What really caused the 2025 Iberian blackout?

At 12:33 on 28 April 2025 the power went out across mainland Spain and Portugal, and for about ten hours in most of the peninsula it stayed out. At least seven people in Spain and one in Portugal may have died of outage-related causes such as candle fires or generator fumes. Everyone had a theory. The official explanation, still debated in its details, is more technical and more interesting.

Shortly before, more than half of Spain's power came from solar, and the electricity price was slightly negative. Then, in under half a minute, a series of generation trips near Granada, Badajoz and Seville removed 2,200 megawatts. Voltage rose, frequency fell below 48 hertz, automatic load shedding kicked in, and the Iberian system collapsed. The expert panel of the European grid operators ENTSO-E and the regulators' agency ACER said in its final report in March 2026 that the blackout resulted from a combination of many interacting factors: oscillations before the collapse, gaps in voltage and reactive power control, differing voltage regulation practices, and others.

Attribution is where the argument is. Presenting the final report, ENTSO-E's chair said the problem is not renewable energy but voltage control, regardless of the type of generation, and the panel said that even with significantly higher inertia the loss of synchronism would not have been avoided. In June 2025, Red Eléctrica's chief of operations said the blackout would not have happened had conventional plants done their job controlling voltage, while in September 2025 an association of electricity companies told the Senate that Red Eléctrica bore sole responsibility. A June 2025 Spanish expert report found no evidence of a cyberattack.

The restart began with a hydro plant able to start itself, without needing power from the grid.