The ENTSO-E Expert Panel has published its factual report into the 28 April blackout that cut supply to continental Spain and Portugal in the most serious power system event in Europe in more than two decades.
The investigation found the incident began at 12:33 CEST when voltages in southern Spain rose sharply and spread into Portugal, triggering a cascade of generator trips and a rapid frequency decline.
The Iberian Peninsula lost synchronism with the rest of the Continental Europe synchronous area at 12:33:19, with interconnections to France and Morocco tripping shortly afterwards. By 12:33:24 all system parameters in Spain and Portugal had collapsed.
The panel said automatic system defence plans activated but could not prevent the full outage.
Restoration was achieved through a mix of re-energisation from France and Morocco and black-start hydropower in Spain and Portugal, with Portuguese supply restored by 00:22 on 29 April and Spanish supply by 04:00.
The report noted the Iberian system had been operating normally before the incident, with regional coordination centres identifying no security risks and the grid considered “N-1 secure”.
It added the event was the first time in the Continental Europe synchronous area that a combination of cascading generator disconnections and voltage rises triggered a system-wide blackout.
A final report due in the first quarter of 2026 will provide a root-cause analysis and recommendations to prevent recurrence.
SolarPower Europe, UNEF and APREN welcomed ENTSO-E’s factual report.
The groups said the report highlights a lack of voltage control as a key system condition at the time of the incident.
They noted renewables were not legally permitted to contribute to voltage control until Spain updated Operational Procedure 7.4 on 12 June 2025.
The organisations said full implementation of the new rules in the coming months would enable a more robust system.
In a joint statement they added: “The Iberian blackout must be a moment of learning. These technologies are already available and should be procured to further support stable voltage levels, managing variability, and delivering renewable-powered energy security.”
They reiterated calls for greater investment in system stability and flexibility, including allowing renewables to provide dynamic voltage control and integrating battery storage and grid-forming inverters.
ENTSO-E is preparing a final report for the first quarter of 2026 with root-cause analysis and recommendations.