The power grid in Europe, specifically in Spain, Portugal, Andorra, and parts of southern France, experienced a major outage on April 28, 2025, starting around 12:33 p.m. CEST. The primary cause, according to Portugal’s grid operator Redes Energéticas Nacionais (REN), was a “rare atmospheric phenomenon” involving extreme temperature variations in Spain. This led to “anomalous oscillations” in high-voltage (400 kV) lines, a phenomenon known as “induced atmospheric vibration.”

These oscillations caused synchronization failures across the interconnected European grid, resulting in a cascading disconnection of power systems. Spain’s grid operator, Red Eléctrica, reported a sudden loss of 15 gigawatts—60% of Spain’s electricity demand—in five seconds, which triggered the collapse of the Iberian Peninsula’s grid.

A contributing factor was a technical issue with the France-Spain interconnector, which disconnected Spain’s grid from the broader European system, exacerbating the outage.

Some experts and reports have also raised the possibility that Spain’s heavy reliance on renewable energy, particularly solar and wind (which supplied over 80% of electricity before the outage), may have strained the grid. The rapid expansion of intermittent renewables, combined with insufficient grid upgrades, can create instability, especially under extreme conditions. A 2022 ENTSO-E report warned that low-inertia renewable sources reduce the grid’s ability to balance power during disruptions. However, no definitive evidence confirms renewables as the sole cause.

Initial speculations about cyberattacks or sabotage were dismissed by officials, including European Commission Executive Vice President Teresa Ribera and European Council President António Costa, who stated there was no evidence of deliberate interference. The EU Agency for Cybersecurity suggested a cable fault as a possible trigger, though investigations are ongoing.

The outage caused widespread disruption, halting trains, metros, traffic lights, and telecommunications, closing airports like Lisbon’s, and forcing hospitals to rely on generators. By early April 29, nearly 90% of Spain’s power and most of Portugal’s was restored, but full normalization could take days, with some estimates suggesting up to a week for Portugal.

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