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UPS input load (feddit.org)
submitted 1 month ago by dieTasse@feddit.org to c/selfhosted@lemmy.world
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Hi all, What is UPS input load and how can that affect the power draw of devices plugged into it?

Context: I have an Eaton UPS. Into it I plugged TP Link smart plug to measure how much my homelab draws (1 truenas server, 1 rpi and a switch). These draw about ~29 W when under low to medium load. Almost every day (different time) for couple of hours, however, the plug measure about 6-7 Watts more (~36 W). I have checked both linux devices and they were doing basically nothing. Then I looked into TrueNAS monitoring and noticed that the start and end of each event is exactly the same time when UPS input load is increased from 0 % to ~6 %.

What is this UPS input load and how is it possible it affects measurements by a device that is plugged into it (the UPS) - NOT the other way around? Thank you

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[-] SuperiorOne@lemmy.ml 2 points 1 month ago

UPS devices normally uses wall (input) power, and switches to battery when input voltage is out of the target thresholds. So, input.load should represent the percentage of current wall power (in VA) relative to UPS's max rated input power (VA). If your devices uses more power, input power from wall should increase as well.

If it's peaking in certain times, it could be due some scheduled job temporarily increase CPU frequency, or automated tasks like file system snapshot might power-up/spin drives longer than regular usage.

[-] Strit@lemmy.linuxuserspace.show 2 points 1 month ago

So what is the TrueNAS server doing at this time? Have you checked the logs?

I would image it might be some backup, snapshotting or optimization.

[-] dieTasse@feddit.org 1 points 1 month ago* (last edited 1 month ago)

Truly nothing. I haven't set snapshots yet, I have TrueCloud backup but thats at midnignt. I have checked htop and there is virtually zero activity (same as when the power draw is 29 W). I have only two apps on truenas and they also didn't do any indexing or anything). As mentioned above the only difference that I spotted so far is the ups input load and the times of event start/end match perfectly in all cases (but then again UPS is powering the tp plug and on, not the other way around).

this post was submitted on 16 May 2025
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