Jeeniouss!

So, heat pumps are more than 100% efficient, in that they move more heat than the energy needed to run them. Therefore, the neighbour should also install this system, creating a closed system that keeps both houses warm at better than 100% efficiency. I think this might solve all our energy needs, and global warming in one go. Tsk, to think the so called scientists have been trying to get fusion working when this solution is already practical.