Help CenterPerformance & Lifetime
Solar panel degradation over time
Performance4 min readUpdated: 2026-08
A solar panel's power output decreases every year, even without any defect. This degradation combines a fast initial loss followed by a slow linear decline over the product's lifetime.
| Phase | Typical loss | Cause |
|---|---|---|
| LID — first exposure | 1–3% (one-time) | Light-Induced Degradation: silicon stabilization in the first hours of exposure |
| LeTID (some PERC panels) | 0–2% (one-time, over ~1 year) | Light and Elevated Temperature Induced Degradation, mostly hot climates |
| Annual linear degradation | 0.4–0.6%/year (mono) | Normal aging of cells and encapsulant |
P(n) = P0 × (1 − LID) × (1 − r)^nP0 = rated power · LID = initial loss (≈0.02) · r = annual rate (≈0.005) · n = years
400 W
New panel
392 W
After 1 year (LID)
−2%
374 W
After 10 years
≈ −6.5% cumulative
340 W
After 25 years
manufacturer warranty ≥ 80–84.8%
Most manufacturers guarantee ≥ 80% power after 25 years (linear performance warranty), distinct from the product warranty (manufacturing defects, often 10–15 years). Check both separately.
Common mistakes
- Sizing the system on rated power with no margin for the next 20–25 years
- Confusing product warranty (defects) with performance warranty (power over time)
- Ignoring LeTID for PERC panels installed in a hot climate