Home Battery Warranties: Retained Capacity, Throughput and Conditions

A home battery warranty is normally two promises in one document. The product warranty covers defects in materials and workmanship; the performance warranty covers output, in this case retained storage capacity, over time¹. Most UK-sold home batteries carry a ten-year term, and the longest mainstream terms run to fifteen years. Which nails down when the cover really ends: it is usually whichever of three limits arrives first, the years, a cycle count or a total energy throughput.

The benchmarks to hold in mind are these. Battery systems often come with a ten-year warranty², and most quality batteries carry at least a ten-year manufacturer warranty³. Around 70 per cent retained capacity after ten years is the common guarantee, with the industry spread running from 60 to 80 per cent of original nominal energy⁴. The Enphase IQ Battery 5P and the IQ Battery 5P with FlexPhase are covered for fifteen years up to 6,000 cycles, ending on the earlier of fifteen years from the activation date or 6,000 discharged cycles⁵.

The conditions matter as much as the headline. Registration windows, continuous internet connectivity, installation by a qualified installer, siting away from temperature extremes and short defect-reporting deadlines all appear as terms that can cut a warranty short. Separately, and independently of any manufacturer promise, statutory consumer rights in England and Wales expire six years from delivery of the goods, and in Scotland five years⁵.

What the warranty actually covers: product and performance

The split is standard across solar and storage. A product warranty covers defects in materials and workmanship, while a performance warranty covers output over time¹. For a battery, the myenergi libbi warranty puts the product side plainly: it covers manufacturing defects and component failures under normal use, provided the system is installed and operated as specified¹⁰.

The performance half is narrower than buyers often assume. In the Solarwatt documentation the performance warranty applies only to the battery module and not to other components of the product or any AC sensor¹¹. So the cell stack may carry a decade of retained-capacity cover while the inverter, controller, gateway or sensors sit on shorter terms in the same document. Enphase runs exactly that structure: fifteen years on the IQ Battery 5P with FlexPhase, ten years from the activation date on the IQ System Controller, and five years from the activation date on the system shutdown switch, IQ Gateway, Mobile Connect, consumption CT and communications kit⁵.

Exclusions are worth reading as carefully as the term. The SolaX residential battery warranty does not include any accessories and tool kit items provided with the product⁴. The GivEnergy single-phase battery warranty excludes any maintenance works conducted or arranged by the buyer, giving cleaning of the battery pack as an example¹².

Two further layers sit outside the battery box. Workmanship, meaning the quality of the installation itself, is a separate promise: an OFTEC-style workmanship warranty is fully transferable between owners of a property¹³. Installed equipment sold alongside a battery may carry its own shorter terms, for example the 3-year product and 1-year workmanship warranty quoted on E.ON Next home EV chargers.

For a household, the practical test when comparing documents is which components are named, what the retained capacity figure is, and what ends the cover first. Capacity, depth of discharge rating, warranty and expected lifetime are the selection factors a buyer is pointed at¹⁴.

Length: ten years is the norm, fifteen the outer edge

Ten years is the anchor. Battery systems often come with a ten-year warranty², warranties typically cover batteries for ten years or a certain number of cycles¹⁵, and most quality batteries come with at least a ten-year manufacturer warranty³. Electric home batteries carry warranties generally covering ten years¹⁶. Product-level examples match: Powervault states a ten-year warranty on its home batteries¹⁷, the SolarEdge Home Battery is listed at ten years¹⁸, SunPower Home Energy Storage at a ten-year warranty on product and performance¹, and the myenergi libbi battery modules at ten years from the date of installation or commissioning¹⁰.

Above that sit fifteen-year terms. The Enphase IQ Battery 5P and the 5P with FlexPhase are both stated at fifteen years up to 6,000 cycles⁶. Longer terms also appear in official material: an Ofgem ECO4 approved innovation measure describes an unreplaceable battery with a twelve-year manufacturer's warranty²⁰.

The term should be read against expected life rather than treated as a lifespan claim. The Energy Saving Trust puts the typical lifespan of a home battery at about ten to twelve years⁷; Home Energy Scotland says batteries tend to last between ten and fifteen years⁸. Those two independent figures overlap but are not identical, and both are estimates rather than guarantees. A ten-year warranty therefore covers roughly the period in which a battery would be expected to be working anyway, which is the point: the warranty is protection against early failure and faster-than-modelled fade, not a promise of a fixed service life.

Warranty length on car batteries is written differently again and is not a good guide: EV battery warranties run at least eight years or 100,000 miles²¹, with most manufacturers offering seven or eight years²² and some five to eight²³. Home storage is not mileage-limited, so the limiting factor is cycles or throughput instead.

Retained capacity: the 70% after ten years benchmark

Most manufacturers guarantee around 70 per cent capacity after ten years⁴, and one maker's guidance describes that figure as guaranteeing at least 70 per cent capacity after ten years of intensive daily cycling²⁴. The wider industry spread is 60 to 80 per cent of original nominal energy, with 70 per cent the common standard⁴. End-of-life capacity thresholds in warranty documents cluster at 60, 70 or 80 per cent²⁵.

The variation across real documents is large enough to matter:

Note the conditions attached to the highest figure. The 80 per cent Rayleigh promise applies to systems operating under self-consumption mode with an internet connection, and its 120 months runs from the earlier of installation at the end user's property or two months after sale to another business²⁶. A high headline number with narrow qualifying conditions is not necessarily stronger than a lower number with none.

Falling below the threshold does not stop a battery working, it means less stored energy each cycle. By comparison, for EV cells the maker guidance is that once capacity falls below 80 per cent drivers may start to notice a fall in range and performance²³. Household systems also hold back capacity by design: when the battery gets down to a set level, maybe 20 per cent of the total storage capacity, the system will stop discharging⁷. That reserve is a control setting, not degradation, but it affects what a household actually gets out of a pack. The mechanics of fade are covered in more detail under battery cycle life and degradation and usable capacity.

Throughput and cycles: the limit that can end cover early

A warranty period is often defined not only by time but by usage limits such as the number of cycles or total throughput energy²⁸. Many battery warranties end when the system reaches its throughput limit, even if the time period has not expired²⁵, and the warranty usually ends when either the cycle limit or the time limit is reached, whichever comes first⁴. Tesla's Powerwall 2 battery modules are listed at ten years or energy throughput, whichever comes first, with the remedy being replacement or payment of current market price²⁷.

The two ways of writing the usage limit behave differently. Cycle counting is the older method: many manufacturers advertise warranties based on a fixed number of charge and discharge cycles, such as 10,000 cycles over ten years²⁹. The risk is in the definition.

Multiple cycles can therefore accumulate within a few hours, meaning the cycle limit may be reached much sooner than expected³⁰. That matters most to households on time-of-use tariffs, where a battery may charge and discharge in short bursts several times a day. Enphase sets its limit at 6,000 discharged cycles across fifteen years⁵; electric home batteries generally are described as having a limited cycle life of 3,000 to 5,000 cycles¹⁶.

Throughput sidesteps the definition problem. Battery throughput is the total amount of energy a battery can charge and discharge over its entire lifetime, usually measured in kWh or MWh²⁵. SunPower guarantees a total energy throughput in MWh determined by the storage capacity of the battery system, instead of a maximum number of charge and discharge cycles³⁰, across a ten-year period, with the allowance varying according to storage capacity³¹. Throughput energy is described as offering a precise evaluation of how much energy a battery can deliver before reaching the end of its effective life, incorporating depth of discharge²⁸.

Throughput limits can also be imposed as a penalty for operating outside the maker's control system. If a myenergi libbi battery pack is connected to a third-party system or manually operated outside the myenergi Controller, the warranty expires when a maximum of 3MWh per kWh of usable capacity has been reached, and five years applies to the hybrid inverter and controller³². That is a direct trade between third-party control and warranty length, and it bears on any plan to use a battery with grid services or a virtual power plant.

Conditions that can void the warranty

Voiding conditions cluster around installation, siting, connectivity and who touches the equipment afterwards.

• Self-installation. Attempting a DIY installation with high-voltage DC runs carries extreme risk and will instantly void product warranties²⁴. See DIY home battery builds.
• Siting. Installing a battery in uninsulated areas that experience ambient temperature extremes can void coverage²⁴. Ventilation and temperature limits are set out separately.
• Moving the unit. Moving the battery after its first installation, even to the same address, voids the SolaX warranty unless a qualified installer re-tests it⁴.
• Unauthorised parts. Replacing the battery or accessories without prior consent from SolaX can void the claim⁴.
• Self-arranged repair. Under the myenergi product warranty, if you arrange your own installer to conduct any repair, the warranty will be void³³.
• Regulatory compliance. GivEnergy requires that installation, use and maintenance comply with all applicable laws, regulations, safety standards and the product and installation manuals¹².
• Connectivity. Enphase requires that covered products be continuously connected to the internet during the limited warranty period, except where interrupted by causes outside the owner's reasonable control⁵.
• Bespoke additions. Connecting a wind turbine to an existing battery using a bespoke arrangement carries the expensive risk of invalidating warranties for the battery, inverter and possibly the turbine³⁴.

Registration deadlines are the quiet trap. Failing to register a warranty with the manufacturer within thirty days of installation is listed by Which? among common mistakes that invalidate boiler warranties³⁵, and the same discipline applies to storage. With SolaX, if the system was not registered within ninety days, the warranty automatically starts six months after the battery left the factory, which can silently remove months of cover⁴. Activation deadlines go further still: the Enphase warranty does not cover IQ Batteries activated after the "Energize by" date printed on the battery or packaging⁵. Stock that sits in a warehouse too long can therefore arrive uncovered.

Usage rules can also apply to portable products. Jackery's warranty does not apply to the battery cell unless the cell is fully charged within seven days after purchase and at least once every six months thereafter³⁶.

Start dates, registration and the activation clock

The warranty clock rarely starts on the day a household signs a contract. Four patterns appear:

The practical consequence of a production-linked start is that a battery bought from older stock begins its warranty behind schedule. The Rayleigh RI-ENERGYSET 120-month term runs from the earlier of installation at the end user's property or two months after sale to another business or personnel²⁶, which again favours fast-moving stock. Where a start date depends on registration, the registration is normally the installer's job, and evidence that it was done belongs with the handover paperwork described under the installation process.

Enphase: fifteen years on the IQ Battery 5P, with strict deadlines

The Enphase storage warranty effective on or after 15 September 2025 is one of the longest and one of the most conditional documents in the UK market. Its covered territory is Scotland, England and Wales, and it is governed by and construed in accordance with the laws of England⁵. Northern Ireland is not named in that territory statement.

The hardware itself is an all-in-one, AC-coupled storage system with a total usable energy capacity of 5.0 kWh, usable in single-phase and three-phase installations¹⁹. AC coupling is explained under AC and DC coupled systems, and the product in detail on the Enphase IQ Battery 5P page.

One exclusion deserves emphasis for anyone planning around medical need:

The connectivity requirement is the term with the widest reach. A fifteen-year promise conditional on permanent internet connection ties the household to a working router, a maker's cloud and a maker's account for the whole period. That is a real dependency, discussed further under monitoring a home battery.

Inverter warranties and extensions: Solplanet

Battery warranties usually sit beside a separate inverter warranty, and inverters are frequently the shorter of the two. Solplanet offers end-users a standard warranty of up to five years, and states that the warranty can also be extended for up to ten years³⁷. The document does not resolve how the five-year and ten-year figures relate, so both are given as published.

Solplanet also states that its terms are offered "without affecting the legal warranty provided by any wholesaler or retailer"³⁷, which is the correct position: a manufacturer's promise is additional to, not a substitute for, the rights a buyer holds against the seller. On claims handling, the maker says that if necessary its logistics network will deliver a replacement inverter directly to the end user, and that problems should be raised with its customer support department or through the online claim form³⁷.

Sungrow's marketing material speaks to system benefits rather than warranty structure, describing reduced waste from a home solar power system and a house guarded from potentially dangerous power outages. Those are maker claims about products, not warranty terms, and the specific extension arrangements for Sungrow inverters are not set out here. The Sungrow home batteries page covers that range.

The general point for a household is that a system's weakest warranty sets the practical exposure. A ten-year battery module behind a five-year inverter means the electronics may need replacing at the household's cost while the cells are still covered.

Warranties and statutory consumer rights

A manufacturer warranty is a voluntary extra. Statutory rights run against the seller and have their own clock: for goods purchased in England and Wales these rights expire six years from delivery of the goods, and in Scotland five years from delivery⁵. Those periods are shorter than a ten or fifteen-year warranty, so for older faults the manufacturer document is often the only live route; for early faults a household may have both.

Making a warranty claim is a contractual process: Citizens Advice describes needing details of what the problem is when claiming under a warranty or guarantee³⁸. Manufacturers add their own evidence requirements, for example myenergi asking for proof of purchase of the product and its serial numbers³².

Installation work is governed separately again. Workmanship warranties cover the quality of the installation and are fully transferable between owners, passing automatically to a new owner if the home is sold, for the duration of the warranty period¹³. Consumer-protection schemes listed by RECC add backstops: Home Improvement Protection offers cover up to ten years and up to £50,000, with a thirty-day defect reporting limit, and Homepro is listed at ten years with a £100 figure and a thirty-day reporting limit³⁹. Those schemes matter most when the installer, rather than the manufacturer, has stopped trading.

Where a dispute concerns an energy supplier rather than a product, the Energy Ombudsman route requires complaining to the supplier first, waiting eight weeks or receiving a deadlock letter, holding sufficient evidence including the date the complaint was raised, and confirming the supplier name matches the bill⁴⁰.

Making a claim: deadlines, RMA numbers and replacements

Claims fail on timing more often than on substance.

1. Report the fault immediately. BYD requires notification of the defect or deterioration within thirty days of the original buyer becoming aware of it⁹. Scheme-based cover uses the same thirty-day window³⁹.
2. Go through the installer or the maker's stated channel. Solplanet directs claimants to customer support or an online claim form³⁷; Enphase gives +44 (0)1908 828928⁵. Arranging an independent repair can void cover outright³³.
3. Gather evidence. Proof of purchase, serial numbers and the nature of the fault³².
4. Return within the RMA window. Enphase requires the allegedly defective covered product to be received within sixty days of it providing an RMA number, and may charge a restocking fee of the higher of 15 per cent of the original purchase price or the retail value of missing parts⁵.
5. Check the cover on the replacement. Under the Enphase terms the warranty continues on the repaired or replacement product for the remainder of the original period or ninety days from receipt, whichever is later⁵. A replacement does not restart the clock.

Recalls follow a different path from warranty claims and can be more generous. In the LG ESS home battery recall, LGESEG stated it would replace all affected batteries for free or provide a new module and remove the battery from the premises, with owners required to register the affected battery via the serial number checker page or by telephone or web⁴¹. Recall handling is covered under battery recalls and safety notices and the LG ESS recall.

Backup use, and what the warranty does not promise

Backup is where marketing and warranty text diverge most sharply. Not all batteries can deliver electricity during a power cut⁴², and network operator guidance is that in some cases storage devices can provide back-up supplies for use in a power cut, but this is not always possible and should be checked with the installer⁴³. Which? makes the same point: if the aim is protection against power cuts, not all systems are suitable, and the installer should be asked whether the battery will work in an outage and for how long⁴⁴. The hardware side is set out under battery backup in a power cut.

Even where backup works, the warranty may exclude critical use, as the Enphase life-support exclusion shows⁵. A warranty is a promise about defects and capacity, not about availability of supply on any given day.

Transfer on sale

Battery warranties generally follow the property when the equipment stays put, but the mechanism differs. The myenergi warranty is transferrable to a new owner of the property if the product is left behind, arranged through customer service³². The Rayleigh RI-ENERGYSET warranty is non-transferable except where the products are installed in a building, in which case it transfers to any subsequent purchaser of that building or of the products, so long as they remain installed²⁶. Enphase permits transfer but requires the applicable transfer fee set out in its change of ownership form to be paid within thirty days of the date of transfer⁵. Workmanship warranties pass automatically to the new owner for the remainder of the period¹³.

Because two of these require an active step within a short window, warranty transfer sits with the conveyancing paperwork rather than being assumed.

What a warranty means for household energy independence

A battery raises the share of electricity a home meets itself. MCS defines grid electricity independence as the percentage of electricity consumed in the property over a year met by behind-the-meter solar or electrical energy storage⁴⁵, and more homegrown energy is described as meaning greater energy independence⁴⁶. Batteries can also be charged from the grid at cheaper, lower-carbon times, the model behind the FlexBat concept of a mini home battery that stores grid energy when low-carbon power is abundant and takes over the load at carbon-intensive times⁴⁷.

The warranty is where the remaining dependencies become visible in writing. A fifteen-year Enphase term requires continuous internet connection and an activation record in the maker's portal⁵. A myenergi libbi loses its full term and falls to a 3MWh per kWh throughput cap if operated outside the maker's controller³². Powervault batteries are described as maintenance free, with proactive remote monitoring and remote fixes or site visits¹⁷: convenient, and another live link to a company. Every one of those clauses ties a self-generating household to a manufacturer's continued existence, its cloud service and its spare parts supply for a decade or more.

That is the honest position. Storage reduces dependence on a supplier's unit rate and on the timing of grid imports, and it does not remove dependence on the grid connection, the installer's continued trading, or the manufacturer's corporate survival. Independent advice on the trade-offs is available from the Energy Saving Trust, described as an independent organisation and trusted voice on energy efficiency solutions⁴⁸. Reading the warranty before purchase, specifically the start date, the usage limit, the connectivity clause and the reporting deadline, is the part of the buying process that determines whether a promise is worth anything ten years later. The broader picture is set out on the home battery storage guide and under home batteries and household energy independence.