Not enough to prior art, the utility model aims to solve the technical problem that: the utility model provides a kitchen water heater carries out the coupling with a working medium circulation system and kitchen discharged waste gas system and wastewater systems, and wherein working medium circulation system and waste gas system are in the coupling of waste gas evaporimeter department, locate the coupling with wastewater systems at useless water evaporator. Partly running water earlier after partly heat of kitchen waste discharge is retrieved to the pre -heater, gets into and supplies water condenser, by working medium circulation system's condenser coil to supplying the water among the water condenser to heat, the warm water that supplies water supply that water condenser came out and a part of running water that does not heat in addition to coordinate into the desired temperature under the effect that mixes the water valve supplies the kitchen operation to use. This kitchen water heater has simple structure, thereby energy -conserving effect is showing, is saving space, is realizing advantages such as water and electricity separation factor of safety height very much.