The standard pitch is "25-year performance warranty." People often interpret this as "they last 25 years and then stop working." Neither part of that is quite right.
What Actually Happens Over Time
Solar panels degrade gradually — they don't suddenly stop working at year 25. The degradation process is slow and predictable:
- Year 1: Panels undergo their biggest single-year drop, typically around 0.5–1%, as the manufacturing residue bakes off under UV exposure. This is normal and expected.
- Years 2–25: Annual degradation of roughly 0.3–0.5% per year for quality panels. At 0.4%/year, a panel rated 400W today will produce about 360W at year 25 — still 90% of original output.
- After year 25: Many panels keep going. There are working Australian systems from the 1990s still on roofs, generating electricity. They're less efficient than modern panels, but they work.
What the Performance Warranty Actually Guarantees
Australian law requires all solar panels sold here to come with a minimum 25-year performance warranty guaranteeing at least 80% of original output at year 25. Premium brands (REC, SunPower Maxeon, Aiko) warrant 87–92% at year 25, with degradation rates as low as 0.25%/year.
The 80% floor means: at worst, a 400W panel should still produce 320W after 25 years. In practice, quality panels significantly outperform this floor.
What Cuts Lifespan Short
Most early panel failures come from factors other than natural degradation:
- Poor installation: Incorrect mounting, inadequate sealing, or improper wiring can cause premature failure. This is a workmanship issue, covered by the installer's warranty — another reason the workmanship warranty matters.
- Hail and physical damage: Australian standard panels (IEC 61215 certified) must survive 25mm hailstones at 23m/s. Large hail events can cause damage; check your home and contents insurance covers this.
- Delamination: Where the protective layers separate, allowing moisture to enter and cause cell corrosion. Usually a manufacturing defect — covered by product warranty.
- Low-quality panels: Budget panels from unknown manufacturers degrade faster and fail earlier. One study found roughly 20% of panels examined failed much faster than expected — almost always cheaper or counterfeit products.
The Inverter Is the Weak Link, Not the Panels
If your panels last 25+ years, your inverter almost certainly won't. Standard string inverters typically last 10–15 years. You should budget for one inverter replacement over the life of your system — typically $1,500–$2,500 installed. This is a known cost, not a surprise, and it doesn't undermine the economics.
Microinverters (which have one small inverter per panel) typically carry 25-year warranties to match the panels, eliminating the mid-life replacement issue — at higher upfront cost.
What This Means for Your Payback Calculation
A well-installed system from a quality manufacturer, maintained normally, should produce meaningful electricity for 30+ years. The 25-year payback models used by most installers are conservative — the economic life of the system is likely longer than the model assumes.
The key is starting with good gear and a good installer. Once it's on your roof and working, the math takes care of itself.
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