Abstract: A geothermal heat pump system which may be installed in a building and operated as an air source heat pump system using an exterior heat exchanger as a heat source or heat source/sink, but which includes geothermal components including a geothermal heat exchanger. The geothermal heat exchanger may be isolated in initial operation of the system for heating and cooling but may be connected to a geothermal heat source/sink following initial installation of the heat pump system for use in heating and cooling as a heat source and a heat source/sink, respectively. In this manner, the heat pump system may be initially operated as a standard air source heat pump and optionally later converted into a geothermal heat pump system.