The Iberian Blackout: 84 Seconds, and What It Exposed

On 28 April 2025, at 12:32, voltage began rising uncontrollably across the Iberian Peninsula's electricity grid. Eighty-four seconds later, Spain and Portugal were disconnected from the continental European network. Tens of millions of people lost power, at midday, on an ordinary Monday.

It was not a war, not a natural disaster, not a cyberattack: that hypothesis was explored and ruled out. It was a cascading technical failure on modern infrastructure, in two developed European countries.

That's precisely why the event deserves close study: it is the most recent and best-documented full-scale test of what happens when the electricity stops. The European expert panel's final report, published in March 2026, runs to 470 pages. This article extracts what concerns a civilian.

The timeline, without the fog

12:32. A rapid, uncontrolled voltage rise begins on the Iberian grid.

The next 84 seconds. Voltage and frequency oscillations, mass disconnections of generation (particularly inverter-based resources), then a cascade of overvoltage disconnections.

12:38. The peninsula loses synchronism with the Continental Europe synchronous area. Around 60% of peninsular electricity demand vanishes within seconds. Portugal, Andorra and parts of southern France are affected.

The rest of the day. Progressive and uneven restoration, relying on the interconnections with France and Morocco and on plants capable of black start. By around midnight, roughly 61% of demand is restored; by the morning of the 29th, more than 90%.

The cause, after a year of investigation. No single culprit. The report concludes a multifactorial chain whose central element was ineffective voltage control. The head of the European body summarised it in a sentence worth quoting for what it rules out: this is not about renewables, it's about voltage control, and nothing in the recommendations could not be implemented tomorrow.

What that means for you: the root cause is a matter for engineers and regulators. The brute fact is that a grid considered reliable, in two EU countries, went down in a minute and a half without warning. That last sentence is the one to keep.

What failed, in order

This is the useful part. Here is what millions of people lost, and the lesson each failure carries.

Payments. Cash machines out of service, card terminals inert. In shops that stayed open, only those with cash could buy anything. No material preparation proved as immediately decisive as a twenty-euro note in a pocket.

Telecommunications. The mobile network degraded quickly and failed in places. Backup batteries at cell sites last hours, not a day. The government asked the population to limit phone use, a sign the network was saturating before it even fell. Many discovered simultaneously that their phone was at 30% and that the charger had become useless.

Transport. Trains and metros stopped dead, passengers stranded in carriages and tunnels. Traffic lights out, city traffic paralysed. Airports disrupted. Emergency services took thousands of calls from people trapped in lifts.

Fuel. Filling stations couldn't pump. This point is systematically missing from preparedness lists: an empty tank cannot be filled during a power cut, and electric vehicles couldn't charge either.

Water. In apartment buildings, the booster pumps feeding upper floors are electric. No power means dry taps above a certain floor, even in a city whose water network is working perfectly.

Information. This is the point that ties the event to the rest of our articles. With no mobile network, no television, no battery radio, people didn't know what was happening, how long it would last, or whether to head home or stay put. The first official statements came hours after the cut. In that gap, rumours (cyberattack, electromagnetic pulse, worse) circulated unopposed.

The five lessons that hold

1. The failure point was cash, not food. Nobody ran out of food in a day. Many couldn't buy any. A reserve of cash in small notes, at home and on your person, is the best cost-to-benefit preparedness action on this entire list. It costs nothing: that money isn't spent, it's relocated.

2. A battery radio beats a dead smartphone. FM broadcasting kept running through most of the event. A battery or crank radio is the only information channel that depends on neither the mobile network, nor your battery, nor a subscription. Cost: a few tens of euros. The same conclusion applies in the other direction: communicating without infrastructure, which we covered in Meshtastic.

3. The half-tank rule. Don't drop below half a tank in routine use. It's a free habit that turns a constraint into room to manoeuvre. Same logic for power banks: charged, not stored flat.

4. Water is stored at home, not at the tap. A few litres per person per day, for three days, in a cupboard. Without power, a building has no water on upper floors.

5. Light, before anything else. The blackout began at midday; it lasted into the night. One reliable light per person, with batteries verified: exactly what our EDC maintenance sheet documents.

What the event says about the 72-hour rule

The European recommendation, echoed by national authorities, invites citizens to be able to hold out 72 hours before help arrives or services are restored.

The Iberian blackout lasted less than that: most restoration happened within twelve hours. That's precisely what makes it instructive: a half-day event was enough to expose every dependency. The people in difficulty weren't short of tinned food; they had no cash, no light, no information, and no way to get home.

The classic preparedness error is sizing for collapse while neglecting the first twelve hours. Yet the first twelve hours are by far the most probable scenario, and the only one most people will ever actually live through.

What the event does not prove

For intellectual honesty, two clarifications.

It validates no political argument about energy. The final report identifies a voltage control problem and a multifactorial chain, explicitly ruling out the "renewables did it" reading. The subject is technical and belongs to engineers and regulators, not commentators.

Nor does it demonstrate the general fragility of modern societies. Power returned within a day, with no collapse of public order and no mass casualties. Institutions functioned. What was missing were individual margins, and that is exactly the area where a civilian can act alone, without waiting for anyone.

The realistic scenario isn't the end of the world. It's half a day without electricity, on a Monday, with no warning. Useful preparedness is what makes that half-day unremarkable.

Where to actually start

Cash in small notes, at home and some on you. The first lesson, and the cheapest.
A battery radio, with batteries stored separately, and the local public broadcaster's frequency written on paper.
Water for three days, a few litres per person per day.
One light per person, tested, with spare batteries.
Tank above half, power bank charged.
A written family rendezvous plan: where to meet and at what time if phones stop working. It's free, it takes ten minutes, and it's what was most missing on 28 April.

Conclusion

The Iberian blackout is the best-documented event a European has for calibrating their preparedness. It doesn't describe a catastrophe: it describes an ordinary day interrupted, and the exact list of what stops working when the power goes.

None of the lessons it delivers is expensive. None requires spectacular equipment. All of them fit in a cupboard, a drawer, and a ten-minute conversation with the people you live with.

Cash. A radio. Water. Light. A meeting point.

Companion sheet: Download the printable A4 PDF

Sources and further reading

ENTSO-E: expert panel final report on the 28 April 2025 blackout (in Spanish): publication of the report and the statement on voltage control.
Agencia SINC: keys to the great blackout (in Spanish). Scientific summary of the final report: voltage control and cascading disconnections.
Analysis of the final report and CNMC recommendations (in Spanish): recommendations, including the 24-hour autonomy required for communication and control systems.
Timeline of 28 April 2025 (in Spanish). Hour-by-hour sequence, disconnection from the European system at 12:38.
One year on (in Spanish): restoration, regulatory and judicial aftermath, lessons learned.
OPRA: Blackout: the new emergencies (in Spanish). Inventory of paralysed services: traffic lights, transport, filling stations, EV charging.