Abstract The aim of this study is to evaluate the effect of a superheating and sub-cooling heat exchanger (SHCHE) to the performance of ground source heat pump system for climatic condition of Erzurum having cold climate in Turkey. For this purpose, an experimental set-up was constructed. The experimental apparatus consists of a series ground heat exchanger (GHE), a liquid-to-liquid vapor compression heat pump, water circulating pumps and other measurement equipments. In this study, the performance of the systems with and without SHCHE was experimentally investigated. The experiments were performed in 2010 for January and February which are the coldest months of the heating season. The experimentally obtained results were used to calculate the power values of the main system equipments, the coefficient of performance of the heat pump (COP) and the overall system (COPS) for systems with and without SHCHE.