Used gas furnaces are found on eBay and Craigslist, as of 2015. Both sites allow buyers to search in a preferred geographical area, as shipping a furnace may be expensive. A person may also find one in a local newspaper.
Though buying a used furnace may seem like an affordable option, consumers should be aware that it could cost them much more over the next several years to run a used furnace as opposed to an old one. For the most part, new furnaces are much more efficient than old ones. Used furnaces may also incur higher installation and labor costs compared to new furnaces, which sometimes have installation services included with the purchase price.