The short version
- There are four warranties, not one: panel product, panel performance, inverter, and installer workmanship.
- Panels rarely fail. Inverters and roof penetrations are where claims actually come from.
- A 25-year workmanship warranty is only worth as much as the company standing behind it.
- Ask who handles a claim — the installer, the manufacturer, or nobody in particular.
Four warranties, three companies
Nothing about a solar system is covered by a single document. A typical residential install carries four separate promises, and they are made by different parties with different incentives and different chances of still existing in fifteen years.
| Warranty | Who gives it | Typical term | What it covers |
|---|---|---|---|
| Panel product | Panel manufacturer | 12 – 25 yrs | Manufacturing defects in the panel itself |
| Panel performance | Panel manufacturer | 25 – 30 yrs | Output staying above a declining percentage |
| Inverter | Inverter manufacturer | 10 – 25 yrs | The box that converts DC to AC |
| Workmanship | Your installer | 1 – 25 yrs | The install: mounting, wiring, roof penetrations |
The spread on that last row is the important one. Workmanship warranties range from a legal minimum to a quarter of a century, and the difference is not cosmetic — it is the warranty most likely to be claimed against.
The performance warranty is the least useful number
Performance warranties are quoted as a guaranteed percentage of original output at a given year — typically around 85–92% at year 25, depending on the manufacturer and the panel line. Panels degrade slowly and predictably, roughly 0.4–0.6% a year for mainstream products.
This sounds like strong protection and rarely functions as any. To claim, you generally have to demonstrate that a specific panel is below the guaranteed curve, which means isolating it from the array and testing it under standard conditions. Very few homeowners ever do this. The remedy is usually a replacement panel, not a refund, and often excludes the labour to fit it.
Treat the performance warranty as evidence that the manufacturer is confident in its product — not as a benefit you are likely to use.
The inverter is what actually breaks
Panels have no moving parts and fail rarely. Inverters contain power electronics that run hot every day for decades, and they are the most common hardware failure in a residential system. Plan for the possibility of one replacement during the system's life.
- String inverters are usually warrantied 10–12 years, sometimes extendable to 20–25 for a fee. One unit serves the whole array, so a failure stops all production until it's replaced.
- Microinverters and DC optimisers are typically warrantied 25 years, matching the panels. One failing unit takes out one panel rather than the array — but there are as many of them as there are panels, all sitting on the roof.
Neither is universally better. What matters is whether the extended term is included or priced separately, and whether the labour to swap the unit is covered — a 25-year part warranty that leaves you paying for a roof visit and two hours of an electrician's time is a partial warranty.
Workmanship is the one to interrogate
Mounting, flashing, conduit runs and roof penetrations are the installer's work, and they are where real-world problems concentrate. A leak around a mount in year six is a workmanship issue, and the manufacturer warranties are irrelevant to it. See roof age and solar for why this overlaps with your roofing warranty too.
Three questions worth asking before you sign:
- How long is the workmanship warranty, in writing?Not "we stand behind our work" — a term, in the contract.
- Does it cover roof penetrations specifically?Some workmanship warranties carve out roof leaks, which is the main thing you wanted covered.
- Who services a claim if you are no longer trading?The honest answer is usually "the manufacturer for hardware, nobody for labour". Knowing that now is better than discovering it later.
A warranty is only as good as the company behind it
Residential solar has a high rate of company turnover. A 25-year workmanship warranty from a firm founded three years ago is a statement of intent, not a guarantee — and this is not a criticism of new companies so much as an observation about arithmetic.
Some manufacturers operate installer networks where another member takes over service if the original firm exits. Some financing arrangements bundle a monitoring and service agreement. Both are worth more than an extra five years on paper from a company that may not be there.