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BatteriesHow to read a battery warranty before you sign anything
A battery warranty is four promises in one document: a term, a capacity floor, a usage limit and a page of conditions. Read only the number of years and you have read almost none of it.
Updated 4 August 2026 · from the OVO Solar & Battery team
A warranty is a promise about capacity, not breakdown
A battery warranty is mostly a promise about capacity, not about breakdown. It says that after a set number of years, and within a set amount of use, the battery will still hold at least a stated percentage of the capacity it had on day one. That percentage is the retained capacity figure, and it is the number to compare first. The years on the front page mean very little without it.
Retained capacity, in real numbers
A 13.5 kWh usable battery warranted to 80% at 10 years must still give you at least 10.8 kWh in year 10. That floor is the worst case the manufacturer will stand behind, not a forecast. Most batteries sit comfortably above it, and none of them stop working on the last day of the term.
The four numbers, and the conditions underneath them
| What it is | What it promises | Where it catches people out |
|---|---|---|
| The term | How many years the manufacturer will stand behind the battery, usually 10 to 15 in the UK market | The term normally starts at commissioning rather than on the day you paid |
| Retained capacity | The minimum share of original usable capacity left at the end of the term, commonly 70% to 80% | Two warranties with the same term can guarantee very different amounts of capacity |
| Cycle limit | A cap on how many full charge and discharge cycles are covered, often around 6,000 where one applies | Some products state unlimited cycles for ordinary household use, which is a materially stronger promise |
| Throughput limit | A cap on the total energy pushed through the battery across its life, quoted in kWh or MWh | This is the limit that bites on a battery worked hard every day, and the one most people never reach in the document |
| Conditions | What you have to do to keep the cover, such as keeping the system connected so it can take firmware updates | Conditions sit at the back, in the shortest type, and they are enforceable |
Warranty structures vary by manufacturer and by country, and the same product can carry different terms in different markets. The version that counts is the document supplied with your own quote.
Why the cycle limit rarely bites first
One full charge and discharge a day is a hard working home battery. At that rate a 6,000 cycle allowance is over 16 years of use, which is longer than any headline term in the mainstream UK market. Warranties that quote both a term and a cycle count almost always add whichever comes first, so the clock and the counter run together and the first to expire ends the cover. For most households the years run out well before the cycles do, which is why the term and the capacity floor deserve more of your attention than the cycle number.
Throughput is the clause to read
Throughput is the total energy the manufacturer will cover over the life of the battery. Some warranties introduce one as soon as the battery is doing more than ordinary self consumption, time of use and backup, and heavy overnight grid charging is exactly that. The arithmetic is quick. A 10 kWh battery cycled fully every day moves about 3,650 kWh a year, so roughly 36,500 kWh over 10 years. Divide any throughput figure in the document by your own annual number and you will see immediately which limit lands first.
What the UK market actually publishes
| Product | Headline warranty | What the document adds |
|---|---|---|
| Tesla Powerwall 3 | 10 years, 80% of original capacity retained in the UK | Unlimited cycles for self consumption, time of use and backup, and a reliable internet connection is required so the unit can take firmware updates. The 70% floor sometimes quoted online applies to a small group of other European countries, not to the UK. |
| Enphase IQ Battery 5P | 15 years or 6,000 cycles, whichever comes first | The longest headline term in the mainstream UK market, and a clear example of a warranty where the cycle counter can end the cover before the years do. |
| Fox ESS EQ range | 12 years on the stackable EQ modules | Modules are specified to 90% depth of discharge and rated IP65, so the usable figure is 90% of the nominal capacity on the datasheet. Compare usable to usable. |
| Sunsynk ECCO | 5 years on the hybrid inverter as standard | The 5.32 kWh module is rated for up to 6,000 cycles, which is a design rating rather than a warranty promise. Ask for the battery warranty separately from the inverter warranty. |
Manufacturer figures as published and checked on 3 August 2026, and subject to change. These are market examples chosen to show how differently the promises are built, not a list of what OVO fits. Where a manufacturer does not publish a retained capacity figure we have not guessed one, so ask for the warranty document itself. Your quote names the exact product and its terms.
Two things fall out of that. The terms on the battery itself run from 10 to 15 years, and the shape of the promise varies far more than the length of it, so compare the floor and the limits before the headline. The inverter is also often warranted separately, and for less time than the cells it serves, so one number rarely covers the whole system. Sizing changes the arithmetic as well, and what size battery do I need works that through. Kit pricing sits on the costs page.
Ask for the actual warranty document on your free 45 minute video design, alongside the written quote you get on the call.
Get your free quote →A warranty is only as good as the company behind it
This stopped being theoretical in April 2026. GivEnergy, at one point the best known domestic battery brand in the country, was offering 12 years with unlimited cycles and a 70% retention guarantee on systems installed from September 2023. On paper that was one of the stronger promises on the market. The company entered administration on 9 April 2026, ceased trading and made its staff redundant, with unsecured creditors owed more than £17 million and no buyer confirmed when the administrator's proposals were filed in late May 2026.
Installed hardware carried on working. A home battery does not need the manufacturer's servers to charge from your roof or carry your evening, so those systems kept running. What did not survive was the ability to claim against that manufacturer, along with cloud features and future firmware updates. The UK Energy Storage Association issued guidance and owners were pointed back to the business that installed the system. The lesson is not to be frightened of one brand. It is that a paper promise needs somebody solvent still standing behind it in year 12, so who sells and fits your system counts for as much as the number printed on the datasheet.
The layer no product warranty covers
Manufacturer warranties cover the equipment. They do not cover how it was fitted, and in the first decade a solar and battery system is more likely to give trouble because of the installation than because a cell failed. Every OVO installation carries the OVO guaranteed 10 year workmanship warranty, and it is backed by OVO rather than by the individual business that arrives at your house. The work is carried out by the regional partner holding the exclusive OVO partnership for your area. Sixteen installer businesses are Powered by OVO, selected from around 200 assessed, and between them they completed over 1,000 OVO solar and battery installs in the last 12 months. Put your postcode into the coverage page to see who covers you.
How to compare two quotes in five minutes
- Find the retained capacity floor on both, then compare that before you compare the years. A 10 year term holding 80% is a stronger promise than a longer one guaranteeing less.
- Check which limits apply: years only, years or cycles, years or throughput, or all three with whichever comes first.
- Work out your own annual throughput from the capacity you would cycle each day, and see whether either quote's cap is anywhere near it.
- Read the conditions page. Look for anything about internet connection, commissioning, registration deadlines and who is allowed to work on the system.
- Get the workmanship warranty in writing as a separate document, because it covers the failures a product warranty never reaches.
Book the free 45 minute video design and your local OVO expert will go through the kit, the warranty terms and a written quote on the call, with nobody visiting your home.
Get your free quote →Warranty questions, answered
What does 80% retained capacity actually mean?
It is a floor, not a prediction. It means the manufacturer guarantees the battery will still hold at least 80% of its original usable capacity at the end of the term. On a 13.5 kWh usable battery that is 10.8 kWh in year 10. Real batteries usually sit above the floor, and they keep working after the term ends, just with slightly less capacity than they started with.
Is a 15 year warranty better than a 10 year one?
Not automatically. A longer term with a lower capacity floor, a cycle cap and a throughput cap can be a weaker promise than a shorter term with a high floor and unlimited cycles for normal household use. Compare the floor, then the limits, then the length. If two documents are genuinely close, the length decides it.
What happens to my warranty if the manufacturer goes out of business?
The product warranty goes with them. GivEnergy's collapse in April 2026 showed how that plays out: the hardware kept charging and discharging because it does not depend on the manufacturer's servers, but claims against the company did not survive and owners were directed back to their installer. It is the clearest argument there is for buying through a business with the scale to still be answering the phone in a decade.
Does charging from the grid overnight affect my warranty?
It can, and it is worth checking before you build a strategy around it. Some warranties cover unlimited cycles for self consumption, time of use and backup but apply an energy throughput limit once the battery is used for anything beyond that. Daily off peak charging pushes a lot of energy through the pack, so find the throughput clause and do the arithmetic against your own usage rather than assuming unlimited means unlimited.
Does the battery need to stay connected to the internet?
For some products, yes. Tesla's warranty requires a reliable internet connection so the Powerwall can receive firmware updates, and connection conditions of that kind appear across the market on both storage and solar equipment. It is rarely a problem in practice, but it is a condition, and conditions are the part of a warranty that gets enforced.
What is the difference between the product warranty and the workmanship warranty?
The product warranty is the manufacturer's promise about the equipment: defects, failures and how much capacity is left at the end of the term. The workmanship warranty covers the installation itself, which is the layer no manufacturer will touch. Every OVO installation carries the OVO guaranteed 10 year workmanship warranty, backed by OVO rather than by the regional partner who fits the system.
Will my battery still be worth using after the warranty runs out?
Almost certainly. Cells fade gradually rather than failing on a set date, and at one full cycle a day a 6,000 cycle rating is more than 16 years of use, so the time limit usually arrives long before the cells are worn out. Expect a well specified battery to carry on doing useful work past its term with a little less capacity than it had on day one.
Figures and specifications in this guide are sourced below and were checked on the date shown. Rates and product specifications change; we confirm the current picture on your free design call.
Sources
- Tesla Powerwall limited warranty for EMEA, term, capacity retention by country and cycle conditions energylibrary.tesla.com
- Enphase IQ Battery 5P warranty term and cycle limit switchtogether.co.uk
- Fox ESS EQ battery range specifications, depth of discharge and 12 year warranty, manufacturer UK site fox-ess.uk
- Sunsynk ECCO hybrid inverter range and standard inverter warranty term sunsynk.org
- Sunsynk 5.32 kWh module cycle rating and depth of discharge powerland.co.uk
- GivEnergy enters administration, 9 April 2026, cessation of trading and creditor position ess-news.com
- UK Energy Storage Association guidance for GivEnergy owners esa-uk.org
- What administration meant for existing GivEnergy owners, hardware operation and warranty position spiritenergy.co.uk
- GivEnergy legacy 12 year warranty terms for systems installed from September 2023 ukgei.co.uk
- Administrator's Statement of Proposals position, no buyer confirmed as at late May 2026 solar-tech-support.co.uk
- OVO guaranteed 10 year workmanship warranty, Powered by OVO partner network and installed volumes ovosolarandbattery.co.uk
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