I am fairly well versed in Physics ,math, , Science etc. I understand that the efficiency basically comes from the relatively stable temperature of groundwater and good efficiency of actual heat transfer. What I want to address is : If I have a 5 ton heat pump air conditioner in cooling mode and a 5 ton geothermal unit both running at full capacity ( in say 90 degree outside temp ) is the geothermal compressor using the same amount of electricity (not multistage or inverter type). I would assume it does unless rated in tons of conditioned air and not compressor size. Is the savings due to colder air output for the geothermal than the air source unit thus allowing the geothermal to run a smaller amount of time to cool same amount of BTU s ? I am not considering the well or circulation pump to get the water to the geothermal unit or fan etc, just the compressor.

It depends on the loop water temperature. If you are open loop and for example have 60F loop water temperature, then the geothermal unit compressor will be pulling less amps than a conventional air source heat pump compressor working in 90F air. The geo unit compressor will have lower high side hot refrigerant pressure because of the 60F cooling water and therefore will not be working as hard as the air source heat pump compressor trying to reject heat into 90F ambient air. Less work = less amps drawn.

Plus, a geo unit with lower temperature loop water will produce more BTUs than a geo unit with higher temperature loop water (this info is published in the manufacturer's literature). The same comparison can be made to an air source heat pump operating in A/C mode in cool vs. high ambient temperature. Cooler heat sink = Higher BTU output = shorter run time = less energy consumed.

Thanks for reply. I understand that . Didnt think about different compressor temp/pressure.