Energy consumption monitoring - monophase 4 lines

Good morning to everybody,
my name is Antonio and I’m a 52 years old electrical engineer.
I recently moved from OpenHAB to Home Assistant and I’m now trying to improve/increase my home automation.
My HA set-up is the following:

  • 1x Raspberry Pi 3B+ (connected by LAN)
  • 1x Aeotec USB Z-stick Gen5 (connected by USB)
  • 1x Broadlink RM4 Pro (Connected by Wi-Fi)
  • 1x In Wall Dual Relay Switch Module

Installed Integrations:

  • Z-Wave JS (1x In-Wall switch)
  • Broadlink (2x RF motorized curtains + 1x IR Hi-Fi)
  • Daikin AC (3x Air Conditioners)
  • Reolink IP-Camera (1x Camera)
  • Internet Printing Protocol (1x Epson Printer)
  • LED BLE (1x RGB Led strip)
  • LG WebOS (1x LG LCD TV)
  • Magic Home (2x White dimmerable LED strips)
  • LGE Devices (1x LG Washing Machine)

Things are working quite good, and as already told you, I’d like to expand my system; next steps will be:
1: adding new z-wave In-wall devices for light switches (most probably 3-4 more double switches)
2: Alexa integration (on going by HACS)
3: Energy consumption monitoring

My electric switchboard is made by (230 V a.c. monophase distribution):

  • 1x Magneto-thermic-leakage detector (main switch breaker, non-SMART but motorized for self-reclosure)
  • 4x Magneto-thermic switch breakers
    • 1x16A (Home appliances)
    • 1x16A (Electric Plugs)
    • 1x16A (HVAC)
    • 1x10A (Lights)

The intention is to monitor the following consumptions (I prefer by clamps):

  • Total consumption (Line-IN) by clamp
  • Home Appliances by clamp
  • Electric Plugs by clamp
  • HVAC by clamp
  • Lights (calculated by difference)

Therefore I’m looking for a 4 channels/clamps energy monitoring but I’m not able to identify the best suitable device: any advice?
I would like to avoid Zig-bee and Tuya, so the choice was mostly between z-wave or Wi-Fi…
I found the Shelly 3 EM available with 4 clamps but I’m wondering if it suits my needing: Is it capable to measure the consumption from 4 feeders in a monophase network?
Should you have any other suggestion it will be much appreciated.

Thanks in advance for your help!

Best regards,

The Shelly EM will only monitor 1 line.
The Shelly EM2 will only monitor 2 lines.
The Shelly EM3 will only monitor 3 lines.
Since this is 4 line feeder why not go with the Shelly EM (4 of them) and get the correct sized coils for the main consumption.

I have the Shelly EM2 for monitoring the whole house draw to compare with the smart electric meter (no optionto pull monitoring off from it) from the power company.

Thank you lordwizzard for your kind reply.
It’s also a matter of money: 4 of them will cost more than 200€ (and 4 IP addresses) while a 3EM with 4 clamps will cost less than 150€ (1 IP).
A compromise would have been using 2 of EM2 for about 150€ , but I understood that there is only 1 output for each device (sum of both channels) making impossible to verify the correct power-feeder among the 2 connected.
Are you using the EM2 with modified firmware or not? And which integration?

Thanks and regards

No modified firmware and using the standard energy dashboard with the Shelly integration. So I do not do anything like summing by itself, I let the energy dashboard do that. I don’t see how you can use 4 clamp coils on a EM3, it just won’t work. It can only do 3.

For around a tenth of that cost (twenty something euros) I build a clamp power meter years ago which is not only accurate but also rock solid since the very beginning :rocket:

All that’s needed is a esp (or rp2040) of choice and 4x a pzem004t v3 :clamp:

I was maybe miss-driven by this picture on the Shelly web site:

It’s written than this scheme only works with 3-phase & 4 wires distribution systems; but I’m still wandering if it suits my scope… Let me explain it better:
Clamps on Phase A,B & C could be used to measure the power flowing through 3 (of the 4) distribution breakers (and this should work out of the box); the 4th clamp on the neutral (Phase N) connected to the feeder (Neutral or Phase, using the correct verse) should allow to measure the total current; but I’m not sure if this last input (supposed to measure only current leakages) is exposed at the same way of the others…

Can you please confirm my understanding about the unavailability of separated measures of power for each channel? Maybe I’m wrong and using 2 x 2EM can be the solution…

Thank you Orange-assistant, but what about the data transmission between ESP module & raspberry? They’re far away each other so I should need wi-fi transmission which makes things more complicated…

As you’ll want to pull frequent current readings off the energy monitoring device I’d recommend WiFi as the transport protocol instead of z-wave. Z-wave can get overwhelmed with frequent data transmissions and it also kills the battery of any devices which are in listening mode and are within the return path to the controller for the energy readings.

So you really don’t have a 4th phase, it is actually the neutral that can be monitored for theft/leakage. Probable the leakage is the more important factor here. Just understand the the neutral will have to carry the total sum of the 3 phases so it would have to be the biggest coil.
You’re spending on something that is not normally needed. Do the normal 3 phase monitoring. You can always add the last coil later if needed.

Hi lordwizzard, for sake of clarity I’m here attacing the electric scheme.

I think this can be a good compromise for the moment: Channel A for Appliances, B for plugs and C will be the sum of HVAC & Lights.
In this way I should be able to read the total consumption without make any changes (I understood that Shelly 3EM already provides an output as a sum of the 3 monitored channels).

Should you have any other suggestion (including different devices) it will be much appreciated.


ESP’s come with wifi included - even the $2 d1 mini (clones) have in-build antennas. :signal_strength:

Btw. a shelly EMx,y,z is has also “noting more” than a esp inside :bulb:

I went a little deeper in your suggestion and now it looks a little bit more feasible to me… But this will require once again 4 new wireless connection (and IP addresses) to be managed by the modem/router and this is something I was trying to avoid (while using shelly 3em will require only one).
Also still wondering if this scheme could work for the scope:

Maybe not out of the box and nor using Shelly Smartphone app, but under HA it may fit the scope.
I’m thinking about to start by procuring the 3 clamps and testing how it works in 4 clamps config (by temporary moving channel C under the neutral terminals and see if (and what) reading on HA is available.

Here below switchboard picture: I’m ging to replace the 3 2modules-switches by the relevant 1-modul model, adding one more feeder.

P.S. what you see on top of the breaker is the door bell not connected at the moment.


While this is theoretical possible (but in no way “required”) why would you want waste 3 extra esp’s if one esp can handle 4 pzem004t’s units with ease? :thinking:

You could also go wired btw :wink:

This is new for me… unfortunately (bit it’s my fault) I was not aware about the 4 channels available… And I’ve already ordered Shelly 3em…

I’ll start with Shelly and meanwhile I’ll procure all the all the staff to experiment… in case of success I can resell the Shelly quite easily…

Yesterday I replaced all old breakers with new ones (1 DIN module) to save some space for the Shelly, installed a earth bar to connect all grounds (bit it’s still a mess :joy:) but still need to work on it…
Pictures is self explaining

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Shelly 3em up and working. Also HA integration (based on mqtt Mosquito) looks to working… I’m monitoring the power factor because it looks too low (close to 0.1) when the current is very low…
And it looks that the 4th channel (supposed to be clamped on the neutral wire) doesn’t provide any output in HA; maybe in the Shelly app (and web page) it just provides a digital output as an alert and nothing more; hence, shelly em3 cannot monitor 4 different circuits…
P.S. Shelly em3 is a little bit more than 1 DIN module, but because of it’s reduced length can be fitted in the panel, leaving few millimeters hidden under the panel cover (but the signalization Led is still visible).

I’ll keep you updated on any new discover.