Spain and Portugal went dark for a day when the Iberian grid lost voltage control

On 28 April 2025, a blackout knocked out power across Spain and mainland Portugal, leaving roughly 50 million people without electricity, in some areas for up to 12 hours. The failure began with a generation loss that rippled through the shared Iberian grid, and the European grid body ENTSO-E's expert-panel final report, published on 20 March 2026, identified gaps in voltage and reactive-power control as central to how a single fault became a continent-scale collapse.

The Iberian system had been running on an unusually high share of wind and solar power. ENTSO-E found that when a large block of generation was lost, the system's reactive-power and voltage-control reserves proved insufficient to hold voltage up, and the resulting voltage collapse disconnected production units one after another. Rail, air traffic, hospitals on backup power and water supply were all disrupted as the grid shed load.

The report stressed that losing a few units should never be able to take down a whole synchronous area. The gap was not in any single decision but in the cumulative effect of years of change — a growing share of inverter-based renewables that provide little of the inertia and voltage support that conventional plants once supplied — without the control framework having been upgraded to match.