A general, demand-driven, numerical simulation model for thermal analysis of ground-loop heat exchangers (TAGLEX) is given for residential heat pump systems. The model is built from component modules, which are linked together to form a system. These modules include, among others, ground coupling of a pebble bed, a surface tank, a vertical well closed loop, and a horizontal pipe system. The transient two-dimensional heat conduction equation; which is used to calculate the temperature fields surrounding the ground-coupled heat exchanger, is solved for many slices along the length of the heat exchanger by an explicit finite difference formulation. The predicted seasonal COefficients of performance for heating and cooling are compared with previously reported experimental results for the same systems. The predictions are found to be in good agreement with the experimental results.