The federal tax incentives as well as my local utility production based incentives(an additional 8 cents per kwh for 10 years) required that I installed new panels.
How much cheaper would you expect used panels to be? I've never come across standard 60 cell panels at a price on craigslist or ebay that I thought was a decent price compared to buying new when the additional shipping costs of ebay were involved and the loss of the incentives were gone and craigslist always had old lower efficiency panels, damaged panels, or a quantity that was either way too many or not enough.
If I was off-grid or incentives were not a factor, I'd likely go used if the price were dirt cheap, the panels were in decent shape, and the quantity was right for the application.
..but even then I've liked the idea of taking some of the 90ish cell panels and connecting them directly to used LiFePO4 cells with enough to suit standard 48v inverters and build in a simple system that cuts charging at max cell voltage and skip the BMS and MPPT(have the panels and number of cells configured for an panel MPPT match at 3.4v per cell which is pretty much where the charging voltage sits from like 50%-90% SOC. It would be dirt cheap off-grid without the short life of lead-acid..
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