More than 100-percent efficient.
http://books.google.com/books?id=vc8DAAAAMBAJ&printsec=frontcover

"It doesn't give you something for nothing..."   Eh?

"But it does operate at more than 100% efficient..." Aha...

It is true if we consider that external heat from the environment is "nothing", i.e free. Then a heat pump has an apparent efficiency >100% (a not real efficiency that in this case should be called "COP"): the quantity of heat energy transfered from the environment to the system or from the system to the environment is more than the energy needed to power the device.
The underlying principle is that we don't theoretically need energy to transfer a certain amount of heat from one point to another (but our machines have not 100% efficiency). It is a well known fact from conventional physics. Physics laws prevent OU in a closed system, but not in an open system.

If we could loop the device, it would lead to an apparent perpetual motion which in fact is a system exchanging energy with its environment. It is theoretically possible but not yet feasible because the real efficiency of the heat pumps is not enough. Some have calculated that the future magnetic heat pumps could have enough efficiency for that. In any case such systems would still increase entropy according to the physics laws, but from a practical viewpoint and while the environment can provide/absorb heat energy, it would be "free" energy.