Looking at six solar arrays in Switzerland that have been running since the late 1980s and early 1990s, the team found most panels still produced more than 80% of their original power after three decades.

Temperature turned out to be a major character in the story. The study reports that lower-altitude systems faced higher thermal stress, with module temperatures reaching about 20 degrees Celsius warmer than high-altitude sites, and those hotter panels tended to degrade faster.

Some of the wear mechanisms were very specific but easy to picture. The encapsulant, the clear plastic layer that helps protect and hold the solar cells, showed more breakdown in hotter conditions, and the researchers linked that to chemical byproducts that can contribute to corrosion over time.

I wonder if new panels last even better, since there’s been more R&D done and manufacturers should have more experience now