On 28 April 2025 almost all of mainland Spain lost power for hours. Many people with solar panels discovered that day that their system had switched off too. It was not a fault: that is how a standard system is meant to work.
Why solar panels switch off when the grid goes down
A normal self-consumption system is connected to the grid through a grid-tied inverter. For safety, that inverter must disconnect as soon as it detects the grid has gone (this is called anti-islanding protection).
The reason is to protect the engineers working to restore the supply. If thousands of roofs kept feeding power into a network the engineers believe is dead, they could be electrocuted. So, even on a sunny day, a system without backup stops supplying power during a blackout.
What you need to keep power in a blackout
Three things:
- A battery, so you also have energy at night or when it is cloudy.
- A hybrid inverter with a backup output (often called backup or EPS), able to power the house cut off from the grid.
- A changeover switch that automatically separates your home from the grid when it fails, so the system stays safe.
With these, when the grid goes down the system isolates itself within seconds and keeps running the house from the panels and the battery.
The whole house or just the essentials?
The usual approach is to choose a set of essential circuits: fridge, lights, router, alarm, water pump and a few sockets. That way the battery lasts many more hours.
Running the whole house, including the oven, air conditioning or induction hob, needs a much bigger battery and inverter. For most homes it is not worth it.
Can I add backup to the system I already have?
Often, yes:
- If your inverter is already hybrid, it may be enough to add the battery and the backup unit, if the model supports it.
- If you have a grid-only inverter, you usually need a battery with its own inverter, or to replace the inverter.
Send us the model you have and we will tell you.
Is it worth it?
It depends on what a power cut costs you. In country houses in the Axarquía with a well and a water pump, in homes where someone depends on electrical equipment, or for businesses where a cut means losses, it usually is. If you are only looking to save money, a battery is justified more by your night-time consumption, as we explain in is a solar battery worth it in Spain?.
As a real example, on this home in Valle Niza we installed 10 kW of panels with a 16 kWh battery.
If you want your system to keep working in a power cut, see solar panels with batteries. Our whole team speaks English and Daniel Hill is a native speaker.