Hager Energy Meter ECA381D

I received an offer from my electrician to build in a ECA381D in my appartement. This energy monitor has two rj45 modbus (agardio) interfaces. The same energy monitor is also available with M-Bus or Modbus (both with screw-fastening technology) or as said as Modbus (Modbus agardio) available. Which one would you prefer to use with openhab? I don’t know which interfaces is the most hassle free to bind it to openhab.

Before spending 800 Euro for the installation I really would like to be sure that the integration into openhab will be as easy as possible for me as a beginner.

Any advice and suggestions will be greatly appreciated.

Thank you very much.


openHAB has a ModBus Binding which allows you to connect both Modbus RTU and Modbus TCP slaves.
So first i would prefer Modbus over M-Bus in this case.

  • For Modbus RTU you would need to have a serial interface to connect the Energy Meter.
  • For Modbus TCP you would need to get Ethernet to your cabinet.

From a beginners view i would prefer the Modbus TCP meter,
because you don’t have to worry about getting the physical bus running that much.
You would connect the meter to your ethernet and only need to set the ip adress.


I have checked the hager page, because i was not sure about the term agardio.
So i have to adapt my statement:
Before prefering this one, i would check if this is a native modbus tcp meter,
or if they made proprietary changes to make it useable exclsively for their agardio portfolio.
If it only can be used with their energy monitoring i would switch to modbus rtu.
If it is plain Modbus TCP with just a marketing name i would prefer that.

Hello Jerome
Thank you very much for your answer again! I really appreciate that. I fear that the Modbus agardio is a proprietary Modbus from Hager but I have to check with Hager first. It’s sometime hard to get a technician on the phone who really knows all the technical details. If in doubt they just say that it’s a native modbus tcp meter…

Regards Manuel

Hey Manuel,

I have read a bit further.
It seems that the agardio system is just a Modbus RTU (serial) System which has some cables you can buy and connect to an “agardio master”.
So if my readings are correct, the native Modbus Energy Meter would be the better choice.
You would then have to connect a serial adapter (eg a PI shield) to you openHAb instance and connect the meter with a shielded cable. :slight_smile:

Hello Jerome
Very kind of you. Thank you so much. Uff, this is really on the edge of my capabilities with all this different protocols and standards bringing to my openhab PI. Sometimes all these challenges make me really headache and sleepless :smiley: I have to figure out first all our input. There are also USB to RS-485 dongle on the market. Questions over questions.

I’m a little bit afraid of spending 800 Euro for the whole installation and then sitting there an not being able to benefit of the new hager meter.

Regards Manuel

Can’t tell you much about the price, but since Modbus is a standard it should be possible to get it connected to openHAB. :slight_smile:

Hager has an excel spreadsheet with all available Modbus registers for their energy meters on their homepage, so it should be possible to get everything needed (or even send commands to the meter if needed). See: https://www.hager.de/modulargeraete/zaehler-und-messgeraete/energiezaehler/ecr380d/992039.htm#Downloads
(This is for the ecr 380, but i think the only difference to 381 is that 381 is produced for the swiss market. They should be similar for the Modbus interface.)

Hello Jerome
Very kind of you with all your information and help. I really appreciate it. There would be another approach to I was thinking about to get the electric usage direct from the main power meter in the basement. This would be a much cheaper solution. But there are also still a couple of open questions.

Greetings Manuel