Hydronic heating professionals often promote the concept that current generation mod/con boilers can operate with AFUEs in the range of 95% and above. Professionals who install geothermal water-to-water heat pumps often boast their equipment is capable of coefficients of performance (COPs) in the range of 3.0 to perhaps 3.5. These performance numbers are possible given the right equipment, the right application and a specific definition for thermal efficiency and COP used when evaluating the equipment.
However, most of these same hydronic pros don’t bother to describe how a well-designed and properly installed hydronic heating system has a distribution efficiency much higher than that of either a forced air system or a system that moves heat through a building using refrigerant.