There is no such thing as “the warranty” on a solar system. There are four, and they cover different things, come from different parties and last different lengths of time.
The four
1. Panel product warranty Covers the panel physically failing. From the manufacturer. Commonly 12 to 25 years depending on the maker.
2. Panel performance warranty Guarantees a minimum output after a given number of years, for example a stated percentage of original output at year 25. Also from the manufacturer, and separate from the product warranty. A panel can be underperforming without having failed.
3. Inverter warranty From the inverter manufacturer. Typically shorter than the panel warranty, which tells you something about expected life. Often extendable at additional cost.
4. Workmanship warranty From the installer. Covers the installation itself: the mounting, the roof penetrations, the cabling, whether it leaks. Length varies a great deal.
A battery has its own warranty too, making five if you have one.
The question that catches people out
Does the warranty cover the labour of replacing the part, or only the part?
Most manufacturer warranties cover the component. They do not cover getting on your roof to fit it. A free replacement panel in year fourteen still needs scaffolding and a day’s labour, which can cost more than the panel.
Ask each installer:
- Does your workmanship warranty cover labour for a warranty replacement?
- For how long?
- Who pays for scaffolding and access?
The answer varies enormously between installers and it is one of the more meaningful differences between two otherwise similar quotes.
The other question: will they still be there?
A 25-year warranty is a promise from a company that has to exist in 25 years to honour it.
This is not theoretical in solar. Several manufacturers prominent enough to warrant their own review pages a decade ago have since collapsed, been delisted or left the industry. Installation companies fail too.
So ask:
- Does the panel manufacturer have a UK office or UK distributor?
- How would I actually make a claim in year twelve?
- Is there an insurance-backed guarantee behind the workmanship warranty?
That last one matters most An insurance-backed guarantee means the workmanship warranty is underwritten by an insurer rather than resting on the installer still trading. Installers belonging to a consumer code often offer one. It is worth asking about specifically.
Battery warranties
Battery warranties are often stated differently from the others, in one of three ways:
- Years, straightforwardly
- Cycles, a number of charge and discharge cycles
- Throughput, a total amount of energy passed through the battery
Whichever comes first usually applies. A warranty may also guarantee a minimum remaining capacity at the end of the term, for example a stated percentage of original capacity.
Work out which limit you would realistically hit first. If you plan to charge overnight from a time-of-use tariff every night, you will cycle the battery much harder than someone using it only for solar surplus, and a cycle-limited warranty may expire well before its stated years.
What to check in a quote
- All four warranties, in writing, with lengths stated separately
- Whether labour and access are covered, and for how long
- Whether there is an insurance-backed guarantee, and who underwrites it
- The battery warranty basis: years, cycles or throughput
- What happens if the installer ceases trading
- What voids the warranty. Cleaning by the wrong method, for example, or work by another contractor
Keep the paperwork
Keep the Microgeneration Certification Scheme (MCS) certificate, the electrical certificate, the warranty documents and the handover pack together somewhere you will find them. You need the MCS certificate to claim the Smart Export Guarantee, and you need the rest if you ever claim or sell the house.