The short answer
A standard grid-connected solar system does not keep your power on during a power cut — and that is by design, for safety. When the grid goes down, the inverter automatically shuts off to stop your panels feeding electricity back into the network, which protects engineers who may be working on the lines. This safety feature is called anti-islanding and is a requirement for grid-tied systems. To have power during an outage, you need additional equipment: a battery with backup capability (such as a backup gateway or an inverter designed to island), which can disconnect from the grid and run selected circuits from stored energy. Without that, your panels and battery sit idle during a cut, just like the rest of the grid-supplied home.
This surprises many people: a roof full of panels generating power, yet the house goes dark in an outage. The reason is a deliberate safety rule, and getting round it needs specific backup equipment.
Solar in a power cut
- Standard grid-tied systemShuts down — no power
- Why it shuts downAnti-islanding (protects line workers)
- To get backup powerBattery with backup gateway / islanding inverter
- What backup runsSelected circuits, from stored energy
- Tell your installerRaise backup needs at quote stage
Why standard solar shuts down in an outage
It seems counterintuitive that a generating solar system would switch off when you most want power, but there is a sound safety reason:
- Anti-islanding protection: grid-connected solar inverters are required to detect when the grid goes down and immediately stop generating onto the network. This prevents your system creating an 'island' of live electricity on lines that the network operator and engineers believe are dead.
- It protects people: if your panels kept feeding the grid during an outage, they could energise power lines that line workers are repairing, creating a serious safety hazard.
- It is automatic and mandatory: this shutdown is built into compliant grid-tied inverters and is a condition of connecting to the network. It is not a fault — it is the system behaving exactly as it should.
So during a power cut, a standard solar system safely powers down along with the grid, and the home has no electricity until supply is restored — even though the panels could physically generate in daylight.
What you need for backup power
To keep some power on during an outage, you need equipment that can safely disconnect from the grid and supply your home from stored energy. The table compares the common setups.
| Setup | Power in an outage? | Notes |
|---|---|---|
| Panels only (grid-tied) | No | Inverter shuts down for safety |
| Panels + standard battery | No (by default) | Battery also shuts down without backup hardware |
| Battery + backup gateway | Yes — selected circuits | Disconnects from grid, runs key circuits |
| Islanding/hybrid inverter setup | Yes — selected circuits | Designed to run off-grid during a cut |
Indicative comparison for guidance. Sources: Energy Saving Trust; MCS. Backup capability depends on specific equipment and how the system is configured.
Planning for backup if you want it
If keeping power during outages matters to you, the key is to plan for it at the design stage rather than assume any battery will do it:
- Not every battery provides backup: a standard grid-connected battery shuts down in an outage just like the panels. Backup requires additional hardware, such as a backup gateway, or a battery and inverter specifically designed to island.
- Backup usually covers selected circuits: rather than running the whole house, backup systems are often wired to power essential circuits — lights, sockets for a fridge, broadband — to make the stored energy last. The scope depends on how it is set up and the battery's capacity.
- Daylight matters: some backup setups can also recharge the battery from the panels during a daytime outage, extending how long you can run; others rely solely on the energy already stored.
- Raise it at the quote stage: tell the installer that outage backup is a requirement so they can specify compatible equipment and wiring. Adding it later can be more involved than building it in from the start.
For many UK homes, where mains outages are infrequent, the standard grid-tied setup is perfectly adequate and backup is an optional extra. But if you live somewhere prone to cuts, or simply want resilience, the technology exists — it just needs to be specified deliberately.
Frequently asked questions
Why do solar panels turn off in a power cut?
Grid-connected solar inverters are required to shut down automatically when the grid fails, a safety feature called anti-islanding. It stops your panels feeding electricity onto power lines that engineers may be repairing, which could otherwise be dangerous. The shutdown is mandatory for grid-tied systems and is the system working correctly, not a fault.
Can a solar battery power my house in a power cut?
Only if it has backup capability. A standard grid-connected battery shuts down in an outage just like the panels. To run your home during a cut you need additional equipment — a backup gateway or an inverter designed to island — which disconnects from the grid and powers selected circuits from stored energy. This must be specified when the system is designed.
Do I need to do anything to get solar backup power?
Yes — backup is not automatic. You need to ask for it at the quote stage so the installer specifies a battery and inverter with backup capability and wires the essential circuits accordingly. Adding outage backup later can be more involved than building it in from the start, so it is best raised early if resilience matters to you.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific home. They are guidance, not a quotation or guaranteed saving.