About the Degradation & Aging
Solar module degradation is the gradual loss of output as panels age. It determines how much energy — and savings — a system delivers in later years, and underpins the manufacturer's performance warranty.
Formula
Output(year n) = Rated × (1 − d₁) × (1 − d)ⁿ⁻¹
- d₁
- First-year degradation (typically ~2%)
- d
- Annual degradation thereafter (~0.5–0.7%)
- n
- Year number
How to calculate it
- 1Apply a higher first-year 'light-induced degradation' step (around 2% for crystalline silicon).
- 2Apply a steady annual degradation of roughly 0.5–0.7% per year thereafter.
- 3Project output year by year to estimate lifetime energy and check it against the warranty curve.
Worked example
A panel with 2% first-year and 0.6%/year degradation retains about 100 × (1−0.02) × (1−0.006)²⁴ ≈ 85% of its rated output at year 25 — consistent with typical 25-year 80–87% performance warranties.
What you can calculate
- 25-yr model
- Yr 10/25 warranty
- Revenue lost
- Year-by-year table
Standards & references
Frequently asked questions
How long do solar panels last?
Quality crystalline-silicon panels are warranted for 25 years and commonly keep producing beyond that. Most carry a performance warranty guaranteeing roughly 80–87% of rated output at year 25, reflecting typical degradation of about 0.5–0.7% per year after the first year.
You might also need
Energy Generation
Calculate daily, monthly, and annual generation from kWp, PSH, and PR with revenue projection
OpenPerformance Ratio (PR)
Calculate IEC 61724 performance ratio from actual vs theoretical generation and grade the result
OpenCUF / PLF Calculator
Calculate Capacity Utilisation Factor and Plant Load Factor with India state-wise benchmarking
OpenPlant Loss Breakdown
9-step loss waterfall from irradiation to net energy — quantify every loss category
OpenTemperature Loss
Quantify power derating from cell temperature using NOCT model per IEC 61215
OpenShading Loss
Estimate annual energy and revenue lost due to near and far shading obstructions
Open