Solar Panel Degradation Calculator
Project solar panel output over its lifetime using first-year and annual degradation rates, and see the year-25 figure.
Results
The first year is different
Panels lose more in their first year than in any year that follows — typically 1 to 3 % from light-induced degradation, after which the curve flattens to roughly half a per cent a year. Warranties are written around exactly this shape.
What the warranty actually promises
A typical performance warranty guarantees around 80 to 85 % of rated output at year 25. That is a floor, not a forecast: panels installed in the 1990s are still running well above their guaranteed figures. Degradation is real, but it is slow and predictable, and it is not the reason most systems underperform.
Common mistakes
Blaming degradation for a sudden drop in output. Degradation is gradual and measured in fractions of a per cent a year. A step change points at soiling, shading, a failed optimiser or a string that has gone open circuit.
Questions people ask
Do panels stop working after 25 years? No. Twenty-five years is the warranty horizon, not a lifespan. Well-installed arrays commonly run beyond thirty at reduced output.
Which degrades fastest? Thin-film generally more than crystalline silicon, and any panel with a compromised seal far faster than the datasheet suggests.