GetSunScore Analysis: Solar Degradation Rate
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 affects lifetime production. GetSunScore applies documented scenario assumptions to its 20-year estimates, without predicting how a particular panel will age.
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.
Degradation is often illustrated as an annual percentage reduction in output. Under a purely illustrative 0.5% yearly reduction, 400W of starting output would become about 362W after 20 reductions. Actual panels need not follow a constant rate.
Why Degradation Matters in Modeling
The calculator begins with the selected city's annual PVWatts yield and adjusts modeled production downward between years according to the scenario's annual degradation assumption.
Lower modeled lifetime production generally lowers cumulative electricity value and can lengthen modeled payback. The assumptions are sensitivity choices; see the methodology rather than treating them as current product-warranty data.
How Degradation Applies in Texas
Texas site conditions, equipment, installation, and maintenance can affect actual output over time. The screening estimate does not assess these property-specific factors.
Review the equipment warranty and a site-specific proposal when evaluating a real installation; the modeled degradation scenarios are not warranty terms.
Frequently Asked Questions
Solar degradation is the gradual decline in a system's output over time. The rate varies by equipment and conditions. As an illustration, applying a constant 0.5% annual decline to a 400W starting output gives about 362W after 20 reductions; it is not a product forecast.
The current calculator starts with a committed PVWatts annual city yield and reduces modeled production each subsequent year using the selected scenario's degradation assumption. This affects its 20-year savings and payback estimates.
Heat and other site conditions can affect actual equipment performance. GetSunScore does not model a specific roof, panel warranty, or local degradation rate; its scenarios use documented sensitivity assumptions.
The calculator uses different annual degradation assumptions in its low, base, and high scenarios. The current values are shown on the methodology page; they are model choices, not a prediction for a specific panel.
Lower lifetime output can raise a separately calculated LCOE. GetSunScore's current calculator does not report LCOE; it uses degradation when estimating long-term production, savings, and payback.
The calculator's degradation rates are documented scenario assumptions, not a 2024 product dataset or a guarantee of future output.