How Long Does a Solar Battery Last?Warranties, cycles and the energy floor
How long does a solar battery last? The Energy Saving Trust says about 10 to 12 years, but every warranty ends at the earlier of a term or an energy floor. Here is what Fox ESS, Sigenergy and GoodWe’s own documents say, worked into years.
- The Energy Saving Trust puts a typical home battery’s lifespan at about 10 to 12 years, shorter than a solar panel’s
- Warranties run 10 years (Fox ESS EP, Sigenergy, GoodWe) or 12 (Fox ESS EVO and EQ), each guaranteeing 70% of capacity (60% in one Sigenergy revision) or an energy floor, whichever comes first
- Cycled fully every day, the floor ends the guarantee after about 10.3 years (Fox ESS EP), 8.4 (SigenStor) or 7.0 (GoodWe LX F)
- A battery that only stores your own solar surplus does about 230 cycles a year in our model, so the calendar term is the limit
- Fox ESS lets only the installer claim, and excludes inadequate ventilation and installation by a non-accredited installer
What the Energy Saving Trust says
The Energy Saving Trust puts the typical lifespan of a home battery at about 10 to 12 years, and says it varies with the battery you buy and how you use it. It also says a battery’s lifespan is shorter than a solar panel’s, so you will need to replace the battery before the panels, and tells you to ask about warranties or guarantees for both the battery and its installation. Source: Energy Saving Trust, "Battery storage" (page last updated 6 October 2026).
Three things called “battery life”
The warranty term is a contractual promise, and the number on the brochure. The calendar life is how long the battery keeps working at all. The capacity you keep is how much energy it can still store as it ages. A battery can be inside its warranty and already hold less than when it was new, and a battery can outlast its warranty. The three numbers are different, and the warranty is only a floor under the third.
What a warranty actually guarantees
The warranties for the three brands we fit all have the same shape: the battery keeps at least a stated share of its capacity for a stated number of years or until it has delivered a stated amount of energy, whichever comes first. The share is 70% of nominal energy for Fox ESS, and 70% of usable energy for GoodWe and for Sigenergy’s EU warranty; one 2025 Sigenergy revision says 60%.
| Battery | Term | Capacity kept | Energy floor, as full cycles |
|---|---|---|---|
| Fox ESS EP5 / EP11 | 10 years | 70% of nominal energy | about 3,750 (EP5: 19.42 MWh on 5.18 kWh; EP11: 38.85 MWh on 10.36 kWh) |
| Fox ESS EVO / EQ | 12 years | 70% of nominal energy | EVO about 4,680 (EVO10: 47.88 MWh on 10.24 kWh); EQ about 3,750 (EQ4800: 17.47 MWh on 4.66 kWh) |
| SigenStor BAT 5.0 / 8.0 | 10 years; extension to 15 | 70% of usable energy (EU warranty); 60% in one 2025 revision | about 3,050 (BAT 5.0: 15.85 MWh; BAT 8.0: 23.77 MWh) |
| GoodWe Lynx Home F | 10 years performance; 5 years product (global document) | 70% of usable energy | about 2,560 (LX F 9.8-H: 25.16 MWh on 9.83 kWh) |
Full cycles = the energy floor ÷ the battery’s stated energy (nominal for Fox ESS, usable for Sigenergy and GoodWe); that division is our arithmetic, not a manufacturer claim. Sigenergy’s figures come from extracts of its EU warranty rather than the PDF itself, so check the current document. Sources: Fox ESS Battery Warranty Policy, UK & Ireland (V4.4); Sigenergy SigenStor warranty (EU); GoodWe Lynx Home F PLUS+ product page; GoodWe, warranty extension for hybrid inverters in 2026.
When does the energy floor actually bite?
It depends on how hard you work the battery. One that only soaks up your own solar surplus does far fewer full cycles a year than one charged every night on a cheap tariff, so for the first the calendar term is the limit, and for the second the energy floor can be:
| How you use it | Fox ESS EP | SigenStor | GoodWe LX F |
|---|---|---|---|
| Soaking up your own solar surplus (model: 4 kW array, 5 kWh battery, medium home) — about 230 cycles a year | 16.3 years | 13.3 years | 11.1 years |
| One full cycle every day, the heaviest realistic use — 365 cycles a year | 10.3 years | 8.4 years | 7.0 years |
Years until the energy floor = floor in full cycles ÷ cycles a year. Solar-only cycles come from our monthly model (PVGIS yields, bright and dull days, 90% round-trip efficiency, energy put into the battery ÷ its usable size). Where the floor comes later than the 10-year term, the term ends the guarantee first.
So for a home that only stores its own surplus, the number of years on the brochure is the number that matters, on any of the three. For a home that cycles the battery every day — on a cheap-rate smart tariff, say — GoodWe’s floor arrives after about 7 years and Sigenergy’s after about 8, while Fox ESS’s EP floor lands just beyond its 10-year term.
What can end a warranty early
The conditions sit in the small print. Fox ESS’s policy makes its performance guarantee conditional on the ambient temperature staying between −10°C and 50°C and on energy throughput staying under the table above. It excludes claims caused by inadequate ventilation, improper installation or installation by a non-accredited installer, and lists a clearance of at least 300 mm around the battery pack for cooling among its conditions. Sigenergy’s datasheet gives an operating range of −20 to 55°C. The Energy Saving Trust adds that a system should never let a battery discharge to zero, because that can significantly reduce its life. Sources: Fox ESS Battery Warranty Policy, UK & Ireland (V4.4); Sigen Battery datasheet; Energy Saving Trust, "Battery storage" (page last updated 6 October 2026).
Separately, BS 7671:2018+A4:2026 requires batteries in dwellings to be installed in line with PAS 63100, which keeps them out of rooms where people sleep, unprotected escape routes and lofts. None of this is exotic, but it is why where and how the battery is installed matters as much as which brand it is.
Who makes the warranty claim?
Fox ESS’s policy says the only people eligible to claim under it are the installer and Fox ESS authorised personnel. If the installer has gone into administration or insolvency, or the site is remote, the end user or installer may, at their own discretion and expense, appoint a local installer to carry out the installer’s functions. So the warranty is a promise from the manufacturer that you reach through the person who installed the battery — a reason to choose an installer who will still be there in year eight.
Will it repay itself before it wears out?
That is the better question. In our model a 5 kWh battery on a 4 kW solar home adds about £133 a year on a flat 26.32p tariff. At Octopus’s published battery-only price of £3,947 that is a payback of roughly 30 years — longer than the 10 to 12 years the Energy Saving Trust gives for a battery’s life. A cheap-rate tariff changes the sums, which is why our battery storage installation page works through both cases with published prices before it recommends anything.
Frequently Asked Questions
How long does a solar battery last?
The Energy Saving Trust gives a typical lifespan of about 10 to 12 years. Manufacturer warranties run 10 years for Fox ESS EP, GoodWe and Sigenergy and 12 years for Fox ESS EVO and EQ.
Is a 10-year battery warranty 10 years of full capacity?
No. It guarantees that the battery keeps at least a stated share of its capacity — 70% for Fox ESS and GoodWe, 60–70% for Sigenergy — for the term or until an energy floor, whichever comes first.
What is the energy throughput floor?
The amount of energy a battery must have delivered before the warranty stops covering capacity loss. Divided by the battery’s stated energy it gives full cycles: about 3,750 for a Fox ESS EP, 3,050 for a SigenStor and 2,560 for a GoodWe LX F.
Will I need to replace my battery before my solar panels?
Probably. The Energy Saving Trust says a battery’s lifespan is shorter than solar panels’, so you will need to replace the battery before the panels.
What happens when a battery warranty ends?
The guarantee on retained capacity ends. The Energy Saving Trust gives a typical lifespan of about 10 to 12 years, so plan for a replacement at some point after year ten.
Who claims on a home battery warranty?
For Fox ESS, the installer. Its UK and Ireland policy says only the installer and Fox ESS authorised personnel can claim, and lets the end user or installer appoint a local installer, at their expense, if the original installer has become insolvent.
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