The utility model discloses an energy -efficient air can water heater, include through refrigerant pipeline circulating connection's evaporimeter, compressor, condenser, filter and expansion valve, still include: water tank, its upper end are equipped with the hot water outlet pipe, and the lower extreme is equipped with cold water inlet tube, refrigerant entry, and cold water inlet tube upper endintercommunication has spherical portion, cold water inlet tube overcoat is equipped with first sleeve, and first sleeve overcoat is equipped with the second sleeve, a plurality of baffles, it has all seted up the arc hole with the inside a plurality of spaces of share of water tank on every baffle, the condenser pipe, it passes a plurality of baffles by down supreme, and the part that the condenser pipe is located every space all communicates has first branch pipe, and a plurality of first branch pipes all communicate the second branch pipe outside being located the water tank. The utility model discloses a water heater, the velocity of flow of offering messenger's cold water entering water tank in a plurality of water conservancy diversion holes through spherical portion, first sleeve,second sleeve outward can reduce to reduce in the water tank mixing velocity of original hot water and cold water, improved hot water utilization ratio.