Why does plug-in solar switch off in a power cut?
A plug-in kit is a grid-tied generator. The law defines a plug-in microgenerator as one “designed to operate in parallel with a distributor’s network” (SI 2026/848). It generates alongside the grid and depends on the grid being there.
Grid-tied inverters have loss-of-mains protection (also called anti-islanding). When the mains supply disappears, the inverter stops exporting. Without it, a generator in your home could keep a section of wiring live during a cut. That’s a hazard to anyone working on the network, or on your own installation.
How this is checked for plug-in kits
It’s part of the type testing. The product specification requires manufacturers to type test the device “in accordance with G98 requirements” and to be assessed as Compliant on the ENA Type Test Register before selling it (IPS §7).
Ofgem’s decision on the G98 change lists what plug-in devices are exempt from. The list includes on-site “functional checks on loss of mains protection”, the checks an installer would normally do for a wired system. It doesn’t include the type-testing requirements themselves.
So there’s no on-site check of this protection. You rely on the type test, which is one reason to buy only a kit listed as Compliant. See compliance checklist.
Can a battery keep it running?
Not with plug-in solar. Some solar systems keep running in a power cut because they have a battery and the equipment to run the home, or part of it, off-grid. Plug-in kits can’t do this under the GB rules:
- The legal definition excludes devices “designed to import electrical energy from a low voltage consumer’s installation for the purpose of storing energy for later supply” (SI 2026/848).
- The product specification excludes “plug-in battery systems” and “plug-in solar PV devices integrated with battery systems” (IPS §1).
- Ofgem says plug-in electricity storage devices “remain prohibited from being sold, supplied, or used in the UK”.
More in batteries.
What happens when the power comes back?
How the kit resumes is down to the product, so check the manufacturer’s instructions. If your RCBO or fuse has tripped and you’re not sure why, ask an electrician.
Test your RCBO now and then
The product specification asks you to test your RCBO periodically while the kit is generating (IPS §8.3.4). See safety.
What to use for backup instead
- A portable power station, charged in advance, runs a few essentials (lights, router, phone chargers, perhaps a fridge) for as long as its battery lasts. It isn’t connected to your home’s wiring, so it’s not plug-in solar. Browse power stations.
- A solar panel for the power station lets you recharge it during a long cut, if it’s sunny.
- Standalone batteries are listed under batteries, marked as standalone products, not plug-in solar.
A portable power station beside a wall socket. It powers what's plugged into it, not the house wiring.
Never feed your home's wiring from a battery or generator
Don’t connect a power station, battery or generator to a socket to power the house. That’s outside the plug-in rules, and it’s the hazard loss-of-mains protection exists to prevent.
Plug-in solar vs a power station in a power cut
| Question | Plug-in solar kit | Portable power station |
|---|---|---|
| Keeps working in a power cut? | No, it stops generating | Yes, until the battery runs down |
| Cuts your bill day to day? | Yes | Not really |
| Allowed to feed your home’s wiring? | Yes, if Compliant and registered | No |
The full comparison is in plug-in solar vs power station.
What to do next
- For bill savings, find a Compliant kit on in stock and check your numbers in the calculator.
- Not sure a kit is Compliant? Use the compliance checker.
