Originally Posted by Gregor
The other thing to be aware of is the inclusion of active power factor correction. This reduces the load on the AC supply for the same output. Iotas and some Meanwells do not have this. This feature adds about $100 to the cost. That feature is included in all server supplies.
This power factor issue can get a little technical on what's involved. For example the power factor is a non-issue when you turn on an standard old lightbulb with the tungsten filament. (The power factor is "1.0")
If you've got a lot of AC motors on your home, these motors have a lagging power factor that results in somewhat higher amperes flowing through your AC power breaker box to your motor. Higher amperes at least as compared to if the AC motor could have a "1" power factor.
But, and this is a big but, you only pay for the actual watts going through your homes electric utility meter, regardless of what the power factor is. The average home has a lot of AC motors such as the airconditioning systems that cause a LOT more power factor issues than a single computer power supply might have.
So, that power factor is more of an issue with the electric power company for their big power transformers than it is for the average home user. And, in fact if you drive along a country road following a three phase power line, you might find giant capacitor banks connected across the three phases every so often. Those capacitor banks are used to correct the power factor back to the ideal "1.0" for that powerline feeder.
(Power factor involves the voltage and current going through a powerline being exactly in phase. There are people out there that sell quack units (yup, capacitor banks) that supposedly reduce the current going into an home electric motor. All these things are doing is correcting power factor which does reduce the motor current. But, those gadgets have absolutely nothing to do with reducing the actual cost in kilowatt hours going into those electric motors.)