Heat pump deserves the name of eco-innovation. It uses ‘free energy’ - warmth collected in the soil or in the air to provide heat ing and cooling. There are two main types of heat pumps – air source heat pump and ground source heat pump. How do they work? What are the benefits of each system? How do they compare? First of all, questions like “what is heat pump, how does it work, what are ASHPs and GSHPs” will be answered. Then a detailed comparison between ASHPs and GSHPs will be carried out, from technological parameters to social, practical, economical parameters. Finally, the conclusions are drawn from these parameters as to decide which kind of heat pump is better off under different conditions.