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Killy_Vorkosigan said:
Cyran said:

How would my power company know how much power my PC using vs what being pulled out of the wall?  The only thing my power company can measure is the power being pulled from wall.  How could they possible know that my PSU loosing x wattage between going into it and coming out the other end? 

Waveform. Actually it's pretty easy just by looking at the harmonics created by your PSU to discriminate your computer wattage, with a reasonable margin. Just by analysing several weeks of your power consumption times this is something doable even if the metering is performed at the counter. Imagine electrical companies, with the 'smart' meter that have been installed in the last 5 years, have access to millions of load profile and can statistically make such claims.

That may be true but that is not something they looking at when they calculating your power bill.  After researching what is meant by Apparent vs real power is that

Real power =  Apparent power - Reactive power  

Obviously measuring reactive power that getting return to grid is easy to measure and that is what going on.  PSU efficiency on the other hand is power lost to heat which would still be consider real power from power company and you are being charged for.