Spanish Grid Operator Rules out Cyberattack in Major Blackout, Points to Solar Power Drop

Despite Red Eléctrica ruling out a cybersecurity incident, Spain’s High Court said it will open an investigation to determine if a cyberattack was the cause.

People wait outside a closed train station, during a major power outage in Barcelona, Spain, on April 28, 2025. Emilio Morenatti/AP Photo

Spanish grid operator Red Eléctrica de España (REE) ruled out a cybersecurity incident as the cause of Monday’s widespread blackout across Spain, Portugal, and parts of France, and pointed to a sudden drop in solar power generation as a possible cause.

The company’s chief of system operations, Eduardo Prieto, said at a news briefing on April 29 that the electricity system suffered a major loss of power generation in southwestern Spain, causing instability that led to its disconnection from the French grid.

He said the affected generation might have been solar, but that it was too early to say for sure.

“We have been able to conclude that there was no intrusion into Red Eléctrica’s control systems that could have caused the incident,” the company’s system operations chief, Eduardo Prieto, told a press conference on April 29, Spain’s La Vanguardia newspaper reported. “The fact that the disconnections occurred in the southwestern peninsular region may suggest that the loss of generation is solar.”

Solar photovoltaic (PV) accounted for 59 percent of Spain’s electricity at the time of the blackout, wind nearly 12 percent, nuclear almost 11 percent, and combined cycle gas plants 5 percent, Red Electrica data showed. In a span of just five minutes, between 12:30 and 12:35 p.m. local time (1030-1035 GMT) on Monday, solar PV generation plunged by more than 50 percent to 8 gigawatts (GW) from more than 18 GW, the data showed.

Electricity was restored to most of Spain and Portugal early on Tuesday.

Despite REE ruling out a cyberattack, Spain’s High Court said on Tuesday that it will open an investigation to determine if a cyberattack was the cause.

Judge Jorge Calama said that although the cause of the events is unknown, “cyberterrorism is among some of the possible” scenarios.

REE said in a statement that it had restored 99.95 percent of demand while Portugal’s equivalent, REN, said that by late on Monday the network was “perfectly stabilized.”

REN said it had to perform a complex “black start” operation to restore electricity supplies, which meant restarting a Tapada do Outeiro gas plant from a total shutdown to restore power to Greater Porto.

A black start involves gradually restarting power plants individually and reconnecting them to the grid.

“This is a process that must be carried out very gradually and carefully to ensure maximum safety and to preserve the greatest possible stability of the national electricity grid,” it said.

French grid operator RTE said that homes in the French Basque Country were without power for a few minutes on Monday, and that all power has since been restored.

The countries have a combined population of more than 50 million people.

In a statement, Net Zero Watch, a British think tank that scrutinizes climate and decarbonization policies, said that grid analysts have suggested a “high likelihood” that the extent of yesterday’s blackout in Iberia was a result of the Spanish grid operating almost entirely on renewables at the time.

“The stability of power grids depends on so-called ‘inertia,’ a resistance to rapid change that is an inherent feature of large spinning turbines, such as gas-fired power stations, but not of wind and solar farms,” the think tank stated.

It added that too much renewable capacity on a grid can “therefore mean inadequate inertia.”

“As a result, in grids dominated by wind and solar, faults can propagate almost instantaneously across grids, leading to blackouts,” it said.

Writing on his blog, energy analyst John Kemp wrote that the region has one of the world’s “highest penetrations of renewable generation from wind and solar” so the blackout will be a “case study of how renewable generators impact on reliability as well as restarting after widespread failure.”

He said that he believed that investigators would probably take “several months to perform a root-cause analysis and determine the sequence of failures” that contributed to the blackout.

He noted that Spain’s nuclear power stations have all been shut down “automatically by passive safety systems which respond to any sign of a loss of power from the grid by dropping control rods into reactor cores to stop the reaction.”

Spain has seven nuclear reactors generating about a fifth of its electricity, according to the World Nuclear Association.

Under Spain’s nuclear phase-out policy, its nuclear fleet is scheduled to shut down by 2035 and the country will rely solely on renewables. The first reactor is planned to be taken offline in 2027.

Power outages on this scale are rare in Europe.

In 2003, a problem with a hydroelectric power line between Italy and Switzerland caused a major outage that left almost the whole of Italy without electricity for about 12 hours.

Reuters contributed to this report.