Solar panels on your roof: why they switch off in a power cut, and what you can do

Why your panels go off

Most home solar in the UK is "grid-tied": it's connected to the mains so you can use the power and export what you don't need.

When the mains goes off, the system switches off too. This is a safety feature, not a fault. National Grid Electricity Distribution, which runs the local network in the Midlands, the South West and South Wales, says:

• solar panels and other home generation have protective systems installed as standard that disconnect them when there's a fault on the network;
• unless your system can run in "island mode", it is designed to shut down during a power outage;
• when power comes back, generation must wait 20 seconds before switching back on, and it does this automatically.

The reason for the protection is the people fixing the fault. If your panels kept pushing power into the street cables, a cable engineers thought was dead could be live. (This explanation is ours; the network operator's guide describes the protection but not the reason in detail.)

Can you keep some power during a cut?

Yes, but only with a system built for it. Be Ready's power cut page says some solar systems with battery back-up can keep essential appliances running, but only if they're designed to work independently of the grid.

National Grid Electricity Distribution describes this as island mode: the system disconnects from the grid and supports chosen circuits, so important things keep running. It says customers with such a system can switch to island mode ahead of a planned power cut.

What this usually means in practice (general information, check with your installer):

• a battery on its own isn't enough; the inverter and wiring have to support back-up;
• back-up often covers a few chosen circuits (for example the fridge, lights and router), not the whole house;
• some systems switch over automatically, some need you to do something, and some don't do it at all.

Adding a battery: what to ask the installer

Get the answers in writing before you pay:

1. Will this system work in a power cut? Yes or no.
2. Does it switch over automatically, or do I have to do something?
3. Which circuits or sockets will have power?
4. For how long, on a full battery, with what I want to run? (Our runtime calculator helps you check their numbers.)
5. Will the panels recharge the battery during a long cut, or only the battery runs?
6. Are you MCS certified? MCS is the UK quality mark for small-scale renewables. Its battery storage page says to check an installer's certification when you get a quote, before you sign and before work starts.
7. Will you tell the network operator about the change, if that's needed?

We don't recommend any system or installer. Quotes and claims vary a lot; ask more than one.

A cheaper option: a portable power station

If you mainly want to keep phones, lights, the router or a medical device going, a portable power station charged before the cut may be cheaper and simpler than back-up wiring. It isn't connected to your house wiring, so there's no back-feed risk. Our power station sizing post covers what size you need, and our portable solar panel post covers what a folding panel can add in a UK winter.

Generators: outdoors only, and never wired in by yourself

The NHS says portable generators can release carbon monoxide, and lists headache, dizziness, feeling sick, tiredness and confusion among the signs. If you notice them, turn the appliance off if it's safe, get outside and get medical advice.

HSENI's other generator tips: use heavy-duty extension leads to plug appliances into the generator, don't overload it, keep it dry, and let it cool before refuelling.

If someone relies on power for medical reasons

Don't rely on rooftop solar. Sign up to the Priority Services Register with your energy supplier; Be Ready says registered customers get advance notice of planned cuts and priority support. Ask your equipment provider how the device works without power, and keep a charged back-up.

Related guides

• Do you need a portable power station for power cuts?
• Power cuts in the UK: what to do
• Power cut kit: what to keep in one box, and how long power cuts last
• Priority Services Register: a plain guide

Free tools

• Power bank and power station runtime calculator
• Power cuts near me

We're an independent UK site, not the government. We check guides against official sources and link to them. In an emergency call 999.

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