This got me thinking again. Panel life/degradation figures put about by installers/manufacturers might be 'spun' to tell a good story, so I looked for independent research. The NREL in the USA has published some data.
This chart is perhaps the most interesting - median degradation is 0.5% pa, mean is 0.8% because there are some 'bad ones' out there.
https://www.nrel.gov/pv/assets/images/p ... phic_8.jpg
The normal quoted life is 20 years at which point they should still be at least 80% efficient. Extrapolating the chart and compounding over 20 years, one with median 0.5% degradation would be 90.9% efficient after 20 years, the worst (I've used 3.8% from the right hand side of the chart) would be only 47.8% efficient - a real difference.
I guess all salesmen (sorry, "green energy consultants") will say theirs is the best, but how does the buyer know what they are getting?
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