While PC users might be familiar with their machines under-clocking themselves to save energy, reduce heat, and prevent damage, the idea is new for Microsoft’s Xbox console. According to an interview Gizmodo had with Xbox’s General Manager of Console Development, Leo Del Castillo, the new Xbox One will be able to cool itself down in a multitude of ways, including "dialing it back to a lower power state."
The Xbox One is aware of the current temperature it is running at and is able to take action to cool itself down. The unit will first start by pushing up the fan all the way to its maximum speed – although Microsoft does not anticipate the need for the unit to do so under normal environmental conditions.
If after increasing fan speed, the unit still does not cool down, the unit will be able to switch itself to a lower power state in order to protect itself.
We are currently unsure of how the under-clocking works and how it might affect game performance. Although as stated above, this is a last resort for Xbox One and should not occur under normal environmental conditions.