Do solar panels work in a power cut?
Usually not. An ordinary grid-connected solar system switches itself off the moment the grid fails, even on a bright day, and stays off until the power comes back. It is a safety rule, not a fault: panels feeding power into the street would put engineers repairing the lines at risk.
In Great Britain the rule is the loss-of-mains protection in the network operators' connection standards (Engineering Recommendations G98 and G99). In the US it is the anti-islanding requirement in IEEE 1547, which inverters are certified to under UL 1741: the inverter must stop within two seconds of losing the grid.
That is frustrating, because the energy is there. A 4 kWp roof in the south of England makes about 14.7 kWh on an average June day and 2.4 kWh in December (about 3,264 kWh a year). A household's essentials, meaning the fridge-freezer, boiler controls, broadband, lights and phones, need about 2.1 kWh a day.
What does keep working
| Set-up | What you get in a cut | Limit |
|---|---|---|
| Battery with a backup gateway | The house, or chosen circuits, runs from the battery, and the panels keep charging it by day. | The battery's output, often 5 to 11 kW, and its size |
| Hybrid inverter with an EPS circuit | One emergency circuit the installer wires, from the battery and panels. | GivEnergy's EPS is 3.6 kW |
| Enphase IQ8 with Sunlight Backup | Essential circuits run straight from the panels in daylight, with no battery. | Daylight only; a few circuits |
| SMA Secure Power Supply (US) | One socket on the inverter works from the panels in daylight. | Up to 2,000 W, daylight only |
| A portable panel and a power station | Nothing is wired to the house, so nothing has to switch off. | The station's size and the panel's watts |
Sources: GivEnergy's EPS guide, Enphase Sunlight Backup, SMA Secure Power Supply.
With a battery and a gateway, the panels change the answer completely. A full 13.5 kWh battery runs those essentials for about 4 days 12 h on its own; with 4 kWp of panels still charging it in June, it keeps going for as long as the weather holds. The home battery calculator works it out for any size, month and region.
Check what you have
- Look for a gateway or backup switch near the meter or consumer unit (Tesla Backup Gateway, GivEnergy Gateway, Enphase System Controller and the like). No gateway usually means no backup.
- Look for an EPS socket or circuit on a hybrid inverter, and find out what it is wired to before you need it.
- Ask your installer what the system does in a cut and whether the backup has been tested. Backup is often an optional extra, so not every battery has it.
- Test it on a calm day by switching off the main supply at the consumer unit, if your installer says that is safe for your system.
Plug-in solar is the same
A plug-in (balcony) kit's inverter also switches off when the grid fails. Only kits with a built-in battery and a separate backup socket give you anything in a cut, and only from that socket. Plug-in solar has what a kit makes and the new UK rules.
The portable route
A folding panel plugged into a portable power station has nothing to switch off, because it never connects to the house wiring. A 200 W panel on the Jackery Explorer 1000 v2 puts back about 0.7 kWh on an average June day in the south of England, and about 0.1 kWh in December. The station itself runs a fridge-freezer for about 14 h 57 min from full.
Solar for a power cut
Portable solar panel. Plugged into a power station, a folding panel keeps working in a power cut when rooftop solar has switched itself off.
Look for: A panel the station's solar input can take (check the voltage range and the connector), and 100 to 200 W for a mid-sized station.
Solar lantern. Light that recharges itself on a windowsill, so a long cut does not eat into the batteries or the power bank.
Look for: A built-in panel plus USB-C charging for dull days, a stated runtime on low, and a handle or hook.
Folding solar charger. For outages that last days, a panel in a sunny window or on a balcony tops up phones and power banks when there is nothing to recharge them from.
Look for: A watt rating (20 W or more is useful), a USB-C port, and realistic expectations: behind glass or under cloud it gives far less.
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The solar recharge guide explains how to match a panel to a station, and every power station page has recharge times by region and month.
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