Wii U is currently the 'greenest' console on the market
There were months of speculation whether the Wii U would outclass its current gen competitors in terms of graphical capabilities, or whether it would just be a poor man's next gen console. Turns out, the Wii U is actually on par with the other systems. Sure there might be some compromises when it comes to graphical fidelity, but in general, it keeps up well with its current gen brethren.
However, the one area where the Wii U is far superior to both other consoles is in performance per watt. It provides an equivalent graphical and gameplay experience to other consoles, while using less than half the power. Wow!
I'm not one for technical mumbo jumbo, but essentially the way Nintendo made this work is due to the CPU and GPU being bonded together into a single assembly, which would concentrate the heat.
When actually looking at the numbers, the Wii U stays the same amount of wattage, sometimes even lower, when running various applications. When put head to head to head with Fifa 13, the Wii U managed to stay at 32w, while the Xbox jumped to 76.5w and the PS3 Super Slim jumped to 70w.
If, like me, you're confused about all these numbers and technical jargon, just know that the Wii U essentially consumes less power to run itself and various games and apps, than its console counterparts do. That means you can rest easy knowing you'll probably never run into an overheating issue.