The aim of this research is to study the mass flow rate and inlet water temperature effect of hot water that fed to evaporator section of the boosted heat pump comparing the case study of using air source. Both heat pumps were test under the hot water temperature condition of 35-65 ^oC that produced hot water of 100 liter storage tank. For methodology, the boosted heat pump was adapted with the water box installed at the evaporator section and the variation of hot water temperature was controlled by the electric heater and then fed the hot water into the evaporator section at the mass flow rate of 1 kg/min, 2 kg/min, and 3 kg/min under the inlet temperature variation of 35 ^oC, 40 ^oC, 45 ^oC, 50 ^oC, 55 ^oC, 60 ^oC, and 65 ^oC, respectively. While the conventional heat pump, the fan blown the ambient air into evaporator section. The coefficient of performance (COP) of both heat pumps were calculated and it was found COP of the boosted heat pump was higher than the conventional heat pump at every the mass flow rate, moreover, COP would be decreased when the water temperature in storage tank increased because the power of heat pump increased. The suitable of mass flow rate was clearly at 2 kg/min and the hot water temperature that fed to the evaporation section of boosted heat pump was equal to 45 ^oC. COP of boosted heat pump could be raise the highest value of 3.69 while COP of conventional heat pump was equal to 2.51.