With so many homeowners and businesses considering the installation of a solar power system, it’s only natural to wonder – how long do solar panels last? Solar panels typically are marketed with twenty-year warranties that guarantee at least 80% of their rated power production up to 20 years of usage. From this, it can be seen that the guarantee is based on the fact that a 1% annual reduction in efficiency will occur, so that by the expiration of the warranty, there will have been a 20% loss in efficiency of energy production.
NREL Analysis of Solar Panel Longevity
The above scenario has been exhaustively analyzed by the National Renewable Energy Laboratory (NREL), which has conducted a whole series of studies that examined the long-term degradation rates of many different types of solar panels. Their findings indicated that the 1% rule used as the basis of most warranties was actually rather pessimistic.
When analyzing the efficiency of panels manufactured before the year 2000, the typical rate of degradation was found to be only about .5%, whereas more efficient panels manufactured after the year 2000 were found to have retained at least 92% of their original rated power, even after 20 years of usage.
In other words, the rate of degradation for modern solar panels is minimal even after decades of usage, so the effective life of solar panels made with modern technology can be assumed to span as much as 40 or 50 years. With even modest improvements of technology in the coming years, it is safe to assume that, for all intents and purposes, solar panels will last indefinitely.
Degradation in solar panels
When degradation does occur in solar panels, it is most frequently attributable to the abuse sustained by panels in very cold or very hot climates. Where heavy wind and snow loads can occur, it affects the silicon module components of solar panels, and in climates where desert conditions are prevalent, solar panels showed large decreases in production – even greater than the 1% rate – due to high exposure to ultraviolet sunlight.
Solar panels used in moderate climates, for instance the northeastern United States, were found to have very low rates of degradation over time, typically in the range of .1% to .2%, which puts them very close to relative permanence.
The degradation rates determined by the NREL are now commonly used in assessing potential solar sites in order to estimate energy production over the lifetime of any given solar power system. Using the analysis provided by an NREL, and adjusting it to account for the section of the country or the section of the world where a solar power system will be installed, it can be a fairly easy process to determine the lifespan of solar panels, and how long they can be expected to produce energy at their rated value.