Here's the difference: banks have every incentive to try to reduce their power consumption, Bitcoin miners have every incentive to increase their power consumption.
Well that's one way of writing /joule, I suppose.
(kicking CPUs and GPUs out of the contest probably did a lot to lower power consumption, but I wonder if the growth of the network has overshadowed that)
My original point was that when a technology comes along that allows banks to be more energy efficient, the incentives are all in place for banks to adopt that technology and reduce their energy consumption. There is never an incentive for a Bitcoin miner to reduce their power consumption.