Heat exchange rate, water-to-earth, in a closed loop vertical bore configuration was measured. Thermal conductance with a vertical steel casing and PVC plastic inner return pipe was found to be 4.86 W/C/m (2.81 Btu/h F/ft) for 100% on-time, 7.51 W/C/m (4.34) for 50% on-time and 11.89 (6.87) for 25% on-time. A polyethylene side-by-side U-bend heat exchanger had conductance values of 3.46 (2.00), 4.71 (2.72), and 11.60 (6.70) for 100, 50, and 25% on-times, respectively. Energy and efficiency parameter relations for sizing a heat exchanger are given and explained with an example problem