Where the Watts Go
The cooling load of a data center is, to a close approximation, its computing load plus the losses in the power equipment that feeds it. That is the whole starting point, and it is routinely forgotten. People discuss cooling as a matter of efficiency, as if it were a percentage to be trimmed, when it is first a matter of volume: every megawatt contracted for computing is a megawatt of heat to be rejected, in every season. Faraday's read: read power usage effectiveness as a question about design freedom and climate, not as a grade. The industry average has barely moved in years, while the best fleets sit far lower. The difference is mostly in who controls the building and the hardware inside it.
Knowledge check
Why can raising the temperature in a data hall improve its reported power usage effectiveness even if total energy use barely changes?
Show the answer
Power usage effectiveness divides total facility energy by the energy delivered to the information technology equipment. Server fans are counted in that denominator, so when warmer air makes them spin faster, the denominator grows and the ratio looks better. Some overhead has simply moved from the building into the server.