Every solar panel produces slightly less electricity each year — that's normal, expected, and accounted for in every reputable warranty. Quality monocrystalline panels typically lose around 1–2% in the first year as they stabilise, then just 0.3–0.55% per year after that, leaving roughly 87–90% of original output at year 25. Understanding degradation properly helps you read a spec sheet correctly, compare brands honestly, and know what "25-year warranty" actually promises versus what it doesn't.
Degradation is the gradual decline in a panel's power output over time, measured as a percentage of original rated capacity. A panel rated at 440W on day one won't produce exactly 440W under identical test conditions ten years later — it will produce a little less, because the physical and chemical processes inside the cell slowly wear. This isn't a fault or a defect; it's a predictable material characteristic, which is why manufacturers publish degradation curves.
Several physical mechanisms act together:
This is where most homeowners misread the fine print. A performance warranty doesn't promise the panel will last 25 years in the sense of "still working." It guarantees a minimum output percentage relative to original rated capacity, at specific milestones. A typical premium panel's performance warranty:
| Milestone | Guaranteed minimum output |
|---|---|
| End of Year 1 | No less than ~98% of rated capacity |
| Years 2–25 (per year) | Decline of no more than ~0.4–0.5% |
| Year 25 | No less than ~87–90.5% of rated capacity |
If your panel underperforms this curve — verified through testing — the manufacturer is obligated to repair, replace or compensate. It says nothing about the panel continuing to physically survive; that's covered by a separate, shorter warranty.
These three get conflated constantly but cover completely different things (full detail in Solar Panel Warranty Types Explained):
Always check both performance and product warranty, and confirm who is standing behind each — an offshore manufacturer with no Australian presence is a very different proposition to one with a local support office.
For a typical 6.6kW residential system in the Sydney basin, a realistic degradation profile means your system might produce close to its rated output in year one, and still be producing around 88–92% of that original output after 25 years, assuming quality panels and no physical damage. That's a very small annual loss — often barely noticeable against the bigger year-to-year swings from weather and seasonal daylight.
The bigger real-world risk to output usually isn't cell degradation at all — it's dirt and dust build-up, shading from growing trees, or a connector/inverter fault, all avoidable with basic maintenance and monitoring.
Most modern hybrid and string inverters offer app-based monitoring showing daily, monthly and yearly production. Comparing like-for-like months year-on-year (accounting for weather) is the simplest way to spot whether your system is degrading faster than expected, or whether something else — a faulty string, shading, a dirty panel — is the real cause.
Quality monocrystalline panels typically degrade about 0.3–0.55% per year after an initial ~1–2% first-year settling; lower-tier panels can be 0.7–0.8% or more.
Almost certainly yes — they'll produce roughly 87–90% of their original output, not zero. Performance declines gradually rather than stopping abruptly.
Not sure whether your system's output is tracking normally, or want a like-for-like comparison of panel brands and their real-world warranty terms? Get a tailored assessment from Blue Energy Solar, or call 0421 458 217.
