All solar panels lose a small amount of output every year. Most modern panels are warrantied to still produce 85–92% of their original output after 25 years.
Typical degradation rates
- First-year drop: around 1–2% (light-induced degradation).
- Every year after: 0.3%–0.8% depending on the panel.
- Premium tier-1 panels sit at the low end of that range.
What that looks like in practice
A 4kWp system that produces 3,500 kWh in year one will typically still produce around 3,000–3,150 kWh in year 25 — a small change relative to the savings you'll have banked by then.
What accelerates degradation
Poor mounting, water ingress at connectors, and physical damage. All avoidable with a good install and occasional inspection.