Solar panels installed in France in 1992 were found to retain a remarkable 79% of their original power

Why is it important: Solar panels are designed to last for decades, with an estimated lifespan of 20 to 40 years. However, their efficiency and ability to produce energy will deteriorate over time. Surprisingly, a new long-term test conducted in France gives a positive picture of the durability of solar panels in the natural environment.

In 1992, a small 1-kilowatt solar panel called Phébus 1 was connected to the French grid by Hespul, a nonprofit renewable energy association based in Lyon, France. More than 30 years later, the same installation still produces cotton wool. After dismantling the 10-square-meter historic plaque last year, technicians subjected the panels to rigorous laboratory tests in line with international standards and achieved astonishing results.

After 31 years of operation, it was still achieving an average of 79.5 percent of its initial rated power. Solar panel manufacturers typically only guarantee 80 percent of original efficiency for up to 25 years. Phébus 1 exceeded this rate, with declines averaging just 0.66 percent per year over its 31-year existence.

For example, in 2012, the 20th anniversary of the installation, the panels still achieved 91.7% of their rated power. In the case of some modules, this decline has accelerated slightly in recent years. After 31 years, the modules produced 20,366 kWh at 882 Wp, or 745 kWh/kWp/year.

“These results confirm the results of various scientific studies that provide references on this topic,” concludes Hespul.

The association cites a long-term Swiss study and the latest American and European studies, which showed that the average degradation rate of solar panels ranges from 0.36 to 0.75 percent per year. So, while declines in production are inevitable as the years go by, this real-world data shows that solar PV installations can operate for several decades while maintaining very cost-effective levels of efficiency.

This durability bodes well for residential roof panels and the overall shift to cleaner sources of electricity generation.

A report by Ember, an independent global energy think tank, also contains positive news on this issue. The latest report from the Global Electricity Review shows that renewable sources such as solar and wind energy reached new records in 2023 and accounted for more than a third of global electricity production. Solar power saw 23 percent year-over-year growth, while wind power grew 10 percent.