[Nut-upsdev] RFC: adding new data "ups.efficiency"

Arjen de Korte nut+devel at de-korte.org
Sat Apr 16 10:05:29 UTC 2011

Citeren Arnaud Quette <aquette.dev op gmail.com>:

> we (Eaton) have created a new data to expose efficiency of the UPS
> (basically it is the ratio of the output current on the input current).
> I know that at least APC should also provide it on some units, since I've
> seen evidence in an EPA presentation [1].
> So I'd like to create the following new data:
> - Name: ups.efficiency
> - Description: Efficiency of the UPS (ratio of the output current on the
> input current) (percent)
> - Example value: 99
> As usual, comments and feedback are very welcome...

Two comments:

1) What would be reported if the UPS is running on battery? There  
clearly would be no input power at that time. What is reported in that  

2) Calculating the efficiency based on the ratio of input and output  
*current* leaves a giant loophole to artificially increase the  
reported efficiency. On an online UPS one could increase the  
'efficiency' by setting the output voltage a few percent above the  
input voltage. Similarly, if a system would have a near unity power  
factor on the input, but a crappy one on the output, you'd also  
inflate the reported efficiency by using the RMS figures.

I'd only see some merit in reporting this, if it would be the ratio of  
input and output real power values. I would be surprised if in a real  
world scenario however if one would get very close to 99% (if not in  
running in bypass mode). A more typical value of a double conversion  
UPS would be something between 90-95% and even then only when the UPS  
is properly scaled for the designed load. The good thing would be that  
people might be made aware how much power they are wasting, given that  
fact that in many cases a UPS will not be operated near the optimum  
efficieny load.

Best regards, Arjen
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