Iberia’s Day-long Blackout

Dear Readers,

I am in Portugal now. I am having a short family break while learning Portuguese and annoying the locals :) Learning Portuguese is tricky, but I speak it whenever possible.

What happened

My plan was to send my emails yesterday. On Monday, however, we had a total blackout. Around 12:30 p.m. on Monday, the entire Iberian Peninsula went dark. For roughly twelve hours, almost 60 million people in Spain and Portugal—plus pockets of southwestern France—lost grid power, forcing airports, hospitals, and rail hubs onto emergency generators and confusing city centres.

As we read at the wired.com, The Agonizing Task of Turning Europe’s Power Back On, according to national grid operators Red Eléctrica (Spain) and REN (Portugal), electricity supply collapsed “in milliseconds” after abnormal frequency oscillations rippled through the European synchronous grid. The blackout spread across Spain, Portugal and limited parts of Occitanie in France.

The leading theory

We don’t know yet what really happened. There is a lack of information at this very moment.

The main suspect of the blackout is a grid oscillation. A grid oscillation is a rhythmic back-and-forth swing in one of an electric power system’s key parameters—usually frequency, but sometimes voltage or power flows. Think of it as the electrical equivalent of a large suspension bridge that has started to sway: a little movement is natural, but if the oscillation grows or lasts too long, components begin to trip to protect themselves, and the whole structure can collapse.

A grid oscillation isn’t just a harmless flicker in the numbers—it’s the sign of a tug-of-war between generation and demand that, if left unchecked, can trip equipment, fragment the network, and plunge entire regions into darkness. That’s why power engineers treat frequency swings measured in a few tenths of a hertz as a five-alarm fire—and why robust damping controls and real-time monitoring are at the heart of modern grid reliability.

Update, October 2026: The follow-up investigations are in, and the confirmed cause was more specific than a generic frequency oscillation. Spain’s government-appointed inquiry, presented in June 2025, ruled out a cyberattack and traced the collapse to a chain of voltage failures: too little dynamic voltage control had been scheduled for that day, so when voltage rose too high in southern Spain, several generating plants (solar farms among them) disconnected to protect their own equipment, and the resulting imbalance cascaded into the full blackout (Council of Ministers press briefing, La Moncloa, 17 June 2025). ENTSO-E’s independent expert panel reached a similar verdict in its final report, published in March 2026: no single cause, but a systemic mix of inadequate voltage control and insufficient grid-planning margins—oscillations were part of the cascade, but not, as I suspected here in real time, the root trigger.

Riding it out

We survived without electricity, thanks to the hotel’s organisation, which considered using a backup generator to help us stay as comfortable as possible.

The lights were mostly back on this morning, but the investigation into why the outage happened has only just begun.

How did it go without electricity?

It was chaos! Some people became so stressed out that they could not drive well. The long-distance trains were halted, and airports had cascading delays as baggage belts, jet bridges, and some radar systems went offline. The supermarkets were closed because they could not process the payments and cope with the stress of shopping.

Lessons for grid design

What happens next? I hope this event will not be repeated in the future. I saw how much panic it can cause people and how it can tremendously disrupt our lives. Technical grid design must also be improved to improve grid redundancy in the case of future outages.

What can we do about future outages?

Having experienced an outage like this for the first time on this scale, I honestly recommend everyone to:

1. “Expect the unexpected” (thanks, Nick, for the great expression!) and be prepared that everything we take for granted might become unavailable. Water and electrical power are our basic luxuries, which might quickly become scarce in case of events like blackouts.
2. Keep battery packs charged. Have generators if possible.
3. We need to have some food supply (we had tuna pâté and some nuts and crackers, and we avoided long waits in the hotel restaurant, which had difficulties feeding so many people with limited resources) and WATER at home.
4. Be prepared to walk the stairs, and do not use lifts if possible.
5. Have a bit of cash for these cases handy.
6. Prepare your emergency medications pack to keep you running for at least a week.
7. Wear comfortable shoes in case you have to walk long distances.
8. Have some candles prepared for a romantic touch :)

Final thoughts

To manage blackout stress, remember to breathe deeply and stay calm; everything is temporary, and this too shall pass. Good luck!

References

• The Agonizing Task of Turning Europe’s Power Back On, Wired
• Council of Ministers press briefing on the blackout report, La Moncloa, 17 June 2025
• 28 April 2025 Iberian Blackout – Expert Panel Final Report, ENTSO-E