Highly unlikely to work
Unless you have chosen the most convoluted way possible to steal Aunt Mary's chocolate cookies recipe, computers tend to be connected to the same grid in bunches. How do you separate the power consumption pattern of a single CPU among a dozen computers in an office? The noise level is just too high, even if you filter everything out (HDs and fans kicking in, LEDs going on and off and all that) but CPUs.
At this point I have a more likely data exfiltration warning: Sleep talking! What happens if some employee talks in his sleep, bad guys are recording him, and he starts blabbering something confidential in his sleep? Danger! Danger!