanish government has established a national investigation committee, the European Union’s Agency for the Cooperation of Energy Regulators announced an independent audit (at Portugal’s request), and other investigations are underway. This is similar to the investigation process that occurred following the 2003 blackout in the United States and the subsequent U.S.-Canada Power System Outage Task Force and report.
While official reports are forthcoming, in initial press statements, the Spanish government and Red Eléctrica emphasized that the power outage was not due to renewable energy generation because the system has “worked to perfection with a similar demand situation and with a similar [electric generation] mix” and also ruled out a cyberattack. [1]
However, as sources including the European Network of Transmission System Operators for Electricity (ENTSO-E) have highlighted, the electrical inertia profiles and responses of different generation resources that are part of the grid mix are a key factor in stabilizing grid frequency and voltage during sudden fluctuations or imbalances. Inverter-based resources like solar and wind provide limited frequency regulation compared to other generation (e.g., hydropower, nuclear, natural gas) if not paired with advanced inverters that provide grid-support functions such as synthetic inertia and voltage regulation.
As additional data emerges on the grid conditions at the time of the event, U.S. energy industry stakeholders can learn from recent challenges and leverage future recommendations.