Solar panels installed in France in 1992 retain 79% of their original output, 31 years later

The usual lifespan of solar panels is estimated to be between 20 and 40 years, with efficiency and power generation degrading over time. However, installation in France from 1992 is still pumping away with 79% of their output.

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Technicians dismantled the vintage 10-square-meter 1-kilowatt solar array last year, running the solar panels through rigorous lab testing per international standards and finding impressive results. Even after 31 years of service, an average of 79.5% of the initial rated power output is achieved.

Solar panel manufacturers usually guarantee around 80% of their original performance for up to 25 years, but the "Phébus 1" solar system has been running for 31 years and counting, with an average annual decline of just 0.66%. The solar system celebrated its 20th anniversary of installation back in 2012, with the panels pumping 91.7% of their rated output, but with the years clicking away the drop-off in efficiency has increased on particular modules.

After 31 years, the solar modules have produced 20,366 kWh for 882 Wp, or 745 kWh/kWp/year, not bad at all.

The 1-kilowatt solar system is connected to the French grid company Hespul, which says that "these results confirm those of various scientific studies that are references on the subject."

Hespul says a long-term study by the Swiss and recent American and European research shows median solar panel degradation rates from 0.36 to 0.75% annually. These declines in output will happen, but the massive real-world data shows solar installations can keep providing energy for decades... while keeping highly viable performance levels.

Another thing to consider is that these are extremely old solar panels... and technology has improved by leaps and bounds by then, so it'll be interesting to see how solar systems of today hold up in 10, 20, and 30 years from now.