The degradation rate is the gradual yearly decline in a solar panel's output as its materials age. Panel warranties guarantee a minimum output after a set number of years, which implies a maximum yearly decline; actual degradation depends on the panel technology, climate and installation quality. A slower rate means more energy over the life of the system and slightly better long-term savings. Our calculator applies a constant yearly degradation to production, and you can change it in the advanced assumptions to match the warranty on your quote. When comparing panels, look at the product warranty and the power warranty separately; they often run for different periods.
Related terms and pages
- PVWatts: A free model from the national laboratory formerly called NREL that estimates solar output for any location.
- Payback period: The number of years until a solar system's savings equal what you paid for it.
- Calculator methodology