I'm a little puzzled by the concept here. The water heater partially heats the water by drawing heat from the surrounding air. That will make the surrounding air cooler. If the heater is located inside the house, then it is acting like an air conditioner in whatever space it is installed in. That's fine in the summer when the cooling effect will supplement the home A/C system but in the winter, the primary heating system will have to replace the heat energy consumed by the water heater. If the home is heated with electrical resistance heating, there will be no net energy saving in the winter. If the home is heated with a heat pump, natural gas, or oil, the savings will be the difference between the cost of electrically heating the water (standard water tank) and the cost of providing the same amount of heat energy by the primary heating system. This system would probably make the most sense in a hot climate like Florida and the least sense in a cold climate like Alaska!