In recent years, increasing attention has been paid to the use of renewable energy sources in building sector. The ground source heat pumps are a promising alternative for heating and cooling applications. Despite the high coefficients of performance and significant environmental benefits, their performance may deteriorate over the long-term operation if the annual ground loads are not well balanced. An appropriate solution is the use of hybrid ground source heat pump system through which some portion of the thermal loads can be offset by supplemental components. The aim of this study is to assess the feasibility of a solar-assisted ground source heat pump system for heating a detached house in a cold climate of northwestern Iran. The economic and environmental aspects of the proposed hybrid system are compared with those of a ground source heat pump, an air source heat pump, and a natural gas space heater for a 20-year design life. The analyses show that despite having high initial cost, the hybrid system has the second lowest life cycle cost and the lowest carbon dioxide emissions. © 2018 Islamic Azad University (IAU)