On 28 April 2025, electricity failed across mainland Spain and Portugal for most of a working day. Within minutes, both countries discovered something uncomfortable about modern money: the banks were fine, and almost nobody could pay for anything.
Card terminals went dark. Cash machines stopped dispensing. Mobile coverage thinned as base station batteries drained. Shops that stayed open took cash only, and that cash had to already be in your pocket, because the machine that hands it out needs both power and a live connection.
This is the part of digital banking that rarely gets designed for. A bank can be perfectly available and completely unreachable at the same time.
What happens to your bank in a blackout. 43 seconds.
The bank does not break. The last mile does.
Core banking systems sit in data centres with generators, redundant power and failover sites. They are built to survive a regional outage and they generally do. Your account is not lost during a blackout, and no transaction that already settled is reversed.
What breaks is the chain between you and that system. Your phone battery. The mobile mast. The shop's router. The payment terminal. The cash machine's uplink. Every one of those links belongs to somebody else, and almost none of them were built as payment infrastructure.
Availability is measured in the data centre. Usefulness is measured at the counter.MobiBank Editorial
What fails, in the order it fails
- Power
Tills, terminals, cash machines, routers and lighting stop in the same instant. Anything on a small battery keeps going for minutes, not hours.
- The mobile network
Base stations run on backup batteries with a limited window. Coverage thins out progressively, data first, voice later. Backup power at the mast is the real clock on a digital payment.
- Card acceptance
A terminal that cannot reach the acquirer can only approve within narrow offline limits, if the merchant has enabled them at all. Most refuse the sale instead, because the risk of an unauthorised transaction sits with the merchant.
- Cash access
Cash machines need mains power and a live authorisation path. The queues form at whichever machines are still lit, and those empty quickly.
- The banking app
It shows a spinner. The account is intact, the session is not. Nothing in the app can be completed without a round trip to a server.
A power cut and a network cut are different failures with the same result for you. A shop with a generator still cannot take cards if the line is down. A shop with a working line still cannot take cards if the terminal has no power. Payments need both, continuously, at both ends.
Cash works, and that is exactly the problem
In a prolonged outage, physical cash is the only instrument that clears without a network. Several European civil protection agencies now say so openly, and advise households to keep some cash at home as part of basic crisis preparedness.
The difficulty is that the same event which makes cash necessary also stops you getting more of it. Cash is a one shot buffer sized by whatever you happened to be carrying. It is a sensible personal precaution and a poor national payment strategy, and it is not available at all to people who have been moved onto digital payments precisely because they had no reliable access to branches or machines in the first place.
The transactions that still complete
Not everything stops. What keeps working in an outage has one thing in common: the decision to approve is taken locally, on the device in front of you, rather than by a server somewhere else.
Chip cards can be authorised offline for small amounts, within limits the issuer sets, with the transaction stored on the terminal and forwarded once the line returns. Closed systems with their own local records keep serving. Anything that can finish the transaction where it starts will finish it.
Everything else is waiting on a connection, and a connection is the first thing an outage takes away.
Resilience is decided years before the outage
If a payment can only be authorised by a remote server, then the product is only as available as the weakest link between the phone and that server. No amount of app polish changes that. It is settled at the architecture stage, long before the day the lights go out.
That is the problem MobiBank is built around. Alongside the standard connected app, we are developing MobiBank's patented netless channel so that essential banking actions and payments work without an internet connection, starting with Alpha 1. It is not a fallback screen bolted onto an app. It is the reason the platform is designed the way it is.
MobiBank is a banking platform designed for places and moments where connectivity cannot be assumed. The netless capability and the Alpha 1 device are currently in development.
Frequently asked questions
What happens to a digital bank during a power cut?
The bank itself keeps running. Core systems sit in data centres with backup power, so balances, ledgers and settled transactions are unaffected. What stops is your access to them. Without electricity and a network, the app cannot reach the servers, card terminals cannot request authorisation, and cash machines cannot dispense. Your money is safe and, for the duration, unreachable.
Can I pay by card in a blackout?
Sometimes, for small amounts. A chip card can be approved offline by the terminal within limits set by the issuer, with the record forwarded later. In practice most merchants decline card payments during an outage, because the terminal needs power, the merchant carries the risk on an unauthorised transaction, and many terminals are configured to require an online authorisation for every sale.
Do cash machines work in a blackout?
No. A cash machine needs mains power to run and a live connection to authorise the withdrawal against your account. Losing either one stops it. Machines inside buildings with backup generators may keep running, but only while their network link also holds.
Is my money at risk if the bank goes offline?
No. An outage is an access problem, not an accounting one. Transactions that were already authorised remain valid, and your balance is held in the bank's core systems regardless of whether you can see it. Deposit protection in your country is unaffected by a technical outage.
How much cash should I keep at home for an emergency?
That is a question for your national civil protection guidance rather than for a bank. Several European agencies now include a small amount of cash in their standard household preparedness advice, in small denominations, on the basis that card payments may be unavailable for several days.
Related
MobiBank is a Finnish financial technology company building a mobile banking platform for markets where connectivity and infrastructure cannot be assumed. This article is general information about payment infrastructure and is not financial advice.