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Solar Panel Degradation Calculator

See how LID and annual degradation reduce your system's output — and revenue — over 25 years.

Panel system
W
panels
%
%/yr
hrs/day
Technology & financials
$/kWh
%/yr
System size
8.0 kW
Year 1 annual output11,074 kWh
Output at year 107,494 W (10,586 kWh/yr)
Output at year 157,309 W
Output at year 256,951 W
Total lifetime kWh (25yr)260,867 kWh
Total kWh lost to degradation15,992 kWh
Revenue lost to degradation$3,933
80% warranty threshold> 25 years
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How to Use This Calculator

Enter your panel system details

Input your panel wattage (from the spec sheet), number of panels, and peak sun hours for your location (US average: 4–5 hrs/day). The calculator uses these to compute Year 1 production as your baseline.

Set the LID and degradation rate

Light-Induced Degradation (LID) is a one-time output loss in the first weeks of operation caused by boron-oxygen defects in standard silicon cells. It is separate from the ongoing annual degradation rate. Standard panels: 1–3% LID. Premium N-type/HJT panels: essentially 0%.

The panel technology dropdown auto-fills the manufacturer's rated annual degradation for that cell type, so you don't have to guess.

Read the year-by-year table

The expandable table shows output watts, annual kWh, cumulative kWh lost, and cumulative revenue lost for every year from 1–25. The summary shows the specific year when your panels cross the 80% output threshold — the standard warranty floor.

The Formula

System Watts Initial = Panel Wattage × Number of Panels Year 1 Output Watts = System Watts × (1 - LID%) Year N Output Watts = System Watts × (1 - LID%) × (1 - AnnualDeg%)^(N-1) Annual kWh (Year N) = Output kW × Peak Sun Hours × 365 × 0.86 Cumulative kWh Lost = ∑ (Year 1 kWh - Year N kWh), N=2..25 80% Warranty Year = First year where Output Watts < System Watts × 0.80

The 0.86 system efficiency factor accounts for inverter losses (~4%), wiring losses (~2%), temperature derating (~5%), and soiling (~3%). For a high-quality system in a cool climate, 0.88–0.90 is achievable. Hot climates (Arizona, Texas summer) may see 0.80–0.84.

Example

Standard 8 kW mono PERC system — 20 × 400 W panels

A homeowner in Phoenix installs 20 x 400W monocrystalline PERC panels. LID = 2%, annual degradation = 0.5%/yr, electricity rate $0.14/kWh, 6.0 peak sun hours.

Initial system8,000 W / 8.0 kW
Year 1 output7,840 W — 14,820 kWh
Year 10 output7,490 W — 14,165 kWh
Year 25 output7,000 W — 13,236 kWh
80% warranty thresholdYear > 25
Total 25-yr kWh lost~8,500 kWh
Revenue lost to degradation~$1,500

Mono PERC panels retain over 87% of initial output after 25 years. Compared to polycrystalline (0.6%/yr), the premium panel saves roughly 3,000 extra kWh and ~$500 over the system lifetime — a meaningful difference at scale.

FAQ

Solar panel degradation is the gradual reduction in a panel's electricity output over time. It is caused by UV exposure breaking down the ethylene-vinyl acetate (EVA) encapsulant, thermal cycling stressing cell connections, and moisture ingress over decades. A panel rated at 400 W in year 1 might produce only 350 W in year 25 at a 0.5%/yr rate. Degradation is inevitable but well-understood — it is why 25-year linear power warranties exist.
The industry benchmark is 0.5%/year for standard monocrystalline PERC panels. Premium technologies perform better: HJT panels (Panasonic, REC Alpha) degrade at 0.3%/yr; N-type TOPCon (Longi Hi-MO 6, Jinko Tiger Neo) at 0.35%/yr. Budget polycrystalline panels may degrade at 0.6–0.7%/yr. Thin-film (First Solar CdTe) averages 0.5–0.7%/yr but varies significantly by manufacturer. The NREL long-term study found a median degradation rate of 0.5%/yr across all technologies.
LID (Light-Induced Degradation) is a one-time, rapid output loss that occurs in the first hours to weeks of sunlight exposure. It is caused by boron-oxygen complexes forming in standard p-type silicon cells, reducing carrier lifetime. Typical LID: 1–3% for standard cells. It happens immediately after installation, then stabilizes. Long-term annual degradation is a separate, slower, continuing process. Premium N-type cells (HJT, TOPCon) do not use p-type silicon, so they have near-zero LID — one of their key advantages over PERC.
No — normal degradation is expected and accounted for in the warranty. A standard 25-year linear power warranty guarantees that output will not fall below 80% of nameplate power by year 25. If your panels degrade faster than that, the manufacturer owes you a replacement or credit. The warranty threshold is typically: 98% at end of year 1, then linear loss to 80% at year 25. Premium warranties (SunPower, REC, Panasonic) guarantee 92% at 25 years.
Choose panels with lower rated degradation (HJT or N-type TOPCon). Keep panels clean — soiling is not degradation but compounds effective output loss. Ensure adequate airflow under panels; heat accelerates degradation (roof-mount panels run hotter than ground-mount). Use quality mounting hardware to prevent micro-cracks from mechanical stress. Install in a location with low humidity if possible — moisture accelerates EVA delamination. Finally, choose a reputable installer who correctly torques racking to prevent panel flexing.

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