But what happens after that, when the warranty language is long gone and you are still hoping your roof system keeps shrinking the electric bill?.
A new analysis led by Ebrar Özkalay at the University of Applied Sciences and Arts of Southern Switzerland suggests the answer can be surprisingly good.
The scientists examined six grid-connected solar systems installed between 1987 and 1993 across different Swiss regions, from lower elevations to alpine sites.
They combined decades of performance monitoring with lab tests on selected modules to see how output changed and what physical wear looked like inside the panels.
One key metric was the performance loss rate, which is basically how much power a system loses year by year as it ages.
Across the six sites, the average annual loss was about a quarter of a percent, far lower than the range often cited in earlier field studies.
In this case, the study found clear differences tied to material quality, even within the same module family. »