A home battery warranty is rarely a single number. Most terms combine three limits — a period in years, a total energy throughput, and a minimum retained capacity — and cover ends when the first of them is reached, not the last. Quoting only the headline "10 years" to a customer hides the other two. This guide shows installers and distributors how to read the three limits together, what conditions and exclusions typically sit behind them, and what to keep in writing before an order is placed.
The three limits behind a home battery warranty
A warranty document usually states three separate limits, and they act as a chain: the weakest one governs.
| Limit | What it states | Unit | Why it decides the outcome |
|---|---|---|---|
| Term | How long cover lasts from its start date | years | Sets the outer boundary |
| Throughput | The total energy the pack may pass before cover ends | MWh, or equivalent full cycles | A hard-cycling household can reach it years before the term |
| Capacity retention floor | The minimum share of original capacity the pack must still hold | % of nameplate | This is the actual performance promise at the end of cover |
Whichever limit is reached first ends the warranty. A pack with a 10-year term and a 10 MWh throughput cap can be out of cover in year six if the load cycles it hard; a lightly cycled pack could take longer to reach the same throughput but be stopped by the term. Ask for all three, in the same document, for the exact SKU.
Why the cycle figure on the datasheet is not the warranty
Datasheet cycle life and warranty length are different promises. A figure such as 6,000 cycles at 80% depth of discharge at 25 °C is a specification measured under stated conditions — the condition is part of the number. Battery University's guide to prolonging lithium-based batteries sets out how capacity fade depends on temperature, depth of discharge and the charge level a pack is held at, which is exactly why a cycle figure needs its test conditions and why a warranty states its own throughput and capacity limits rather than inheriting the datasheet number.
Two consequences for a quote:
- A datasheet cycle count is not a warranty duration, and a published design life is not a warranty duration either.
- A warranty that promises a term but no throughput or capacity floor tells you very little about how the pack should perform at the end of that term.
Our datasheet guide covers which conditions to look for, and cycle life explained translates cycles into years of service.
What cover usually excludes, and the conditions that keep it valid
Exclusions vary by supplier, but the categories are consistent enough to read line by line. Treat the list below as the things to look for in any battery warranty, not as a statement of one supplier's terms:
- Installation not to the manual — incorrect mounting, cabling or inverter settings.
- Damage, water ingress or use outside the stated ambient window.
- Unauthorised repair, modified firmware or non-approved accessories.
- A missing commissioning record, or a system commissioned without one.
- Duty-cycle mismatch — a residential unit worked beyond its rating.
- Normal capacity fade down to the stated floor, which is expected performance rather than a fault.
Alongside the exclusions, look for the conditions that must stay true for cover to continue: registration of the product or its serial number, the original invoice, professional installation, and firmware kept within supported versions. These are the clauses that decide most real claims.
Manufacturer warranty and statutory rights are not the same thing
A manufacturer's commercial warranty is a contractual promise from the supplier. It sits alongside — and does not replace — the statutory rights a buyer has against the seller in their own market, and those rights have their own remedies and time limits. In the EU, stationary battery energy storage systems are also addressed by the Batteries Regulation (EU) 2023/1542, which covers state-of-health and expected-lifetime data in the battery management system (EUR-Lex, Regulation (EU) 2023/1542); confirm the exact scope and application dates for your SKU and market rather than assuming. For a distributor or installer, the practical point is that the customer's route to remedy and the manufacturer's warranty route can be different paths.
How to compare two warranties fairly
Headline terms are not comparable until they are normalised to the same basis.
| Step | What to do | Why |
|---|---|---|
| 1. Same term basis | Measure both from the same start point (commissioning or invoice date) | A term counted from the invoice is longer in service than one counted from manufacture |
| 2. Convert throughput | Divide the throughput cap by usable capacity to get equivalent full cycles | Makes an MWh cap comparable with a cycle count |
| 3. Read the capacity floor | Express it as a percentage of nameplate | It is the real end-of-cover performance promise |
| 4. Identify who honours it | Manufacturer, importer or distributor? | A claim is only as strong as the party behind it |
| 5. Check parts, labour and shipping | Is replacement labour covered, and for how many years? | Parts-only cover can still leave the customer out of pocket |
| 6. Check transferability | Does cover follow the product if the home is sold? | Transferred cover is easier for the buyer to value |
Worked illustration (assumption visible, not a specification): a 10.24 kWh module at an 80% usable share gives about 8.2 kWh usable. A 10 MWh throughput cap is therefore roughly 1,220 equivalent full cycles. Compare that with the term and with the household's expected cycling before telling a customer the cover "lasts ten years" — the throughput figure may end it first.
What to get in writing before you quote
- The full warranty document for the exact SKU, not a marketing summary of it.
- All three limits — term, throughput and capacity floor — and the date each is counted from.
- The party that honours the warranty, and the claim route to use.
- Exclusions and the conditions that must stay true for cover to continue.
- What is included in labour, parts and shipping on a claim.
- How a claim is evidenced — a state-of-health report, a field test, or logged data.
We provide the current terms for the exact SKU in writing, alongside the datasheet, rather than a headline number in a brochure — ask for the document and we will send it. The UL 1973 listing guide covers the certification side of the same question, and how installers evaluate a supplier puts warranty support in the wider procurement picture.
What to record at commissioning so a claim stays valid
Most claims turn on what was documented at handover. Capture, on the day:
- Date, installer and site, with serial numbers for every module.
- Firmware and software versions.
- The reserve and cut-off settings as commissioned, and the circuits on the backup output — the scope of which is set out in our backup-scope guide.
- The measured ambient at the install position.
- The original invoice, and the customer's stated expectations, in writing.
If the system may grow, plan the record so it still matches the installed configuration after the first expansion — the same discipline that expansion planning asks for. And confirm the inverter pairing is on the verified list before you rely on any performance figure at all, per our inverter compatibility guidance.
Tell us the SKU and the market
Send us the exact product, the destination market and the inverter if it is already fixed. We will return the datasheet, the current written warranty terms for that SKU, and a note on what has to be documented at commissioning so a claim is not contested on a technicality. If you are still comparing configurations, start from the site and the load list and we will work forward from there.
Tell us about the project, or browse the full storage range and the Storage Wall series.