In practice so far new CPUs were much more power efficient than older ones - so much that this approach makes little sense but .... it is worth noting that one

In practice so far new CPUs were much more power efficient than older ones - so much that this approach makes little sense but .... it is worth noting that one of the reasons this might remotely work is on slide 7: Diminishing growth CPU performance / end of Moore's Law. I'm fairly optimistic about the 10nm node still providing a power saving boost but in the long run this sort of thinking could interesting.