Blake, thanks for the info. I considered SWC with an abandoned well but did not pursue it because, 1) there is less info about making it work verses a closed system; 2) pumping power required; 3) quality of water here. A few questions: Your $121 electric bill - was that your whole house or your heating submetered? What are you charged per kwatt? Pumping is 1.5 amps - so 360 watts? What controller(s) do you use to achieve that? How low does your EWT get? The water quality problem I faced was that the well gets a lot of slime and was concerned it might plug any filtering. Also, the slime is made from a bacteria that generates methane and hydrogen sulfide. These gases interfere with any sort of vacuum that would be in the discharge line unless system was run with higher pressures - which would drive up pumping costs. Otherwise, from a mineral standpoint, nothing is corrosive or causes buildup. I settle with a closed vertical loop, 1.5" pipe, ungrouted well. EWT is ~40 during heaving heating demand (much of this winter). Pumping is 197 watts.