Panel degradation
The gradual yearly loss of a solar panel's output — typically about 0.4–0.5% per year, so panels still make ~85–90% of original power at 25 years.
All solar panels lose a little output each year as the cells age. Modern monocrystalline modules degrade around 0.4–0.5% annually, and manufacturers warranty performance at roughly 85–90% of nameplate after 25 years.
Degradation matters for payback math: each year your array produces slightly fewer kilowatt-hours, which is why long-term savings estimates apply a small annual production haircut alongside rising utility rates.
Put it to work
See also