PC Peripherals UPS efficiency

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ch@ts

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We've all been talking about psu efficiency, but no one's thought about ups efficiency. I tried looking up some numbers on the net, and I found hardly any literature.
One graph I found by APC showed that most UPS's had about 50% efficiency at low loads.
What is the efficiency when the UPS is not on battery back-up?

And does it make sense to buy a high capacity UPS for a rig that doesn't consume too much power?

My rigs power consumption is about 250 watts, including the monitor, which at about 70% psu efficiency draws about 360 watts from the wall.
I've got a powersafe 1KW UPS. Now 360 watts is less that 50% load, does this mean I'm drawing about 720 watts from the wall, about 3 times what my PC is actually consuming?

How do the batteries effect the efficiency? Are newer batteries more efficient?
Which UPS is the most power efficient?
How do I measure power draw at the wall, cheaply?
 
The efficiency figures mentioned are only during the times the UPS is on backup mode. When it isn't on backup, the UPS does not affect efficiency one bit.

Yes ideally you should be matching the power handling capacity for maximum efficiency. The reason most people buy higher VA rated UPSs , is because they tend to have a larger capacity battery and hence a longer backup time even though VA and battery capacity aren't really related.

Unfortunately the most efficient UPSs are also the most expensive - the online UPSs. IIRC efficiency is as much as 90%. BUT, they work all the time, and hence their efficiency comes into play the entire time the PC is on.

If i'm not mistaken, Batteries do not affect the efficiency.
 
Are you sure about the efficiency when not on battery? Cos, the ups charges when it's powered.
But if the efficiency figures do not apply to the times when the power supply is normal, it's a big relief.
Thanks for setting my mind at ease!
 
I assume the charging cycle while power is available is also calculated into the efficiency figures for the time the UPS is on battery mode.

The point is, the efficiency of this charging cycle is separate from the efficiency of your PC while it is on regular power.
 
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