Grid collapse across Spain and Portugal on the Iberian Peninsula
Apr 2025Published 1 May 2026Responsible editor: Chief Editor
- Where
- Iberian Peninsula covering Spain and Portugal
- What
- System collapse with 60 percent of national demand lost in five seconds
- Cause
- Under investigation
- Outcome
- 92 percent of supply returned by early the following morning
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What happened
In April 2025 a system collapse affected the Iberian Peninsula, a synchronously connected region in south-west Europe covering Spain and Portugal. Public reporting stated that around 60 percent of national demand in Spain, the larger of the two countries, was lost within about five seconds, leading to a full system collapse, with Portugal affected at the same time. National authorities described the event as exceptional. Restoration began the same day and continued overnight, with reporting indicating that around 92 percent of supply had been returned to customers by early the following morning.
Millions of households and businesses were affected, along with transport, health and government services in both countries. Recovery activity, including power quality stabilisation, restoration of communications and staged industrial restarts, continued for several days. The sequence that produced the collapse became the subject of a formal multi-country investigation coordinated by the European association of transmission system operators. The event is among the largest synchronous grid disturbances in Europe in the past decade and prompted renewed attention to voltage control margin, defence plans and restoration capability.
Contributing factors
Drawn from public reporting and investigation material available at the time of writing, and to be read as provisional until the final investigation report is confirmed: (1) voltage instability across the Iberian Peninsula, the synchronously connected region covering Spain and Portugal, was reported as central to the collapse mechanism, propagating rapidly across the network; (2) the reported speed of the cascade, around 60 percent of national demand within about five seconds, was described as exceptional; (3) the operating regime at the time was reported to include a high proportion of inverter based generation relative to synchronous machines providing voltage support; (4) reactive power management and voltage control arrangements at transmission, distribution and generator level were reported as areas under formal examination; (5) protection system behaviour during the rapid cascade was also reported as an area under examination. No final attribution of cause should be inferred from this entry.
Lessons learned
- Voltage instability can propagate across a synchronous area in seconds when inverter based generation forms a high share of the operating regime, so operators should review reactive power margins and grid forming capability in those conditions.
- Defence plans must act within the timescale of a fast voltage cascade rather than legacy response times, so test load shedding and islanding schemes against five second demand loss events.
- Protection settings require review for fast voltage excursions to avoid premature tripping or delayed clearance during rapid cascades.
More lessons on spacing, layout and fire spread, electrical protection and isolation, from every incident on the register.
Not yet known
- Final cause from the multi-country investigation
- Cost of the outage and restoration
- Exact share of inverter based generation at the time
This entry is updated when these are reported. Get an alert for the next one like it.
Source
Published 2026-05-01. Written from public reporting. Descriptive, not investigative. See the data accuracy disclaimer.
