I have seen water heat pump systems. They are meant to replace boilers for radiators or under floor heating. Then the hot water can be stored. Or go to a heat e

I have seen water heat pump systems. They are meant to replace boilers for radiators or under floor heating. Then the hot water can be stored. Or go to a heat exchanger for heating and cooling with ducts. Water is much easier fluid to work with than refrigerant. One reason don't see combined systems is that refrigerator and water heater don't move that much heat. Refrigerator is fine dumping the heat into the kitchen, and water heater pulling heat from the basement. The air inside the house turns into the working fluid.