POE as UPS system concept

Hi All
i wanted to discus what are your thoutgs,
of POE as entire home UPS system for computers, sensors, hardware you dont want to go off ever

i am implanting CAT6A on my entire home…
and i have a poe switch …(that will run on UPS power)
there are allot of POE devices already i will not get into that…
but i came across POE spliters , and it got me thinking

there are allot of single board computers that can use the spliter
DIY smart locks are also able to utlize the spliter (big adventge when the power is off)

also thinking about power consumption moving all my media systems/pfsense box to a 12V single board computers
will reduace my overall power consumption in the home…
but the initial buy will be very expnsive spliters + computer
right now i have somthing like 4 desktop PCs(old ones) running at all times…

anyone did somthing like that? maybe can give me some pointers ?


I’m doing it more/less as you described:


  • PoE switch powered by a APC UPS
  • central devices (NAS/media server/openHAB/…) next to the UPS powered by the UPS directly

Upper floor devices powered via PoE

  • remote devices with Android for UI
  • remote RaspberryPi for radio dongles (Zigbee/ZWave/RFXcom) with Raspi-PoE-HAT
  • WiFi access points of course
  • “non-PoE” internet router/DECT base station (“Fritzbox”) powered via a 802.3at PoE-splitter

But:I wouldn’t expect power savings from that because of the power loss over the long thin network wires…


yep i did not think about all the USB devices i need…RM2, SonffRFBridge , CC2531
dont want them ever to go offline

any idea of USB hub that can be powerd by POE/12V using spliter ?
somthing like this but that will not burn a hole in my pocket … i need 4

this has 12 volt in for aux power

I’m using this thing (802.3at):

and this (802.3af):

Both can be adjusted to 5V/9V/12V, so may source the voltage for your USB hub.

If the power they are able to deliver is sufficient for your 60W (???) USB hub depend on the power need of your connected USB devices…

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You are cascading power supplies amplifying power supply losses. PoE was designed mainly for the convenience of not needing to run extra power lines for Ethernet devices. In my experience it is not generally power efficient.


Exactly. In addition to the power loss through thin network cabling as said above.

BUT: If one tries to get all relevant system components powered by UPS (which are potentially spreaded over the whole home/building), then it might be more power efficient having a single big UPS powering it than having many tiny UPS’s despite the added losses imposed by the chained DC/DC couplers.

Probably not that easy to judge :wink:
For me, the convenience predominates…

If somebody is interested in the figures at my side, here is my power consumption via the central UPS:

  • Whitebox ESXi (i5, 32GB, two spinning discs, four SSD’s, 10Gbps LAN)
  • managed Switch PoE 802.3at, 24x1Gbps + 4x10Gbps)
  • two SBC’s in the basement
  • one RaspberryPi remote with PoE for the radio dongles
  • three dual-band 802.11ac access points on PoE
  • three Android-based IP desk phones on PoE
  • DSL router/DECT base (Fritzbox) on PoE via splitter

Total average consumption: 115 Watts

EDIT: Just checked the power sourced by the switch for the above PoE devices …
average 37 Watts, peak 50 Watts, see:


While this is technically true, in reality it’s probably relatively low so long as you’re using “real” PoE, and not some sort of mid-span injector that injects 12v!

By “real” PoE, I mean 802.3af. This uses relatively high voltage (~48v), which in turn means low current and low loss. Loss (or dissipation) is the square of current making the dissipation considerably less at 48v versus 12v (1/4 of the current, so 1/16th of the loss). This keeps losses on the cabling reasonably low, and makes it a reasonably efficient way to distribute power in most residential settings at least. Maybe a mains system might be more efficient, but possibly not as a PoE system running at a higher load is likely to have a higher efficiency switching converter than many cheap mains bricks.

The alternative is to use a load of 5v or 12v adaptors (or whatever voltage different units like) for every unit. These will also introduce considerable loss…

I have a similar system to @curlyel - a UPS in the server cabinet, and various WiFi and computing systems running off a PoE switch. It’s a load simpler and more manageable than mains supplies everywhere, and has an added advantage that I can power cycle equipment remotely through the ethernet switch.

Just avoid the cheap 12v injectors that you’ll find on eBay etc…


i have 802.3af… but i am planing to buy cheap spliters
is that ok ?

thats just great one Q dou

what the hell are you doing with 3 desk phones :slight_smile:?

These are Android tablets with PoE … and yes - with a telephone handset. One per floor :wink:


The type I would avoid are the passive ones. These are basically just a DC block (ie a few capacitors) that allow you to inject a DC voltage onto the ethernet cable, and then you use another one at the other end to take split the power off to power the device -:


These aren’t 802.3af devices - the issue with them is you’ll power them with a power brick (5v or 12v normally) and they therefore have the issues I mentioned above with high loss.

Cheap 802.3af injectors are probably fine - although I would probably recommend a central PoE switch - something like the Netgear (which is what I have) although there are many others I’m sure.

Splitters such as @curlyel posted above are fine I’m sure - although I’m not sure if they are cheap or not, but that sort of thing is the way to go.


To future proof you could look at the newer 802.3at switches.802.3at can provide more power per device than the older 802.3af standard.

Nice can it also act as dashboard? let say habpanel

i have this switch


not planing to use any passive ports… not sure if i even have them

i am talking about only spliters , i was not planing to jump wire all cables with many injectors and not even with a cheap one from china

In general, yes. I have a Grandstream GXV3275 on my office desk. It is running Android 4.2 and you can install Apps on it.

That’s the main intention for having these. If you consider buying some, pay attention getting some newer ones because of the Android version. Grandstream is providing software updates (features, fixes) but never brought Android OS upgrades (at least not for my devices).

Won’t buy anything older than GXV3370 of GXV3380…

… as example won’t run a recent version of the openHAB Android app anymore… :frowning:

As I said, there are not that many alternatives with PoE out there…

I use a power bank plugged into charger to power my Rpi


Indeed, not able to run the Android App, but not needed for habPanel or the new openHAB3 UI

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i am still trying to disgust the :phone: part

dont get me worng i use skype at work, but i have a pretty decent headset , and this all thing just seems redundant

other then the fact that it looks freaking awesome :slight_smile:
it remainds what imagined as a kid ,the home of 2020

Let me explain my usage.
I am running doorPi as a SIP video doorstation, connected both to my Fritz!Box. The Grandstream can be configured to show the mjpeg video stream besides the SIP call, giving me a nice terminal for my doorstation.
As a sideeffect, I also have a control panel for openHAB on my desk, so no need for a wall panel like in other rooms.
And, of course, you can run a Skype client on it, it has a build in camera snd support for headsets.

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