Guide · Batteries
How long do solar batteries last?
Checked by our MCS-certified installers · Updated October 2026
Short answer
Every battery we fit comes with a 10-year warranty, and it keeps powering your home long after that.
Fox ESS, Sigenergy and Tesla Powerwall 3 each guarantee how much your battery holds at year 10. The Fox ESS EP12's warranty covers about 3,750 full charges — one a day for ten years. Fitted from £1,990.
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What each warranty promises at 10 years
From each maker's warranty: Fox ESS (UK battery warranty, September 2025), Sigenergy (Europe, May 2025) and Tesla (European region incl. the UK, December 2025). The warranty ends at 10 years or at the energy limit, whichever comes first. Your quote lists the warranty of every part.
Nominal, usable, rated: why 70%, 80% and 60% aren't the same thing
- Nominal
- Everything the cells can hold. A Fox ESS EP12 is 11.52 kWh.
- Usable
- What the battery lets you use. It keeps a reserve so the cells are never run flat — about 10.4 kWh on an EP12.
- Rated
- The capacity a battery is sold as. Tesla Powerwall 3 is 13.5 kWh.
- State of health
- How much it holds today compared with new, as a percentage. New is 100%.
Each maker measures its promise from a different starting point, so compare like with like. 70% of an EP12's nominal 11.52 kWh is about 8 kWh still in the battery at year 10 — the minimum Fox guarantees.
What wears a battery
- Heat — a battery in a hot spot ages faster
- Hard frost, for models not rated for outdoors
- Being run completely flat over and over
- Charge cycles — each full charge and use is one
How we make it last
- A cool, ventilated spot chosen at the survey
- The battery's own software stops it running flat
- Warranty registered in your name on the day
- Firmware updates arrive through the app
Battery life questions
What is battery state of health?
It is how much energy the battery holds today compared with when it was new, shown as a percentage. A new battery is 100%, and the maker's warranty guarantees a set level for 10 years.
What is the difference between nominal and usable capacity?
Nominal is everything the cells can hold. Usable is what the battery lets you use — it keeps a reserve so the cells are never run completely flat. A Fox ESS EP12 is 11.52 kWh nominal and about 10.4 kWh usable.
How many charge cycles does a home battery last?
Makers set an energy limit rather than a cycle count. The Fox ESS EP12's warranty covers 43.19 MWh — about 3,750 full charges, or one a day for ten years. Tesla sets no limit for normal home use.
Is 70% after 10 years good?
It is the minimum the maker guarantees, not a prediction. An EP12 at 70% of its nominal capacity still holds about 8 kWh. Compare warranties on the same basis: 70% of nominal, 80% of rated and 60% of usable are measured from different starting points.
What happens when the warranty ends?
It keeps working and powering your home. With a modular battery you can also add a module later for more storage.
Do home batteries need servicing?
No routine servicing. Keep the area around it clear and the app connected so it gets its updates.
Is the inverter covered by the same warranty?
Usually it has its own warranty. Your quote lists each part's warranty separately.
Does the warranty move with the house if I sell?
It depends on the maker's terms — we tell you for the battery you choose.
Get started
A battery chosen to last.
A free survey picks the right battery and the right spot for it, with a fixed price — usually within 24 hours.
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