Home batteries for power cuts: what to check before you get quotes (UK)
A fixed home battery costs thousands, and not every one keeps your lights on in a power cut. Ask these questions first.
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What it costs
Installed prices we found for a Tesla Powerwall 3 run from about £7,500 to £14,500 (installer price guides, from a search summary read 1 Nov 2026, so less certain). Prices depend on the size, the inverter and the wiring work.
The question that matters most
Most rooftop solar systems switch off in a power cut, on purpose. A battery only helps in a cut if it has a back-up or 'island mode' that powers chosen circuits on their own. Not every battery does. Ask the installer, in writing, whether yours will work in a power cut, what it will run and for how long. Our post explains why: why solar panels switch off in a power cut.
Checklist for quotes
- Is the installer MCS certified? (find an MCS installer)
- Does it give back-up power in a power cut? Which circuits?
- Who honours the warranty if the maker or installer stops trading?
- Will they notify the electrical work under the building regulations (Part P in England)?
- Get at least three written quotes.
Who it's for
Worth a quote: homeowners with solar panels, or who want back-up for medical equipment and can afford thousands.
Not for most people: if you mainly want phones, lights and the router in a power cut. A portable power station costs hundreds, not thousands.
How we judged
We haven't compared battery models; we compared what to ask. We don't recommend any maker or installer.
No star ratings: we haven't collected reviews, and we don't show anyone else's. No product can promise to keep you safe.
Next
Sources
- MCS: find an installer (page, read 1 Nov 2026)
- GOV.UK: Approved Document P (electrical safety) (page, read 1 Nov 2026)
How we review: we read each source on the date shown, say what we did not check, and never show made-up ratings. Found a mistake? We fix it and log it in our corrections log.