MADRID

A massive power outage that hit nearly all of Spain and Portugal on April 28 may have been caused by a cyberattack or the country’s withdrawal from nuclear energy, according to a top Spanish energy expert.

Yolanda Moratilla, the chairperson of the Committee on Energy and Natural Resources at the Engineering Institute of Spain, said the failure, which left around 60 million people without power for 10 hours, was “technically highly unlikely” and might never be fully explained.

“This event was unprecedented in Europe,” she said, noting that it marked the first time the continent experienced zero electricity production for an extended period.

Spanish Prime Minister Pedro Sanchez and the national power grid operator REE have not provided a timeline for determining the cause. The European Commission’s Energy Union estimates it could take up to six months.

Moratilla said the government and REE had previously claimed that such a blackout in Spain was impossible, but the April 28 incident proved otherwise. She said she had warned of this risk due to Madrid’s plan to shut down all nuclear power plants.

She argued that Spain’s power grid depends on the rotational inertia provided by large steam turbines, typically in nuclear, hydro, coal, and gas plants. But with coal phased out and limited hydro capacity, shutting down nuclear plants has left the country reliant on combined-cycle gas plants, which she said are not enough to stabilize the system.

15 gigawatts lost in 5 seconds

Moratilla said the crisis was triggered by a sudden loss of 15 gigawatts of power, including 10 gigawatts of solar, within just five seconds.

“The system lacked sufficient backup,” she said. The first part of the failure occurred within 3.5 seconds, and the grid could not recover. Nuclear plants had been allowed to stop operating due to low electricity prices, despite rules requiring two to remain online.

At the time of the incident, no hydroelectric plants were operating, and combined-cycle units could not meet the demand. As the frequency dropped below safety thresholds, all generation systems shut down automatically to prevent damage.

Cyberattack possibility

Moratilla said a cyberattack may have played a role, claiming that the technical sequence of the failure does not make sense.

She criticized the Spanish government’s “ideological” stance against nuclear energy and said the blackout demonstrates the need to emulate France’s energy strategy instead.

She also warned that heavy reliance on imported natural gas could lead to further vulnerabilities.

Renewables not to blame

Moratilla said renewable energy is not the problem, but must be integrated responsibly.

“Renewables have many benefits,” she said, but added that Spain ignored warnings not to exceed 70% renewables in the grid. At the time of the blackout, renewable energy made up 78%.

She emphasized that because Spain and Portugal share an interconnected grid, disruptions in Spain affect the entire Iberian Peninsula.

While Portugal’s smaller system can absorb internal issues more easily, a breakdown in Spain spreads across the region.

Moratilla said the 10-hour delay in restoring electricity was typical, as operators had to initiate a “black start” — beginning with independent hydro and gas plants, followed by reconnections to France and Morocco.

She said the northern and southern regions of Spain were restored first, with nuclear plants brought back online after grid stability returned.

Spain’s power infrastructure remains strong, Moratilla stressed, but the rush to dismantle its foundation is the problem.

“One-third of the energy system should come from nuclear before we fully shift to renewable sources,” she said.