Every solar panel loses a small amount of output every year — this is normal and priced into every proposal.
What the curve looks like
- A small first-year dip (~2%), then a steady ~0.5% per year after.
- Tier-1 panels degrade more slowly than budget alternatives.
- Heat, humidity and poor installation quality can accelerate it.
"A panel at year 20 still produces roughly 90% of its day-one output — degradation isn't decay, it's a slow taper."
| Year | Output |
|---|---|
| 1 | 98% |
| 10 | ~94% |
| 25 | ~83% |
This curve is exactly why ROI calculations assume 25, not 30, years of full credit.