Solar panel warranties explained

A solar installation carries at least four separate warranties, and they cover different things from different parties. The panel product warranty covers manufacturing defects. The panel performance warranty covers output falling below a stated level. The inverter, battery and other components each carry their own manufacturer cover. And the installer provides workmanship cover for the installation itself — the fixings, the weathering and the electrical work. Reading a quotation properly means seeing all four, not the single headline figure that gets advertised.

Product warranty

This covers defects in materials and manufacture: delamination, frame failure, junction box faults, moisture ingress, cell defects.

Two questions matter more than the headline period. First, what does it actually deliver — a replacement panel only, or replacement plus labour and access? Many cover the component alone, which on a roof-mounted array leaves the expensive part with you.

Second, who honours it? A manufacturer warranty is only as good as the manufacturer’s continued existence and its UK support arrangements. A long period from a company with no European presence is worth less than a shorter one from a manufacturer with an established support operation.

Performance warranty

Separate from the product warranty, and separate in what it promises. It states that output will not fall below a defined percentage of the original rating over a defined period, usually with a higher figure at year one and a declining schedule thereafter.

Claiming under it is harder than claiming for a broken panel. You have to demonstrate that a specific module is producing below the warranted level under standard conditions, which usually means testing rather than pointing at a monitoring app. Systems with module-level monitoring make that argument far easier to build.

Inverter and battery warranties

Inverters have a shorter service life than panels and are the component most likely to need attention during a system’s life. Their warranty periods are usually shorter to match.

Check whether the cover is on-site or return-to-base. Return-to-base means removing the unit and shipping it, with the system down while that happens. Check whether extensions can be purchased and whether that has to be done at installation or can be done later.

Battery warranties typically combine a period with a throughput or cycle limit, plus a retained capacity figure — whichever comes first. The capacity figure is the useful one: it tells you what the manufacturer expects the battery to hold after the stated period of use.

Workmanship warranty

This is the installer’s own cover for their work: roof fixings, weathering, cabling, electrical work and commissioning. It is the one that matters when water appears in a bedroom, and it is the one most likely to be tested in the first few years.

Ask three things. What does it cover — roof penetrations and weathering as well as electrics? How long does it run? And what happens if the installer ceases trading? Insurance-backed guarantees exist for exactly that scenario and are worth understanding rather than assuming.

MCS certification is relevant here too. It is the standards scheme covering both products and installers for small-scale renewables, and certified installers are audited against installation standards. It is not a warranty, but it is evidence that the work was carried out within a certified framework.

Common exclusions

Read these before you need them.

• Damage from extreme weather, which is generally an insurance matter rather than a warranty one
• Damage caused by cleaning, particularly pressure washing
• Damage from birds, rodents and nesting activity
• Installation outside the manufacturer’s instructions, including clamping outside permitted zones
• Mismatched DC connectors from different manufacturers — a real and frequently-encountered exclusion
• Modification or repair by anyone other than an approved contractor
• Consequential loss, including lost generation and lost export income

Making a claim work

Keep the paperwork from day one: MCS certificate, Electrical Installation Certificate, DNO documentation, warranty registrations in your name, panel and inverter serial numbers, commissioning records and the system design. Store it digitally as well as on paper.

Then keep evidence of performance. Monitoring history is what turns “it seems low” into a documented decline with a date attached. Where a fault is intermittent, records over time are the difference between a claim and an argument.

When something goes wrong, contact your installer first. Describe what changed and when, and send monitoring data with it.

What to ask before you sign

Ask for the warranty documents themselves, not a summary in a brochure. Ask specifically whether labour and access are included on each. Ask who registers the warranties and in whose name. Ask what workmanship cover the installer provides and whether it is insurance-backed.

A quotation that answers all of that is one you can compare properly. One that gives four numbers and no documents is not.