This paper presents a tool for computing thermal resistance of single U-tube ground heat exchangers placed in vertical boreholes. The tool is complete in the sense that it can compute both local and effective thermal resistances for either grouted or groundwater-filled boreholes. For grouted boreholes, it utilizes the highly accurate multipole method. For groundwater-filled boreholes, it utilizes recently-published convection correlations. Thermal property routines for water and water-antifreeze mixtures allow calculation of the interior convective thermal resistance for a wide range of cases
