Solar Panel Degradation Calculator
Project solar panel output over 25 or 30 years from first-year loss and annual degradation, with lifetime energy.
Quick answer
Solar panel output after n years is P(n) = 1 − LID − d × (n − 1), where LID is the first-year loss and d the yearly rate. An n-type TOPCon panel warranted at 1% in year 1 and 0.40% a year keeps 87.4% of its rating after 30 years. An 8 kW system making 11,000 kWh when new then produces about 307,560 kWh over 30 years.
How to use the solar panel degradation calculator
- Pick a warranty profile. Choose the line that matches your panel’s linear power warranty, or Custom to type the first-year loss and yearly rate from your datasheet.
- Choose 25 or 30 years. Most PERC warranties run 25 years and most n-type warranties 30.
- Enter the system size and first-year output. Type the kW and the kWh a year the system makes when new. The solar panel output calculator gives that figure for your location. Enter 0 kWh to skip the energy cards.
- Read the output after 25 or 30 years. The big number is the remaining percentage of rated power. The cards show the effective system size, year-10 output, lifetime energy and energy lost, and the chart shows output year by year.
Solar panel degradation formula
Panel warranties use a linear model: a larger drop in the first year, then a steady loss every year after.
Where:
- P(n) is output in year n as a fraction of rated power.
- LID is the first-year loss, mostly light-induced degradation, as a decimal.
- d is the annual degradation rate after year 1.
- Enew is the yearly energy the system would make with no degradation.
- N is the number of years, 25 or 30.
Warranties are a floor, not a forecast. In NREL’s analytical review of nearly 2,000 measured degradation rates, the median was 0.5% per year, and newer panels generally do better than that.
Worked examples
Example 1: TOPCon panels over 30 years
1% first-year loss, 0.40% a year after that:
An 8 kW array performs like a 6.99 kW array in year 30. With 11,000 kWh a year when new, the yearly fractions add up to 27.96, so:
That is 22,440 kWh less than a panel that never aged.
Example 2: mono PERC panels over 25 years
2% first-year loss, then 0.55% a year:
The 25-year sum is 22.85, so the same 8 kW system makes 251,350 kWh, and loses 23,650 kWh to degradation.
Example 3: back-contact panels over 30 years
2% first-year loss, then 0.25% a year:
Lifetime energy is 311,438 kWh, about 3,900 kWh more than the TOPCon profile over 30 years.
Solar panel degradation by year
Remaining output in percent of rated power, computed from each warranty profile. 30-year energy assumes 11,000 kWh a year when new.
| Profile | Year 1 | Year 5 | Year 10 | Year 15 | Year 20 | Year 25 | Year 30 | 30-year kWh |
|---|---|---|---|---|---|---|---|---|
| N-type TOPCon (1% + 0.40%/yr) | 99.0 | 97.4 | 95.4 | 93.4 | 91.4 | 89.4 | 87.4 | 307,560 |
| Mono PERC (2% + 0.55%/yr) | 98.0 | 95.8 | 93.0 | 90.3 | 87.5 | 84.8 | 82.0 | 297,082 |
| Premium PERC (2% + 0.50%/yr) | 98.0 | 96.0 | 93.5 | 91.0 | 88.5 | 86.0 | 83.5 | 299,475 |
| Back contact (2% + 0.25%/yr) | 98.0 | 97.0 | 95.8 | 94.5 | 93.2 | 92.0 | 90.8 | 311,438 |
| Field median (0.5%/yr) | 99.5 | 97.5 | 95.0 | 92.5 | 90.0 | 87.5 | 85.0 | 304,425 |
The profiles come from current datasheets, checked October 2026: Jinko Tiger Neo (87.4% at 30 years), Trina Vertex S DE09R (84.8% at 25 years), Qcells Q.PEAK DUO (86% at 25 years) and Maxeon (92% at 25 years). PERC values past year 25 extend the same line beyond the warranty.
What affects solar panel degradation
Cell technology
P-type PERC cells suffer more light-induced and light- and elevated-temperature-induced degradation, which is why their warranties allow 2% in year 1. N-type TOPCon and heterojunction cells are far less affected, so warranties allow only about 1%.
Heat
Degradation runs faster in hot climates. Panels on dark, poorly ventilated roofs in places like Arizona or Texas often age faster than the same panels in a cool climate. Hot cells also produce less power right now, which the solar panel temperature loss calculator shows.
Potential-induced degradation
High string voltage can pull ions through the glass and damage cells, a problem called PID. Modern panels are tested for PID resistance, and inverter grounding choices also matter.
Physical damage
Micro-cracks from rough handling, hail or snow loads can cut output in parts of a panel over time. Proper handling and installation matter as much as the panel’s chemistry.
Frequently asked questions
How much do solar panels degrade per year?
Most panels lose 0.25% to 0.55% a year after the first year, with a larger 1% to 2% drop in year 1. NREL’s review of nearly 2,000 measured rates found a median of 0.5% a year. Modern n-type panels are usually warranted at 0.40% a year or better.
How much power will my solar panels have after 25 years?
Under warranty terms, 85% to 92% of the original rating, depending on the panel. A PERC panel at 2% plus 0.55% a year keeps 84.8%, a TOPCon panel about 89.4% and a back-contact panel 92%. Many real panels beat their warranty line.
What is LID in solar panels?
LID stands for light-induced degradation, a quick loss of power when a new panel is first exposed to sunlight. It mainly affects p-type cells and is mostly over within weeks. Warranties cover it by allowing a larger loss in year 1, typically 2% for PERC and 1% for n-type panels.
Does degradation affect solar payback?
A little. At 0.4% to 0.55% a year, a system makes 7% to 10% less energy over 30 years than one that never aged. Rising electricity prices often offset that. Include it when comparing panels, and use the solar payback calculator for the full financial picture.
How do I claim a solar panel power warranty?
You need proof that output is below the warranted line, usually from a flash test or field measurement that accounts for temperature and irradiance. Monitoring data showing a steady drop helps you spot it. Contact your installer first; they usually handle the claim with the manufacturer.