25-Year Degradation Model
Professional export income forecast with panel degradation
Industry-First Analysis
No UK solar site has published a degradation-adjusted 25-year export forecast. This model uses industry-standard degradation rates:
- •Year 1: -2.0% (Light-Induced Degradation — LID)
- •Years 2-25: Standard panels -0.5%/year, Premium -0.3%/year, Budget -0.8%/year
- •Three scenarios: Optimistic (SEG rate +2%/yr), Typical (flat), Pessimistic (SEG rate -1%/yr)
System Configuration
PVGIS: 870 kWh/kWp/year
25-Year Forecast
| Year | Cal Year | Degrad% | Gen kWh | Export kWh | SEG £ | Total £ | Cumulative £ |
|---|---|---|---|---|---|---|---|
| 1 | 2027 | 98% | 3,410 | 1,194 | £286 | £907 | £907 |
| 2 | 2028 | 97.5% | 3,393 | 1,188 | £285 | £903 | £1,810 |
| 3 | 2029 | 97% | 3,376 | 1,182 | £284 | £898 | £2,708 |
| 4 | 2030 | 96.5% | 3,359 | 1,176 | £282 | £894 | £3,602 |
| 5 | 2031 | 96.1% | 3,343 | 1,170 | £281 | £889 | £4,491 |
| 6 | 2032 | 95.6% | 3,326 | 1,164 | £279 | £885 | £5,375 |
| 7 | 2033 | 95.1% | 3,309 | 1,158 | £278 | £880 | £6,256 |
| 8 | 2034 | 94.6% | 3,293 | 1,152 | £277 | £876 | £7,132 |
| 9 | 2035 | 94.1% | 3,276 | 1,147 | £275 | £872 | £8,003 |
| 10 | 2036 | 93.7% | 3,260 | 1,141 | £274 | £867 | £8,870 |
| 11 | 2037 | 93.2% | 3,244 | 1,135 | £272 | £863 | £9,733 |
| 12 | 2038 | 92.7% | 3,227 | 1,130 | £271 | £859 | £10,592 |
| 13 | 2039 | 92.3% | 3,211 | 1,124 | £270 | £854 | £11,446 |
| 14 | 2040 | 91.8% | 3,195 | 1,118 | £268 | £850 | £12,296 |
| 15 | 2041 | 91.4% | 3,179 | 1,113 | £267 | £846 | £13,141 |
| 16 | 2042 | 90.9% | 3,163 | 1,107 | £266 | £841 | £13,983 |
| 17 | 2043 | 90.4% | 3,148 | 1,102 | £264 | £837 | £14,820 |
| 18 | 2044 | 90% | 3,132 | 1,096 | £263 | £833 | £15,653 |
| 19 | 2045 | 89.5% | 3,116 | 1,091 | £262 | £829 | £16,482 |
| 20 | 2046 | 89.1% | 3,101 | 1,085 | £260 | £825 | £17,307 |
| 21 | 2047 | 88.7% | 3,085 | 1,080 | £259 | £821 | £18,127 |
| 22 | 2048 | 88.2% | 3,070 | 1,074 | £258 | £817 | £18,944 |
| 23 | 2049 | 87.8% | 3,054 | 1,069 | £257 | £812 | £19,756 |
| 24 | 2050 | 87.3% | 3,039 | 1,064 | £255 | £808 | £20,565 |
| 25 | 2051 | 86.9% | 3,024 | 1,058 | £254 | £804 | £21,369 |
Understanding the Model
What is LID?
Light-Induced Degradation (LID) is a well-documented phenomenon where crystalline silicon solar panels experience accelerated degradation in the first few weeks of operation. Modern panels typically see 2% degradation in year 1, then stabilize to 0.5%/year for standard panels.
How Accurate Is This?
These degradation rates are based on NREL (National Renewable Energy Laboratory) studies of real-world panel performance across thousands of installations. Premium panels from manufacturers like Panasonic and SunPower offer warranties guaranteeing <0.3%/year degradation.
Why Three Scenarios?
SEG (Smart Export Guarantee) rates are not guaranteed to remain constant. The Optimistic scenario (+2%/yr) models rates increasing with retail electricity prices. The Pessimistic scenario (-1%/yr) models rates declining as solar becomes more common. The Typical scenario assumes flat rates.
For Installers & Consultants
This model is designed for professional use. When quoting long-term export income to clients, showing degradation-adjusted figures demonstrates technical competence and manages expectations. Export this data to PDF using our report generator.
Need Help With This Data?
Scottish Energy Efficiency provides professional solar export analysis for commercial properties, installer quotes, and surveyor reports.