One of the typical questions that people ask me when talking about the smarthome installation is “What happens in case of power outage?”, trying to target some weak spots of the solution.

Well, usually the simplest answer is that in the event of power loss all happens the same as with any conventional “dumb” home install. But, if we look at some details we might discover that this is not entirely truth. Let’s have a look at some typical scenarios and how can we mitigate the impact.       

With the basic stuff like lights, blinds or ventilation control, you might not be bothered that the controlling system goes down after any electricity failure.  However, as soon as your smarthome integrates things like burglar alarm, smoke or water leak alarm, cctv or keyless access, you might need to have these things working with some kind of power back-up.

In my installation with Loxone I did quite extensive research and gone through various solutions before I got to the one I am happy with. Given the fact that Loxone does not have any custom device to maintain uninterruptible power supply, you’ll need to look elsewhere for suitable solution.

Standard 230V UPS solution

One of the easiest solutions, people usually tend to, is purchasing one of a small free-standing UPS with 230V output. Basically, this is not that bad idea, especially when this power backup is also feeding your home network (router, switch) and potentially other stuff like NAS and IP cameras.

APC Smart UPS 1000
APC Smart UPS 1000

The advantages here are that you do not have to take care about the batteries at all, charging and the whole battery management is integrated in the built-in electronics. If you purchase some of the better models, you might get additional protection between the incoming utility power and sensitive electronic equipment. Also, for some models the status can be read by Loxone and follow-up actions triggered in case of low battery capacity, battery failure and others.

The main drawback here is that conventional UPS systems do have lower efficiencies and a lot of energy is wasted in the dual electricity conversion (230VAC to low Voltage DC and then back to 230V AC). On a top of that, the output of the conventional UPS will be again going to another PSU (or multiple) feeding the Loxone infrastructure, which represents another drop in the efficiency. Now, you might think that we can neglect these energy losses (even if this is 24/7 consumption), but in the event of power outage, when we switch to battery mode, the unnecessary conversion to 230 AC and then back to 24 VDC reduces the potential up-time. Try to run your UPS without any load to see how long does it take to discharge the batteries just with the DC to AC built-in converter on. Then you can add the idle consumption of the Loxone PSU and the whole power wastage is there. Wouldn’t be nice to feed the Loxone infrastructure with the DC battery voltage directly? If you are preferring longer battery time, standalone conventional UPS with 230V output is probably not recommended.



  • Easy setup and integration
  • Surge protection or even ‘electrical firewall’ depending on the device type
  • Can back-up other devices like network hw (switch, router or nas)


  • Disputable complexity level of status reading

  • Energy loss through multiple conversions (mains – battery – mains – 24VDC for Loxone)
  • Single point of failure (smarthome control, home network, NAS, cameras, …) unless you have multiple units

Power supply with UPS function

The other option how to protect the system against power cut-off are PSUs with integrated UPS function. Unlike the Standard 230V UPS, these provide direct DV output from the batteries in case of power loss. This means that there is no conversion back to 230V and thus no associated efficiency loss. This would be the ideal option if …


I came across three types of such UPS power supply units. The common limitation there is the following. All devices I have tested do have just one integrated PSU that feeds both output channels. Typically, you would need an output (say CH1) that has DC 24V for the Loxone infrastructure, and then other one (CH2) to connect to your batteries. To maintain proper charging of the batteries, the output of CH2 needs to be higher than 24V, usually 27.48V (depending on the battery type). But because the two output channels in these units are linked to one integrated PSU, what can be achieved is either that you run all your equipment on 27.48 or more Volts and your batteries will be charged, or you set properly 24V as the DC output for both, and your battery will never charge. There is no way setting the voltage differently per channel, which was my main complaint.

Tested PSUs were:

I have contacted both manufacturers and they just confirmed my observations as “by-design” with responses in the same manner.

“The voltage of CH2 is the same as the CH1, because it is provided by the CH1 with the circuit of the limited charge current. I think it is normal for the UPS system. The voltage will be provided by the battery when the AC power disappears. The voltage range of the battery is about 24~27V. So I think your load must accept the voltage range.”


“… the output to the load can be adjusted from 22 to 28.8 V DC and the output voltage is same for both load and batteries.”


The next question then needs to be: “Is safe to run Loxone on 27.48 Volts (or even a bit more)?”

I did contact Loxone support with this regard and was not surprised that it is not recommend. In their response they mentioned that the tolerance level of supply voltage is +-10%, which would represent range from 21.6 V to 26.4 V=.

What does it mean then, will it survive? I personally know people that are running systems on such higher Voltage because of the limitations described above. It could probably mean slightly quicker wear of some electric parts in the system. I was not looking at the wiring of the units, but I would expect there to be some constant voltage regulator (need prove of this assumption). If so, the higher voltage would be compensated by increased heat in the units itself, and subsequently more heat in the electricity cabinet. Almost all Loxone extensions do have temperature values readable and these can be monitored.

The only bad experience I had was with one type of PIR sensor, that has been tweaked from 12V to 24V using voltage regulator and two capacitors. The fact that there were electronics relays (SSR) resulted that it burned the output channel after raising the Voltage by three Volts and you could smell this all around the house.

PIR sensor that was running for 27.5 Volts ended like this



  • Minimal space requirements in the cabinet
  • Reasonable pricing level
  • Two digital outputs to be integrated (depends on the type of the unit) to read the status


  • PSU integrated with ups function (with all pros and cons)

  • Not possible to set different voltage levels for load and batteries, so you either not charge your batteries properly or need boost the voltage output towards the load which is beyond the tolerance level

Separate DC UPS control unit

After going through the options above, here is my final solution (I am happy with).

It is Weidmüller ConnectPower DC UPS 24V. It is a DIN rail mount unit in robust metal housing that has no integrated PSU. You can buy PSU from Weidmüller to sit on the DIN rail next to it in the same design if you want to, but it works flawlessly with any other 24V DC power supply types. In my case I am using MeanWell HLG series, which is my preferred PSU type.

Weidmuller ConnectPower DC UPS 24V
Weidmuller ConnectPower DC UPS 24V

This DC UPS works the way that you simply connect 24V DC input from your power supply source and in normal operation it passes the Voltage through it with just minimal drop (-0.2V), so you get 23.8V on the output side. The integrated charger makes the appropriate (higher) voltage needed for successful recharge of the batteries (temperature compensated) 27.48 V @ 20°C. In the event of a mains failure (drop of the DC input voltage) the system switches instantly to battery operation. It supports batteries of the total capacity of 1.3 Ah, 3.4 Ah, 7.2 Ah, 12 Ah, 17 Ah, which is selectable with rotary switch.

It also has digital inputs that can be connected to Loxone to give you info about Normal/Battery operation, Charging the batteries and Fault alarm. It provides high degree of energy efficiency, ≥ 96% normal mode when battery is being charged, ≥ 98% normal mode when battery is fully charged and ≥ 98% in buffer mode, when running on batteries.

The price is ranking a bit higher (~200 EUR) compared to the previous PSUs with integrated UPS function, but I think it is worth considering as this device really takes care of your batteries providing the right charging voltage and keeps your output voltage to your infrastructure within the accepted voltage range. This is by far the most convenient solution as I can tell after a year of 24/7 running experience.



  • Proper output voltage to load and batteries
  • Three status output signals to monitor the health (normal/batt. operation, charging, fault)
  • Potential good energy efficiency (depending also on the connected power supply)
  • Industrial design of housing and connectors


  • No integrated power supply, has to be external

  • Higher price

So, if you are looking for solution that will provide you the longest battery run, this ConnectPower DC UPS 24V with some pair of good batteries and reliable PSU might be the best option. I would be more than happy to get your view on this topic so feel free to respond with your suggestions. Ideas like connection solar panels to prolong the battery run might be interesting.


  • Please put a schema with the CP DC UPS 24V with the battery and connection for the signal. Can you have in Loxone by digital input all this status signals?

    • That installation is very simple. You need to have your 24VDC power supply. That power supply is connected to the input terminals + and -. Your batteries are connected to the other two terminals on the TOP of the device (marked Bat + and -). And finally, the output to the infrastructure that should be protected by the UPS is connected to the + and – output. This is enough to make it all work.

      If you want to read some status, you can easily use the bottom terminals (relay outputs) and connect these into the Loxone digital inputs. Simply put +24V on the one side of the relays (terminals 11, 21, 31), and the output from 14, 24, 34 can be then directly put into Loxone digital inputs, providing info about Alarm, Battery operation, and Charging. Obviously, you will need three free digital inputs on your Extension to make it work.

      • Could you please share what type of batteries you are using in the module?
        Also, did you have opportunity to evaluate Phoenix Contact 2868703 Uninterruptible power supply STEP-UPS/24DC/24DC/3 ?
        Many thanks in advance

        • I am using normal two 12V batteries (Shimatsu – Valve regulated lead-acid battery 12V 7.2 Ah), but for the future I will definitely consider bigger capacity. I did not test Phoenix Contact 2868703 Uninterruptible power supply as I am happy user of Weidmüller.

  • Yes, I agree with the approach. I’ve also found another nice solution, which also has a buffered +12V available at the UPS output, this can be very useful in case you may have some +12V stuff to be powered under UPS:

    1- Automatic door lock
    2- PIR burgler alarm sensors, usually powered at +12V
    3- ADSL router

    The unit is the PULS UB10.245 (360 W, 15 A@ 24 V, 5 A@ 12 V, external batteries 12V@ 4 Ah to 40 Ah)

    • Hi Fabrizio.
      I have been considering PULS UB20.241 back then as well. The only down side for me was that this unit uses DC to DC conversion when running on batteries (buffering). That gives stable voltage output while the battery gets discharged on one hand, but the flip side is the energy efficiency that is obviously lower due to energy loss in the conversion. This is completely unnecessary for Loxone and other components I use. These will surely run even if the voltage drops to 20V (which will not happen with Weidmüller’s UPS, as there is a battery damage protection), so there is no need for stabilized and energy inefficient battery output in case of buffering, which is eating up the overall capacity and UPS time.

      • Hi Kops, wish you an happy 2019!

        After a little stop I’m now back again working to my design, thinking to the best 24V UPS solution and re-considering your feedback about the PULS UB20.241 (or 245 if you also would need some parts to be powered at 12Vdc).

        The buck-boost efficiency claimed in the DataSheet is 99% in Power Supply mode, also I see max. losses in buffered mode is 20W at 20A power, while about 7W at 10A power consumption.
        Well, I don’t believe this is killing that much the buffer time to Loxone and its extensions.

        Am I forgetting to consider something else?

        Thanks a lot!

        • Hi Fabrizio,
          It definitely depends on your priorities. The datasheet says that in a battery mode, even if you not take any current out of it, the internal DC2DC circuits will eat 4.2W which I am not saying is a battery killer, just a fact that if your Loxone infrastructure consumes for example 20W, it is extra 21% (and it will be probably more, because this is measured when the converter is in idle).
          So I am not saying PULS is a bad device, you just need to consider if the way it works is the most reasonable for your application.

  • Hi, i am just building my Loxone smart home and have decided after reading your article i want a UPS. I have ordered a Weidmüller ConnectPower DC UPS 24V and associated junk but have some pretty silly questions as I am quite new to DC outside of the basic 12v systems on boats.

    1 – What batteries would you recommend for this. there are many and i am confused.
    2- Does this run on the same PSU as the smart-house?
    3- Any advice on battery storage or location?



    • Hi Simon,
      The Weidmüller’s ConnectPower DC UPS 24V can handle batteries up to capacity of 17 Ah. There is a switch to select 1.3 Ah, 3.4 Ah, 7.2 Ah, 12 Ah and 17 Ah. For 24V you’ll need two similar 12V batteries in series, unless there is 24V battery available. BTW, there is a battery module made by Weidmüller, that can be easily paired with the device directly (and has the temperature sensor built-in as well for better protection). However, I am using normal two 12V batteries (Shimatsu – Valve regulated lead-acid battery 12V 7.2 Ah), but for the future I will definitely consider bigger capacity.

      I have dedicated power supply for the whole Loxone infrastructure only, and that powers it through this DC UPS module.

      Batteries are in a metal cabinet, small rack (originally made for networking components). In the same box I placed the PSU and the DC UPS unit. That was not my initial plan, but it evolved this way.

      • Thanks for the swift response, Its a shame they only support 7.2ah… i was hoping to get more capacity. Like 120Ah leisure battery etc. any idea why the capacity is so small or how i could increase it dramatically.


        • The max is not 7.2, but 17 Ah. But still far away from 120. It would probably not handle the charging current, not sure if there are devices to support huge batteries, maybe there are.

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  • Took me years to find this great post with complete solution.

    Immediately ordered Wiedmuller 5A PSU, UPS and 17AH battery module. Will go all orange, though would be pain to reorganize whole cabinet.

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