Degradation is real and measurable. We walk through the numbers, explain the year-1 LID dip, compare manufacturer warranties, and show how much it changes the long-run savings estimate.
Direct answer
Modern monocrystalline solar panels degrade at roughly 0.4??.7% per year after an initial year-1 LID (light-induced degradation) drop of 1??%.
After 25 years, a panel rated at 400W typically outputs around 340??60W ??about 85??0% of original nameplate capacity.
Most leading manufacturers warrant 80??7% output at year 25. Solar Payback Map models degradation at 0.5%/yr, consistent with NREL median research.
Key takeaways
- Modern monocrystalline solar panels degrade at roughly 0.4??.7% per year after an initial year-1 LID (light-induced degradation) drop of 1??%.
- After 25 years, a panel rated at 400W typically outputs around 340??60W ??about 85??0% of original nameplate capacity.
- Most leading manufacturers warrant 80??7% output at year 25. Solar Payback Map models degradation at 0.5%/yr, consistent with NREL median research.
Evidence snapshot
This article was reviewed by Solar Payback Map Editorial against public solar payback sources and the Solar Payback Map editorial policy.
Panels get slightly less productive every year
Solar panel degradation is the gradual reduction in output caused by UV exposure, thermal cycling, humidity ingress, and chemical changes in the silicon. It is measurable, predictable, and already factored into manufacturer warranties.
The industry median is approximately 0.5% efficiency loss per year. That means a panel producing 1,000 kWh in year one produces about 995 kWh in year two, 990 kWh in year three, and about 880 kWh in year 25. It is not dramatic ??but it is real, and it belongs in any honest 25-year savings estimate.
Year-one LID: the first-year performance dip
Light-induced degradation (LID) is a different phenomenon from long-term wear. It happens in the first several hours to days of sun exposure as boron-oxygen defects form in crystalline silicon cells.
LID typically causes a 1??% output reduction in year one alone. High-quality panels are pre-tested or use LID-resistant cell technology (n-type TOPCon, HJT). Budget monocrystalline panels may experience higher LID. After the initial LID, the degradation rate stabilizes to the long-term 0.4??.7%/yr trajectory.
Power warranty vs product warranty: two different guarantees
Panels come with two warranties. The product warranty (10??5 years, sometimes 25 years) covers manufacturing defects and physical failure. The power warranty guarantees minimum output at specific time points.
| Manufacturer tier | Year-1 minimum |
|---|---|
| Budget (polycrystalline) | 97.5% |
| Mid-range mono | 98.0% |
| Premium (mono/TOPCon) | 98.0% |
| Solar Payback Map model assumption | - |
How much degradation changes the 25-year savings estimate
At 0.5%/yr, a 10 kW system producing 10,000 kWh/year initially produces about 231,000 kWh over 25 years ??versus 250,000 kWh at no degradation. That 7.6% production reduction translates directly to 7.6% lower 25-year savings.
On a $21,000 net cost system saving $2,500/year in year one, the undegraded 25-year estimate is about $41,500 net. With realistic 0.5% degradation modeled, it comes to about $38,000 net ??a $3,500 difference that optimistic installers often omit.
Degradation is not failure
A panel degrading at 0.5%/yr is working correctly. It is not failing. Actual failure ??cracking, delamination, junction box issues ??is what the product warranty covers and is less predictable.
Degradation projections assume a working panel. A panel that fails outright before year 25 is a warranty claim, not a degradation event. Installers with strong product warranties and responsive service teams matter more for this risk than the panel brand alone.
FAQ
- Do all solar panels degrade at the same rate?
- No. Panel technology and quality affect degradation rate. N-type cells (TOPCon, HJT, IBC) generally degrade slower (0.3??.45%/yr) than standard p-type mono panels (0.5??.7%/yr). Polycrystalline panels are generally on the higher end. Premium manufacturers publish independent third-party degradation test data ??ask for it if it matters to your decision.
- Should I oversizing my system to account for degradation?
- Sometimes. If your utility allows a net metering credit for excess production, oversizing slightly (10??5%) can offset year-25 output reduction. However, oversizing increases upfront cost and may exceed interconnection limits in some utility territories. Run the numbers in the calculator before assuming oversizing is worth it.
Next step
Sources and further reading
Editorial review
- Reviewed against public sources listed above, not installer lead-generation data.
- Written for homeowner decision quality, with conservative assumptions favored over sales optimism.
- Updated and checked for policy, rate, source, and quote-risk context.
Read the Solar Payback Map editorial policy and Solar Payback Map Editorial profile for source, correction, advertising, authorship, and review standards.
This article is general information, not financial, tax, legal, or engineering advice. Verify current incentives, utility tariffs, and quote-specific assumptions before relying on any estimate.