Buildings get torn down. Roof needs a replacement and the owner doesn't feel like it is worthwhile to redo the solar install for panels that only have 5 years of warranty left, or maybe they want to replace them with higher power models with a fresh warranty. There are any number of reasons why someone might need to offload otherwise functional solar panels.
Currently used solar panels are a hot commodity, with many groups selling them by the pallet, because 10 year old solar panels are still efficient enough to easily pay for themselves. Very few installations will care about specifically how many panels they want, they just want a nameplate output per dollar figure.
Old inverters might not have a second life though.
In Ontario, there is a feed-in-tariff program for payment in exchange for renewable/green energy generation direct-to-grid. This program has contracts which expire. The microFIT program (under 10kW/hr solar capacity) has a bulk of contracts expire around the same short period of time.
There is not-yet a fully funded or thought-through method for extending contracts or providing better-than-dismantle options to contract owners that is/are accessible.
