Do solar panels work during a power cut?
On 28 April 2025, thousands of homes in Spain with panels on the roof went dark just like everyone else. We explain why it happens, how to tell whether your system would keep working, and what your alternatives are if it wouldn't.
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The short answer
In most cases, no. A standard grid-connected solar system switches off automatically as soon as the power goes, even on a perfectly sunny day. And it's not a fault: the regulations require it.
Only systems with batteries and an inverter with a backup function (called backup or EPS), able to separate the house from the grid and power it on its own, keep working. The vast majority of systems installed in Spain aren't set up for this.
Why solar panels switch off when the power goes
When the grid goes down, engineers are out working on the lines to restore supply. If your system kept feeding electricity into the grid, it could electrocute them. That's why grid-connected inverters must have anti-islanding protection: they detect the loss of voltage and stop producing instantly.
In Spain this requirement is part of the rules on self-consumption, Royal Decree 244/2019, and of the technical standards inverters must meet. Any inverter sold in Spain for grid connection has this protection. The same applies across the EU and in the UK.
The same goes for balcony solar kits: their micro-inverters also have anti-islanding protection and switch off during a power cut.
Which systems work and which don't
| Type of system | Works in a power cut? | Why |
|---|---|---|
| Grid-connected panels, no batteryThe most common | No | The inverter disconnects because of anti-islanding protection. |
| Panels with a battery but no backup function | No | The battery is there, but the inverter can't power the house without the grid. |
| Panels with a battery and a hybrid inverter with backup or EPS | Yes | It isolates from the grid and powers the backup circuits from the battery and the sun. |
| Off-grid system, not connected to the gridCountry houses, cabins | Yes | It doesn't depend on the grid, so a blackout doesn't affect it. |
The second case is the one that caught most people out in April 2025: many had paid for a battery thinking it would protect them from outages, only to find their system wasn't configured to run without the grid.
How to tell whether your system would work in a power cut
Check whether you have a battery
Without a battery, your system won't work in a power cut. In good sun, a few very specific inverters can power an emergency socket without a battery, but they're uncommon and the supply isn't stable.
Find your inverter model
It's usually on a label on the unit itself or in the paperwork from your installer. In its spec sheet, look for terms such as "hybrid", "backup", "EPS" or "off-grid".
Check for a backup circuit
Even if the inverter supports it, it must be wired and configured. There's usually a separate board or line for "essential loads".
Ask your installer
It's the surest way to know. Ask directly: "If the power goes, does my system keep supplying electricity? To which sockets?". If you're not confident in Spanish, write the question down and send it by email.
How to adapt your system to work without the grid
It's possible and fully legal, as long as an authorised installer does it and it meets the regulations. The upgrade usually includes:
- A hybrid inverter with backup function, if yours doesn't have one.
- Batteries to store energy and have supply at night.
- A switching system that separates the home from the grid during the cut.
- An essential loads circuit: fridge, lights, router and some sockets.
According to installers in the sector, preparing a system to run in island mode can add 20 to 30% to its cost, and a complete home battery usually costs several thousand euros. Always get quotes from more than one installer and ask which circuits will be covered.
The no-works alternative: a power station with a solar panel
If you don't have panels, you rent, or you don't want to spend thousands adapting your system, there's a much simpler option: a portable power station with a folding solar panel.
- No installation or permits needed: it isn't connected to the home's wiring, so anti-islanding rules don't apply.
- Works from the first second: models with a UPS function switch to battery in about 10 milliseconds.
- Recharges from the sun during a long cut, with a panel on the terrace or at a window.
- Costs a fraction of a home battery, and you can take it with you if you move.
The trade-off is that it doesn't power the whole house, only what you plug into it. For a power cut, the essentials (fridge, router, lights, phones) fit in a 1 to 2 kWh station. Work out what you need with our calculator and choose a model in the power station comparison.
See portable solar panels See power stations
Have, or planning, solar panels? As well as preparing for outages, check your electricity tariff: not every supplier pays the same for the energy you export to the grid. See Octopus Energy's self-consumption tariffs in Spain.
Frequently asked questions
Why didn't my solar panels work during the blackout?
Because grid-connected inverters must disconnect when they detect an outage, so they don't endanger the engineers repairing the grid. This protection is called anti-islanding and every grid-connected self-consumption system has it.
If I have a battery, will I have power during a blackout?
Only if the inverter has a backup function (backup or EPS) and the system is configured for it. Many systems with batteries don't, and switch off anyway during a cut.
Is it legal for my system to run without the grid?
Yes, as long as the system is designed to isolate itself from the grid during the cut, is installed by an authorised installer and meets the regulations. What's not allowed is feeding electricity into the grid while it's down.
Can I charge a power station from my roof panels during a blackout?
Usually not, because your system's inverter switches off. That's why power stations are paired with their own portable solar panel, which charges them directly without going through the home's wiring.