Apr 28, 2025 1:26 PM

A massive blackout affecting Spain, Portugal and parts of France has been blamed on atmospheric conditions. Now engineers face the arduous task of getting the power back on.

Photograph: Diego Radames/Getty Images

At 12:30 pm local time on Monday, the power went out. Across Spain and Portugal trains, planes, and traffic lights abruptly stopped working.

Reports emerged of people being stuck in lifts, and Google Maps live data showed traffic jams in big cities, including Madrid and Barcelona, as they became gridlocked. Major airports warned passengers of delays due to the blackout. Its cause is still unknown. The blackout is estimated to have affected the entirety of Portugal and Spain and small regions in France.

“Traffic lights aren’t working. The streets are chaotic because there is an officer at every crossing,” says Gustavo, who lives in Madrid. “Water doesn’t reach flats at the top of buildings because the pumps are electric, and the very few shops that are open are only taking cash.”

This is every electrical engineer’s nightmare scenario, says Paul Cuffe, assistant professor of the School of Electrical & Electronic Engineering at University College Dublin. “The reason we don’t have widespread outages all the time is because system operators are very conservative and very proactive about using big safety margins to make sure this doesn’t happen,” he says. Engineers plan for failures in grids or surges in consumer demand that could destabilize the power supply. “These things are unusual, but to a power engineer the latent threat of it happening is always there.”

Spain’s electricity operator Red Eléctrica said in a post on X a few hours after the initial blackout that it had recovered power in some areas of Cataluña and Aragón in the northeast; País Vasco, Galicia, La Rioja, Asturias, Navarra, and Castilla y Léon in the north; Extremadura in the east; and Andalucía in the south.

Experts believe that getting the grid back up and running in both countries could take between a few hours to several days, depending on the area. While the grid is powering back up, emergency services will likely be prioritized over things like stable internet connection, they say.

There is a well-rehearsed sequence of steps that now happens, says Cuffe. They are going to be doing what is called a “black start”—a process that gradually reconnects power stations to form a functioning grid again. Electrical supply and demand has to be balanced to avoid further blackouts, meaning as power stations come online, only portions of the grid can come online with them, with the country gradually powering up, step by step. There should be a team within the grid operator that plans for this and that has identified which generators to bring online first, he explains.

“You should be anticipating every failure that can happen and you should survive any one of them,” Cuffe says. From the control room, engineers should be able to tell what parts of the grid are definitely functioning so they won’t be flying blind—but it will still take time.

“Even with a completely healthy grid, to do that black start could take 12 hours or 16 hours. You have to do it sequentially, and it takes a long time. I’m sure there are engineers in vans swarming all over the place as we speak trying to make all this happen.

“It’s like assembling some hellishly complicated IKEA furniture.”

The biggest issue is that without an established, obvious cause for the blackout in the first place, it will be difficult for engineers to know where to re-establish power first without triggering another outage.

“The challenge is to constantly match supply and demand,” says Ketan Joshi, an independent climate and energy consultant. “You need to perform that balancing act, not just plugging everything back in there.” Joshi describes it as a blackout “in reverse.”

“When a tree falls on a power line you end up chopping off a small chunk of the grid. It’s a pain. A hundred homes get blacked out, a crew comes and they re-energize and reconnect the section that was disconnected,” Joshi explains. This is the same thing, but at an enormous scale. “When you have a blackout like the one we are seeing in Spain and in Portugal, the challenge to map supply and demand becomes ridiculously complicated. Every time you connect up a new chunk of households, you have to perform that same balancing act. The generators that are producing electricity have to match the new demand that has suddenly come on to the grid.”

REN (Red Eletrica Nacional) the main power operator in Portugal, gave a statement to the BBC saying that the outage was caused by “extreme temperature variations in the interior of Spain, there were anomalous oscillations in the very high voltage lines (400KV), a phenomenon known as ‘induced atmospheric vibration’.” Spain has yet to respond to this allegation.

“I scratched my head at that,” says Cuffe. Both of the country’s grids may be run by national operators, he explains, but they are shackled together as a synchronized grid, which means if one side fails the other one does too—making it not entirely unexpected for one to blame the other.

When it comes to propping the grid back up, both operators are on their own. The Iberian peninsula is an “energy island,” says Jan Rosenow, vice president of global strategy at the Regulatory Assistance Project, a NGO advancing policy innovation and thought leadership within the energy community. Spain and Portugal’s collective interconnection capacity with the rest of Europe—that is, how much of their energy they can draw from or send into the wider continent—is around 6 percent, far lower than the 15 percent target set by the European Union by 2030.

“There’s a lot of speculation at the moment, but perhaps with better interconnection the problem would have been a lot less worse,” he says.

In a press conference, Spanish president Pedro Sánchez said that the cause of the power cut is still unknown and warns against speculation. He claimed that the regions that have recovered power have done so with the assistance of connections with France and Morocco, and confirmed that the hydroelectric plants in Spain are back online. He claims that hospitals are unaffected by the power outage, and that air traffic had been “voluntarily” reduced by 20 percent during this incident. He said that trains will be halted for security reasons.

Blackouts in Europe do not happen frequently—a blackout across the whole of Italy in 2003 is the closest example that experts cite as having a similar scale to the one affecting the Iberian peninsula: a tree brought down a line between Switzerland and Italy, causing other lines close by to take over the power from the failed line and overload. This caused a blackout for 18 hours that plunged over 55 million people into darkness.

At the beginning of the current blackout, things seemed more or less normal, says Daniel Borrás, head of editorial content at WIRED’s sister publication GQ, who is based in Madrid. “People understood that it would be a couple of hours, or something like that. Now the feeling is a little different because a lot of communities in Spain are recovering step by step, for example Cataluña and Galicia, and Pais Vasco are more or less working, but in Madrid it’s basically still a complete blackout. A lot of people are in the streets and in the bars and the terraces drinking something and it’s a very quiet mood.”

The main issue where he is, says Borrás, is with people trying to come back into Madrid and finding themselves in terrible traffic because trains aren’t running.

“No one has lost their sense of humor, and people are going out to enjoy some digital disconnection,” says Gustavo. He says he’s on his balcony enjoying a good book and contemplating going out to buy candles. “I’ll need a couple of hours to decide whether I should get lavender vanilla spa or geranium.”