sperry wrote:Some mention a cooling effect in room also?
As the name implies it "pumps" heat, they move heat from one location to another which is also what an air conditioner does. Heat pumps for houses source their heat from outside air, as the temperature drops they become less efficient.
The heat pump on hot water heater uses indoor air, the source of your heat is your primary heating source hence the reason it's going to make the room colder. This is fantastic if you live in a warm climate or during the summer and want to remove heat from that living space. The efficiency of these are based on regular electric, if they are saying it's 200% efficient it's going to use half the electric of standard. What is not included in this is the heat that it stole from primary heating source.
Let's suppose you have electric heat, you put 2000 BTU's into the air and then the heat pump uses 1000 BTU's of electric for mechanical energy to move it to the water heater for total of 3000 BTU's. I'm unclear exactly where that 1000 BTU's of energy used for the mechanical energy goes. Some of it for example will turn to heat because of friction and be put back into the room.
I have topic on that here: Pressure and AC/Heat pumps
I don't see how this can ever be as efficient as directly heating the water with 2000 BTU's in regular electric water heater. There is caveat here, you have a primary heating source that is far lower cost per BTU than electric. Even if the energy use increases the costs will probably be lower over standard electric since you are basically using coal to heat the water. Of course the dehumidifying costs you avoid should also be considered but how much does your dehumidifier run?