Technically, a good heat pump has an "efficiency" of 250% ~ 400%, depending on conditions and such. But a good one will work for both heating and cooling, so that's a wash.
actually you are wrong, heat pumps (air conditioners) typically have a coefficient of performance that is greater than 1. this means that they move more heat energy from the cold side to the hot side than they consume in moving the energy. this is possible because they are just moving the heat energy around, they aren't creating or destroying it.
But it is easier to cool by 4 degrees than heating 40.