Definition and Solar Context
Solar degradation rate is the annual percentage reduction in the electricity output of a photovoltaic (PV) solar panel over time due to physical and chemical changes in the panel materials. All solar panels lose a small amount of generating capacity each year.
Degradation rate is a key variable in 20-year solar savings modeling because it affects total lifetime energy production. GetSunScore incorporates industry-standard degradation rate assumptions into the SunScore™ Projection Engine.
What Does Degradation Rate Mean?
Solar panel degradation refers to the gradual reduction in a photovoltaic module's power output over its operational lifespan. This decline results from several mechanisms including light-induced degradation (LID) and thermal cycling effects.
Industry-standard degradation rates for crystalline silicon panels Typically range from 0.5% to 0.8% per year. A panel rated at 400W at installation would, under a 0.5% annual degradation assumption, produce approximately 361W in year 20.
Why Degradation Matters in Modeling
Degradation rate is a compounding variable in 20-year projection modeling. The SunScore™ Projection Engine applies an annual degradation factor to the production estimates in each modeled year, resulting in a declining production curve.
The cumulative effect of degradation reduces total estimated lifetime energy production compared to a flat production assumption. A higher degradation rate extends the modeled payback period. GetSunScore uses benchmarks consistent with current NREL research.
How Degradation Applies in Texas
Texas climate conditions are relevant to solar panel degradation analysis. High ambient temperatures throughout Texas summers can accelerate certain degradation mechanisms, including thermal cycling effects.
Most modern panel manufacturers account for temperature-related degradation in their published performance warranties. The SunScore™ Projection Engine applyies crystalline silicon benchmarks as the most applicable standard for the Texas residential market.
Frequently Asked Questions
Solar panel degradation is the annual reduction in a panel's electricity output over time. Most modern crystalline silicon panels degrade at approximately 0.5% per year, meaning a panel producing 400W at installation might produce approximately 361W after 20 years.
The SunScore™ Projection Engine applies an annual degradation factor to modeled production estimates for each year of the 20-year projection. This produces a declining production curve that provides a more realistic estimated savings range.
High ambient temperatures can contribute to certain degradation mechanisms. However, modern panels are engineered to tolerate Texas climate conditions. GetSunScore applies standard industry degradation assumptions sourced from publicly available NREL research.
GetSunScore applies a reference degradation rate consistent with NREL-published benchmarks for crystalline silicon panels. Specific modeling assumptions are disclosed on the /methodology and /assumptions pages.
Solar degradation rate directly affects the Levelized Cost of Energy (LCOE) calculation. As output declines over time, the effective cost per kilowatt-hour produced increases. See the LCOE glossary entry for a detailed explanation.
All degradation rate inputs are applied as modeled assumptions based on publicly available industry research (reference year: 2024). Actual degradation rates vary by manufacturer.