Panel Degradation Calculator
See how your panel output changes over 50 years
Panel degradation over time
Solar panels lose output gradually each year. The shaded band shows the typical range for your panel type. Drag the slider to explore best and worst cases.
10 panels
4.5 kW system
2% first-year loss
After year 1
3,969
98% (2% LID loss)
Year 25
3,519
87% of original
Year 50
3,105
77% of original
50yr total
180k
kWh generated
Mono-PERC panels lose ~2% in year one from Light-Induced Degradation (LID), then degrade linearly. The 25-year warranty guarantees at least 80% output. Field data beyond 30 years is limited — projections past that point are modelled, not measured.
How this works
Solar panels lose output over time through two mechanisms: first-year Light-Induced Degradation (LID), which drops output by 1-2% in the first weeks, then linear annual degradation of 0.3-0.7% thereafter.
Mono-PERC panels (the most common) lose about 2% in year one plus 0.5%/year ongoing. N-type TOPCon and HJT panels are immune to boron-oxygen LID, losing only 1% in year one and degrading more slowly at 0.25-0.4%/year.
The typical 25-year warranty guarantees at least 80% of original output (84-87% for N-type). Real-world data from panels installed in the 1980s shows many still producing at 80-90% after 30-40 years.
Things to consider
- •Sustained degradation above 1.5%/year indicates a fault, not normal ageing — investigate immediately.
- •Hot climates accelerate degradation. UK panels typically outperform the manufacturer warranty by a comfortable margin.
- •Glass-glass modules with polyolefin encapsulants are the most durable — worth paying a premium for if you plan to stay in your home long-term.
- •Degradation is gradual and predictable. Sudden output drops point to specific failures (cracked cells, bypass diode, connector corrosion).
Dig deeper
Solar Panel Degradation: How Much Output Do You Lose?
Solar panels lose output over time through degradation. How much, how fast, and what it means for your long-term returns from solar in the UK.
How Long Do Solar Panels Last? The Honest Answer
Solar panels are rated for 25–30 years, but what does that actually mean? Degradation rates, warranty types, what happens after 25 years, and why inverters are the weak link.
PERC vs N-type TOPCon vs HJT: Solar Panel Technology Compared for 2026
The three solar cell technologies available in the UK right now. How they differ in efficiency, degradation, temperature performance, and value — with real prices.
Solar Panel Efficiency: What It Means and Why It's Not Everything
Panel efficiency explained plainly — what the percentage actually means, why the gap between 20% and 22% barely matters for most UK homes, and what you should actually be comparing.
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