“25-year warranty” is one of the most-used phrases in solar marketing — and one of the most misunderstood. The trap is assuming it’s a single, simple promise. It isn’t. A solar system actually comes with three different warranties, each covering something different, and a headline “25-year warranty” might refer to only one of them while the others are far shorter. Knowing the difference is how you avoid a nasty surprise years down the track. Here are the three that matter.
1. The product (manufacturer’s) warranty
This covers manufacturing defects — the panel itself failing or being faulty because of how it was made. If a panel delaminates, cracks without external cause, or simply stops working because of a defect, the product warranty is what covers a replacement.
- What to look for: product warranties on panels typically run 12 to 25 years. Longer is better, and a longer product warranty often signals a manufacturer confident in their build quality.
- The catch: a “25-year warranty” advertised on a panel is sometimes the performance warranty (below), with a shorter product warranty underneath. Always check the product warranty term specifically.
2. The performance warranty
This is a different promise: it guarantees the panel will still produce a minimum amount of power over time, accounting for the slow degradation all panels experience. It’s usually the one that’s “25 years”.
- What it guarantees: typically that the panel will still output at least 80–92% of its rated power at year 25. So it protects you against a panel fading faster than it should.
- What it doesn’t do: it’s about output over time, not defects. A panel can be within its performance warranty and simply be old — this warranty won’t replace it for ageing normally.
3. The workmanship (installer’s) warranty
This is the one people forget, and it’s arguably the most practically important. It covers the installer’s own work — the mounting, the wiring, the labour. If a panel comes loose, a roof penetration leaks, or there’s a wiring fault that’s down to how it was installed rather than a faulty product, the workmanship warranty is what covers it.
- What to look for: a clear workmanship warranty from the installer, ideally several years or more.
- Why it matters: the manufacturer’s warranties cover the products; only the workmanship warranty covers the installation. Since poor installation is a leading cause of real-world problems, this is the warranty that protects you against the most likely issues — and it’s only as good as the installer still being in business to honour it.
The trap to avoid
The headline-warranty trap works like this: an installer advertises “25-year warranty”, you assume everything’s covered for 25 years, and only later discover the product warranty was 10 years, or the workmanship warranty was barely there. The fix is simple — ask for all the warranty terms in writing, separately:
- Panel product warranty (years)
- Panel performance warranty (years and % output)
- Inverter warranty (often 5–10 years, sometimes extendable)
- Workmanship warranty (years)
And remember: every warranty depends on the company behind it still existing. A warranty from a reputable, locally-supported brand and a well-established installer is worth far more than a longer number from an outfit that may vanish.
The verdict
A solar “warranty” is really three: the product warranty (defects, 12–25 years), the performance warranty (output over time, typically 80–92% at 25 years), and the workmanship warranty (the installer’s own work). A headline “25-year warranty” usually means just one of them, so the smart move is to get all the terms in writing — including the inverter’s — and to weigh them by whether the brand and installer will actually be around to honour them. That’s how you avoid a warranty that doesn’t cover what you assumed.
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Sources: Product, performance, and workmanship warranty norms per manufacturer and NZ industry references (2026). Terms vary by brand and installer; confirm in writing.