I actually wonder if Nintendo hasn't done something to hold the power usage down at this point in time. As I understand it, Nintendo themselves said the system would use 45 W at peak.
So why are they all using about 33 W? Did Nintendo just do extra efficiency modifications in the last few months? Or are the launch titles specifically not using all of the available power? Or is it just that they haven't tested the appropriate games?
I don't know.
Let's assume a case where the game/console runs at 35W. With a power brick with an efficiency of 70% that means that it draws 50W from the wall, add another 20% left for safety (because efficiency goes down with time, etc.) and you end with 60W. With the power brick being 70W, where are the other 10W?
Who knows, maybe they'll do what happened with the PSP or the 3DS and launch a firmware that increases the speeds of the CPU or the GPU (or maybe both).
I'm fairly certain that Nintendo wouldn't have been describing power draw from the wall, specifically because of that efficiency issue - if they were to say "the system draws 60 W from the wall", then after a year, it would draw more, and their claim would no longer be accurate. But the power draw from the system is easily measured.
The other issue is that Nintendo said it could require up to 75 W, but would typically use only 45 W. Based on 70% efficiency, 45 W becomes only 31.5 W, which is below the number we've seen for most games. It's more likely that the 45 W number is the system power draw, not the total power draw at the wall, in my opinion. But then, I'm no expert.