The thing to note is that heat pumps move heat energy, they don't generate it (other than as losses from the machinery). Your fridge moves heat energy from insi

The thing to note is that heat pumps move heat energy, they don't generate it (other than as losses from the machinery). Your fridge moves heat energy from inside itself to the outside, leaving the insides cool. A heat pump moves heat energy from outside the house to inside of it, leaving the outside cooler. This allows it to be 3-4 times more efficient than resistive heating (which does generate heat energy), because it just moves energy around. This heat pump will also have to move the heat energy from somewhere. It can't do that if there's none to begin with.