A combined water heating, space heating and space cooling system configured to provide hot water to a point of demand and heat or cool a space. The system comprises a heat pump operably connected to the space, a water flow loop including a main heat exchanger, a fluid mover for moving a fluid configured to flow within the flow loop, an air-to-water heat exchanger, a burner adapted to heat the fluid, a blower having an air inlet end and an air outlet end, wherein the blower is adapted to move air through the air-to-water heat exchanger and operably connected to the main heat exchanger and a secondary heat exchanger operably connecting the flow loop and the heat pump. The air-to-water heat exchanger is disposed on the air inlet end and the main heat exchanger is disposed on the air outlet end.