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Solar modules deployed in France in 1992 still provide 75.9% of original output power
(www.pv-magazine.com)
This is a most excellent place for technology news and articles.
As far as I know that's nothing to write home about, monocrystaline solar panels get like ~30 years dropping down to 80% and then slowly begin to fail from there. I'm far from an expert, but my understanding is this is the norm and that if we found out they weren't lasting this long then people would be getting worried about a messed up cost calculous.
That's correct, but most of those calculations were based on theoretical figures used by artificial aging methods and computed failure rates. Now we have real world data from panels that actually aged that long.