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Posts: 25
Reply with quote  #1 
I have found a local source of PV panels that have been used for 6 years. I have read that PV panel performance drops over time. Is that true? How significant is the drop? My thinking is that if they are cheap enough I can just add more panels to offset the loss in output. Is that correct? Would you consider 6 year old panels?

If I do buy some panels, what should I check when I collect them?
How should I estimate the dollar value of used panels compared to new panels?


Posts: 101
Reply with quote  #2 
Yes panel operation will degrade over time. Most quality panels have a guaranteed 25 year life of at least 80% output after the 25 years are up. For buying used panels I would check the short circuit current. Short the two leads together and measure the current in full sun using an amp clamp. See if it is close to the rating listed on the panel. Also test the open circuit voltage to see that it is close to the panel rating. Physically inspect the panels for damage. If the coating on the back side is torn then that becomes a source of water damage when it is wet outside. Not good.
Personally I would no longer pay more than 50 cents per watt as new, warrantied panels can be purchased for that price regularly now. Of course that could depend on where you live and if shipping is involved.

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