Posted on 2009-12-16
Last Modified: 2013-12-11
In my office we run 17 APC 450 PRO Uninterrupted power supplies, based on the power consumption math.
USAGE: 450-watt APC on 24 hrs for 365 days
Total usage = 24 hrs per day x 365 days = 8760 hrs.
8760 hrs x 450 watts = 3942000 watt hrs.
3942000 watt hrs / 1000 watt = 3942 kilowatt hrs
3942Kwh x $0.18 = 710.10 per APC unit per year.
17 units removed  17x710.10=$12,071.70
 Is this a correct calculation for yearly energy cost for these 17 UPS, or do they use less power during normal usage?
My base wattage came off the data plate on the back of the device.  
Question by:slamboy
    LVL 23

    Accepted Solution

    The watt hours would not be significantly more than the power consumed by the devices it is powering.

    You can get a better idea of the watt hours with a Kill A Watt Electricity Load Meter and Monitor

    Run the station for 24 hours with the UPS then again without it. You will know exactly how much it actually uses.
    LVL 2

    Assisted Solution


    As I recall and practice, the usage of a UPS is to supply power in the absence of AC Mains. The only time that a UPS draws power is on the return of the AC Mains after a loss of same. UPS do not pull power except to float the batteries in the units. So what is your question?

    Oh, in point of fact the rating of the UPS is the VA power output that can be supplied during a AC Mains loss. Your APC 450 Pro's will supply 450 va per second for the rated run-time of  equipment load. This differs between machines unless your office uses the exact same unit in all 17 locations. Same monitor, CPU, printer, speakers and accessories.

    Now if you are trying to measure the power usage of your office then the offering of edbedb with the Kill A Watt is an excellent choice.

    I hope that this helps clear things up.

    Author Closing Comment

    Yes, we'll just have to measure it ourselves, thanks for the link!

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