Inside sources claim that Nintendo has tweaked the Wii U to run the Unreal Engine 4. We've heard multiple times that the Wii U was still in a tweaking process with Nintendo, with new specs cropping up with every dev kit
Nintendo tweaked the Wii U to make sure it can run UE4.
I've just heard it from a friend that Epic has UE3 & UE4 up and running on Wii U hardware.
His source works for a developer, one that I shall not name, but they do work on pretty much every system. So that alleviates any concerns that I didn't have over the Wii U power issue as far as I'm concerned.