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Old 05-16-19, 10:07 PM   #7
WisJim
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My oldest panels (installed in 1982) are Arco 35 watt, and I'm sure there is deterioration but I can't accurately measure it even with good Fluke meters due to sunlight variation. I also have some 85 watt Solavolt that are about 25 years old, same thing. Then is an array of 125 watt Kyocera panels that are 15 years old and the occassional maximum power output is within a few watts of my readings when they were new. And the newest arrays are Evergreen, purchased when panels finally dropped under $1/watt--and they usually produce 5% more power than their rated output during some cold sunny March days, since we installed them in 2012--no noticable power loss yet.
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