Commercial solar warranties and guarantees explained
A modern commercial solar system is five stacked warranties from four different parties. Here's what each layer covers, where the gaps sit and how to make a claim that actually pays out.
The five layers of protection
Panel product warranty
Tier-1 manufacturers now offer 15–25 years product warranty on the panel itself against manufacturing defects. Longer isn't always better — check the transferability and the company's UK trading history.
Panel performance warranty
30-year linear performance guarantee, typically 87.4–92% of nameplate at year 30. This is what protects your revenue model against early degradation.
Inverter warranty
5–10 years standard, extendable to 20 (paid). Inverters are the most likely component to fail — always budget for at least one replacement over the array's life.
Workmanship / installer warranty
MCS installations require 2 years minimum; reputable commercial installers offer 5–10 years. Covers labour, mounting systems, cabling and workmanship — not the products themselves.
Insurance-backed guarantee (IBG)
Underwrites the installer's warranty if they cease trading. Essential for 10+ year contracts — insist on it, ask for the IBG certificate before paying deposits.
What to ask before you sign
- How many UK claims has this panel manufacturer paid in the last 3 years?
- Is the installer's workmanship warranty insurance-backed? Show the IBG certificate.
- Who handles the diagnostic — and does that cost fall on me?
- How is performance measured for a performance-ratio guarantee?
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FAQ
How long do commercial solar panel warranties last?
Modern tier-1 panels carry 25-year product and 30-year performance warranties. Inverters run 5–10 years standard (extendable). Workmanship is typically 5–10 years from a good commercial installer. Combined system cover is what matters — not any single number.
Are longer warranties always better?
No. A 30-year product warranty is only as good as the company backing it — check the manufacturer has been UK-active for 10+ years and has UK-based claims handling. Insurance-backed guarantees matter more than headline duration.
What is a solar performance guarantee vs a product warranty?
Product warranty covers panel defects (delamination, cell failure). Performance warranty guarantees output — e.g. "at least 87.4% of nameplate at year 30". You want both. Some installers add a third layer: a performance ratio guarantee for the system as a whole (>80% PR).
How do I claim on a solar warranty?
Keep the commissioning report, monitoring data and O&M logs. If output drops significantly (>3–5% below expectation), your O&M provider triggers a diagnostic. If a panel or inverter is at fault, they submit the claim to the manufacturer with test data and photos.
What is an insurance-backed guarantee (IBG)?
A separate insurance policy that pays out on the installer's workmanship warranty if the installer ceases trading. Underwritten by names like QANW, HomePro or IWA — costs £150–£600 for a 10-year policy. Insist on it: many installers active pre-2020 are no longer trading.
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