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.
<div class="tldr" style="border:1px solid #cbd5e1;background:#f8fafc;padding:16px 20px;border-radius:8px;margin:24px 0;"> <strong>Quick answer</strong> <ul> <li>Degradation is a gradual, predictable decline — not a fault or a failure point.</li> <li>Year one: ~1–2% loss (light-induced degradation). After that: ~0.3–0.55%/year on quality panels.</li> <li>A "25-year performance warranty" guarantees a minimum output percentage, not that the panel keeps physically working.</li> <li>Dirt, shading and connector/inverter faults usually cost more real output than cell degradation.</li> </ul> </div>
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:
<div style="overflow-x:auto;"> <table style="border-collapse:collapse;width:100%;min-width:480px;"> <thead><tr style="background:#eef2f7;"> <th style="border:1px solid #cbd5e1;padding:8px;text-align:left;">Milestone</th> <th style="border:1px solid #cbd5e1;padding:8px;text-align:left;">Guaranteed minimum output</th> </tr></thead> <tbody> <tr><td style="border:1px solid #cbd5e1;padding:8px;">End of Year 1</td><td style="border:1px solid #cbd5e1;padding:8px;">No less than ~98% of rated capacity</td></tr> <tr><td style="border:1px solid #cbd5e1;padding:8px;">Years 2–25 (per year)</td><td style="border:1px solid #cbd5e1;padding:8px;">Decline of no more than ~0.4–0.5%</td></tr> <tr><td style="border:1px solid #cbd5e1;padding:8px;">Year 25</td><td style="border:1px solid #cbd5e1;padding:8px;">No less than ~87–90.5% of rated capacity</td></tr> </tbody> </table> </div>
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.
