The Iberian Blackout: Why Every Card in Your Wallet Stopped Working

Shortly after half past twelve on 28 April 2025, the Spanish electricity grid lost around 15 GW of generation in roughly five seconds — on the order of 60 per cent of the demand it was serving at that instant. The Iberian system separated from the rest of the European grid and collapsed. Mainland Spain and Portugal went dark, along with parts of southern France, affecting something like 55 million people. Most supply came back within about half a day and restoration finished the following morning. By the standards of national infrastructure failure it was short. It was still long enough to teach a lesson that almost no household preparedness list had accounted for.

The Failure Nobody Had on Their List

People expected the lights to go out. They had not expected that money would stop working. Card terminals went dead. Contactless failed. Phone wallets failed. Cash machines either had no power or, where they did, could not authorise a withdrawal because the network they needed to check your balance against was unreachable. Shops that could open at all could only take cash, and many could not open at all — electric shutters, electric tills, refrigeration, lighting. Petrol stations could not pump. The Madrid metro stopped and tens of thousands of rail passengers had to be recovered from stalled trains. Within a couple of hours the difference between a household that was fine and a household that was stuck was often simply whether there was a twenty-euro note in a drawer.

Why Card Payments Are More Fragile Than They Feel

It is worth understanding the mechanism, because it explains why every payment method fails at once rather than one at a time. A card payment is not settled at the till. The terminal contacts the merchant's acquiring bank, which contacts the card scheme, which contacts your bank, which checks and approves. Four parties, several networks, and power required at every hop. Contactless, chip and PIN, and your phone wallet all travel that same chain, so they do not provide any redundancy for each other — they are three doors into the same corridor. The corollary is that a payment outage does not need a blackout at all. The CrowdStrike incident in July 2024 disrupted payments, check-in systems and health services worldwide with the power still on, which is precisely why digital resilience failure appears as a distinct entry in the UK's National Risk Register 2026.

What the Bank of Portugal Told People Afterwards

One of the most striking responses came from a central bank rather than a preparedness organisation. In the aftermath, the Bank of Portugal advised the public to keep a physical money reserve at home, and specifically to hold it in a range of denominations. That second half is the part people skip. During the blackout, shops with no working till could not give change, so a large note was effectively unusable for a small purchase. Anyone holding a single fifty was worse off than someone holding the same amount in fives and tens. When you put cash aside, break it up: a mix of fives, tens and a handful of coins, not one clean note.

How Much, and Where to Keep It

There is no official UK figure to quote, and treating this as a target number misses the point. The useful test is whether your household could buy several days of essentials with no electronic payment at all — a few days of food, fuel for the car, a pharmacy trip, a taxi if you needed one. For most households that is a modest amount, not a safe full of banknotes. Keep it somewhere you can find in the dark without a phone torch, tell the other adults in the house where it is, and put a smaller amount in a bag or the car too, because an outage is just as likely to catch you out of the house as in it. Refresh it occasionally so it does not quietly become money you have already mentally spent.

The Things Cash Alone Does Not Solve

Cash gets you through the shop door. It does not get you light, information or a charged phone, and in Spain those failed in a predictable order. Mobile networks degraded as mast batteries drained, which is a documented fragility rather than bad luck — Ofcom's work on UK mobile resilience has found that only a minority of mobile sites can keep operating for more than a short period on backup power. Broadcast radio, by contrast, kept working, because a transmitter with backup power serves an enormous area and a battery radio needs nothing from the network. A crank or battery radio, a couple of charged power banks and a lantern are the rest of the answer, and none of it is expensive.

The Paper Layer

The second thing that stops working is your ability to look anything up. Account numbers, your bank's fraud line, your insurer, your GP, the neighbour who has a spare key — all of it normally lives in an app on a phone that needs a network. Write the essentials on a single card and keep it with the cash: your bank's phone number and account details, your insurance policy numbers, two or three personal numbers, and the utility emergency numbers. This is the same discipline as keeping a document kit, and it takes about fifteen minutes once. The Spanish experience is full of people who could not do a simple thing — call a bank, reach a relative, prove who they were — because the only copy was behind a dead screen.

Fuel, and the Half Hour of Warning

Petrol pumps are electric, and the payment terminal attached to them needs connectivity. Anyone in Spain who was already low on fuel stayed low on fuel. This one is easy: when a serious weather event is forecast, or you notice a developing disruption, fill up early rather than waiting for the warning light. Keeping the tank above half through the winter costs nothing, gives you a vehicle that can move if it needs to, and — in a modern car with a decent battery — an incidental way to charge a phone. Do not run a car engine in a garage or anywhere enclosed to do it.

What Made the Difference in Practice

Accounts from Spain and Portugal converge on something unglamorous. The households that coped were not the ones with elaborate equipment. They were the ones with some cash in small notes, a radio that worked without the internet, a torch that was where they thought it was, food they could eat without cooking, and a rough idea of what to do. The ones who struggled had every payment method available to a modern consumer and none of them functioning. The gap between those two positions is perhaps fifty pounds and an hour of preparation.

The Wider Point

The Iberian blackout is the clearest recent demonstration that the digital layer of everyday life has its own failure mode, separate from the physical one. You can have a dry house, a full cupboard and a working car and still be unable to transact. Official preparedness advice across Europe has been slow to say this plainly; a central bank said it before most emergency agencies did. Take the hint. Put some cash in a drawer this week, in small notes, next to a card with your important numbers written on it. It is the cheapest piece of resilience available and the one most households are missing.