Ok, i've seen a lot of people referencing Iwata. Here is what he said.
Note, in this instance he was touting how efficient the system was, so he was giving the lowest ballpark figure.
If the Wii U is rated at 75W, I don't see why the PSU wouldn't be 110w. I know, I know, the demo units produced about a year and a half or more ago had 75w PSU's. ei, not indicative of the final design.
I guess what I'm getting at is that we don't know anything other than Iwata saying that the WiiU can consume 75W under full load. He never mentioned the PSU, anyone who says otherwise are fabricating a story to further their agenda. Why someone would feel the necessity to have said agenda is beyond me.
Hell, the Wii U could be able to disable unused cores. That would explain how a multicore system is 99.9% BC. Could also explain how "depending on the game" "40w could be realistic."
My two cents, but they seem lucid to me...