Energy consumption vs % utilization?

Speaking on Deep Background, the Press Secretary whispered:

[KWH meter]

Instead of doing all this, just buy a Kill-A-Watt meter for about $30, and
get an instant reading of Watts, Amps, VAs, power factor, and KWH.


I've not seen anything near that cheap. The spec sheet is
rather lacking but if it does the job..

Note that it's 120V only and 15A; lots of racks exceed that.