Heat pumps are typically 200-400% efficient. That is, they move 2-4x as much heat as they produce to move that heat. Although that is usually radiating energy to a fairly warm atmosphere. If they are pumping into an extremely cold environment you will get insane efficiencies since you are 'going with the flow' with regards to entropy increase.
I'm not sure that actually works out to your advantage, because the heat pumps themselves produce extra heat. But I haven't done the math on that.