Compares the results of five practical vertical ground heat exchanger sizing programs against a detailed simulation model calibrated to monitored data taken from one family house. The calibration of the detailed model to data is described in a companion paper. States the results of the comparisons demonstrate the current level of agreement between vertical ground heat exchanger sizing methods in common use. Recommends that the calibration and comparison exercise be repeated with data sets from additional sites in order to build confidence in the practical sizing methods.Units: DualKEYWORDS: year 1997, Heat exchangers, soil heat exchangers, vertical, heat pumps, soil heat pumps, housing, USA, sizing, comparing, computer programs, calibrating