How long does a home battery last? Lifespan and warranty
A battery wears gradually with use and time. Its warranty is the clearest statement of how long the maker expects it to last, as long as you read both of its limits.
In short
Which? says battery systems often come with a 10-year warranty, and that a battery is likely to need replacing during the life of a solar system. Warranties usually cap both the years and the total energy (or cycles) covered. Turn that energy limit into kWh and compare it with how much you will cycle the battery to see which limit you are likely to reach first.
Two limits in one warranty
Most battery warranties promise performance for a number of years or until the battery has put through a stated amount of energy, whichever comes first. Some state that energy in MWh; others as a number of full cycles. Some also promise the battery will keep a stated share of its original capacity by the end of the period. Read all three numbers.
Turning a cycle count into energy
Multiply the usable capacity by the warranted cycles to get the warranted energy in kWh. That ignores the slow fall in capacity as a battery ages, so it is the most generous reading. These worked examples use illustrative figures, not any product's warranty:
| Usable size | Warranted cycles (example) | Warranted energy | Years at one cycle a day |
|---|---|---|---|
| 5 kWh | 6,000 | 30,000 kWh | 16.4 |
| 9.5 kWh | 6,000 | 57,000 kWh | 16.4 |
| 13.5 kWh | 4,000 | 54,000 kWh | 11.0 |
In practice few batteries complete a full cycle every day of the year: in winter a solar-fed battery may barely charge. So for many homes the years limit arrives before the energy limit. A battery charged from the grid every night, on the other hand, cycles daily and may approach the energy limit sooner.
What wears a battery
Capacity falls gradually with the number of cycles and with age. Keeping part of the capacity in reserve, which most batteries do by design, is one of the ways manufacturers manage that. Temperature matters too, which is one reason datasheets state the conditions a battery is designed for and why PAS 63100 cares about ventilation for indoor installations.
A battery doesn't stop suddenly at the end of its warranty. It holds less than it did, and the useful question becomes whether what it still holds suits your evenings.
Solar panels outlast batteries
Which? notes that a battery is likely to need replacing during the life of a solar system. When planning, it is reasonable to think of the panels as the long-lived part and the battery as something you may replace once. That is a point in favour of a connection that would accept a different battery later; ask about it when comparing designs.
Protecting the warranty
- Register the battery with the manufacturer if the warranty requires it, and keep the confirmation.
- Keep the installation paperwork: the electrical certificate, the PAS 63100 statement and the MCS certificate if registered. A warranty claim may ask for proof of a proper installation.
- Ask who stands behind the warranty: the manufacturer, the installer, or both, and what happens if the installer stops trading.
- Note the conditions the warranty sets, such as location, temperature and internet connection for monitoring.
At the end of its life
When a battery is replaced, ask the installer how the old one will be taken away and recycled, and get that in the quote. Removing a battery is electrical work in its own right, and the replacement goes through the same location rules and network notification as the original.
To compare warranties between products, put the figures side by side as comparing specifications suggests. For how usable capacity relates to the label size, see what size battery; for day-to-day care, living with a home battery.
Questions to ask about a warranty
- How many years, and what energy or how many cycles, does it cover? Which limit applies first?
- What share of the original capacity is promised at the end of the period, and how is that measured?
- Does it cover the inverter as well as the battery, and for how long?
- Who handles a claim: the manufacturer, the installer or both? What happens if the installer stops trading?
- Are there conditions, such as an internet connection for monitoring, a temperature range or an annual check?
Put the answers next to each other for each quote. A longer warranty with a low energy limit can cover less in practice than a shorter one with a high limit, and only turning both into kWh makes that visible.
Capacity you can check yourself
Most monitoring apps show the battery's charge in kWh as well as a percentage. Note the full-charge figure soon after installation, then compare it once a year on a mild day. A gradual fall is normal; a sudden drop is worth reporting under the warranty, with the readings to support it.
What this page is based on
- Which? guide to solar panel battery storage (secondary, updated 30 Oct 2026) (read 3 Nov 2026)
- PAS 63100:2024, fire protection for battery energy storage in dwellings (BSI, sponsored by DESNZ), PDF (read 3 Nov 2026)
- MCS Installer Operating Requirements (2026), technologies and use of the MCS mark, PDF (read 2 Nov 2026)
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