I have a 5 ton in a 3500 sq. ft. with 32 windows, 5 exterior doors, 2000 sqft basement, on top of a hill in flat country. My electric bill has hovered around $160 the past six months. I installed the bottom diffuser aerator against the my Mfg. recommendations and have seen no unexpected bill increases except for the $30/mo for my aerator that runs 24/7. All I have to worry about is blowing out the reusable air filter every month or so. My geo system only cost $1100 more than a standard Electric furnace and heat pump. A well based pump and dump would have cost more in my case because they would have had to drill larger and deeper well.
As far as effeciency of dump vs. recirc., from what I've read it can go either way by 10% or so depending on air temp, groundwater temp, and how many ft of head you have to pump the water. In a closed loop you're probably looking at running a 1/3 hp recirculator vs. the 1.5 hp well pump, smaller is cheaper to replace if needed. In the past, recirculating components have outlived pump and dump components because of iron and other minerals causing parts to wear out.
A pump and dump system opens you up for more excuses, such as component wear due to water quality issues, for a manufacturer not to warranty their product compared to a sealed system. If you need the water to keep your pond filled then the pump and dump may be your only option obviously because a closed loop in the bottom of a dry pond isn't going to help much.
I've read about people switching from pump and dump to closed loop due to problems but never the other way around.
Supercooling? I have never heard of this actually happening with any residential system.
Dumped heat heats my water. You may have to request that be hooked up.
