Panel companies are only comfortable offering this guarantee because of a 2012 nrel study photovoltaic degradation rates an analytical review that found solar panels degrade about 0 5 to 3 each year barring any equipment issues.
Degradation rate of solar panels.
Most solar panels last 25 years with an average annual degradation rate of 50.
Solar panels do not go bad and very rarely are they faulty or break.
The different independent studies that tackled the question of solar modules degradation end up with an average of 0 8 per year.
This can be measured and recorded using a photovoltaic production meter.
As an example let s assume the following about our solar system.
Most solar installers build into contracts an expected photovoltaic efficiency degradation rate that typically doesn t exceed 20 over the contract s term.
Degradation at a rate of 0 25 to 0 4 per year ensures that your solar power system continues to produce more than 90 of its original power production for 25 years.
Solar inverters and solar batteries will need replacing within the 25 year solar panel lifespan.
So panels degrade automatically.
Degradation is defined as the loss of power produced relative to the rated power.
According to an analysis by the national renewable energy laboratory nrel some premium panel manufacturers offer degradation rates as low as 0 3 per year.
For monocrystalline silicon the most commonly used panel for commercial and residential pv the degradation rate is less than 0 5 for panels made before 2000 and less than 0 4 for panels made after 2000.
But with degradation of 0 8 per year production drops below 90 before 15 years have passed.
Solar panel degradation rates are constantly improving as solar panel technology gets better over the years and degradation rates below 1 are common throughout the industry.
Though this rate of decline metric will vary depending on which panel brand you buy premium manufacturers like sunpower offer degradation rates as low as 0 3.
However a study conducted by the national renewable energy laboratory nrel shows a more accurate picture of solar panel degradation.
That s worked into their performance warranties.
To calculate the annual degradation percentage of solar panels we ll need to know the annual kwh production of the system.
That means that a panel manufactured today should produce 92 of its original power after 20 years quite a bit higher than the 80 estimated by the 1 rule.
That s backed up by the solar panel manufacturer s warranty which guarantees 90 production in the first ten years and 80 by year 25 or 30.
And while other brands have higher degradation rates of up to 0 8 per year that s still a yearly average degradation rate of only 0 5.
