Solar Panel Degradation: What to Expect Over 25 Years
All solar panels lose efficiency gradually over time — this is called degradation. Quality panels from reputable brands degrade at 0.3–0.6%/year. After 25 years, a 0.55%/yr PERC panel retains 87% efficiency; a 0.45%/yr TOPCon retains 90.5%.
Degradation Rates by Panel Technology
| Technology | Degradation/yr | Year-25 Output | Best Brands |
|---|---|---|---|
| HJT (Heterojunction) | 0.25–0.30% | 93–94% | REC, Panasonic |
| TOPCon | 0.40–0.50% | 90–91% | Waaree, Vikram |
| Mono PERC | 0.50–0.60% | 87–88% | Adani, Tata |
| Polycrystalline | 0.60–0.80% | 83–85% | Older systems |
Quality panels carry a linear power output warranty — typically guaranteeing at least 80–82% output at year 25. Cheaper off-brand panels may degrade 2–3x faster and have no meaningful warranty backing.