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Cyran on 26 September 2023
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haxxiy said:
Cyran said:

I think you have a misunderstanding of what PSU power efficiency mean.  If your computer require 500 watts.  Your PSU is 80% efficient at 500 watts then that mean the PSU going to require you to draw 625 watts of power from the wall to provide your computer 500 watts of power.  If it 90% efficient it would only need to draw 555 watts from wall.  Therefore your real power draw from wall would be 70 watts less therefore reducing your power bill slightly.   

That's exactly what I meant.

Most people *think* they would incur the cost of that extra wattage, but that's just apparent power, which residences don't pay for in most places.

So unless you're running your PC on the site of some industrial enterprise (which would have to pay for that apparent power), it shouldn't reduce your power bill.

There a disconnect somewhere between us.  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? 

EDIT:  I think I figured out where the confusion coming from.  You associating Reactive power with PSU efficiency which is wrong,  PSU efficiency is showing power lost as heat which would count as real power usage  You not charged for power drawn that is return aka Reactive power.  You are right that we are not charged for power that is reactive but that not what PSU efficiency is measuring.

Last edited by Cyran - on 26 September 2023