I would still go 
in 2022 
Very accurate and still (very) cheap 
Yes, seems to be O.K. But taking a lot of space…
One can install it quite compact if wanted/needed.
Picture source: Measurement Electrical consumption with Ubidots Industrial & ESP32 + PZEM-004T – PDAControl
It’s not a lot of hardware and the pzem004t modules should be even stackable with proper screws, spacers, nuts, etc. 
Much easier and probably safer setup. I’ve got the single phase version and it works great. Firmware can be modified easily if you want to bypass the Emporia cloud and app and tie it directly to HA.
As the board uses a Beken 7231N (CBU) and the BL0942 chip for energy metering this firmware should work: GitHub - openshwprojects/OpenBK7231T_App: Open source firmware (Tasmota/Esphome replacement) for BK7231T, BK7231N, BL2028N, T34, XR809, W800/W801, W600/W601 and BL602
I have used it on several light bulb, they work flawlessly with the firmware.
I think I’ll try with ‘Peacefair PZEM-004T V3 Energy Monitor’ with ESPHome…
Looks like this is cheapest solution… For 3 sets = 22,8EUR with delivery…
In the end it was quite easy to set up the PZEMs, the first “difficulty” was to descide which ESP-board to use, and from there how to wire it, the second is that the PZEMs have an internal addressing that needs to be updated for two of them if they are to be connected to one sinlge ESP-board, how to is described over on the esphome.io webpage
I settled for a DIN-rail setup:
ArduiBox ESP - ESP32 Prototyping DIN Rail Case (inc. ESP32 Board)
There are cheaper solutions, but this one was convinient for me.
My setup has been working flawlessly for nibe nonths now, monitoring the boiler (geothermal heat pump).
is there any more information on this topic?
I recently installed one of them. Disassembling and flashing with OpenBK is quite easy, however the BL0942 onboard is connected via SPI but OpenBK currently only supports BL0492 over UART. Therefore I had to modify the circuit with some extra wires, it now works, but if you have no experience with such mods its probably easier to just go with the Tuya Integration.
Could you please give some feedback on iammeter.
Is it able to deal with those noisy (modern) loads - how far off is it from what the main utility meter is showing?
Well, at the beginning i entered all data: price per kWh (low/high) and fixed costs and when i checked my electricity bills for a few months end prices were pretty close, so it seems that it’s measurement is pretty accurate. Honestly, i didn’t check kWh numbers (silly me…), but i guess i just forgot to check since end price is pretty much the same, and in that case kWh numbers are, too.
So far iammeter works like a charm, no dropouts, glitches… it’s pricey, yes, but i think that shelly is pretty much similar priced. If nothing else these devices are great way to check out how devices are connected over all 3 phases and if any of phase is overloaded (and re-wiring is needed).
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Hi, I have the PZIOT-E01 device and have flashed it with OpenBKN but struggling to find what PINs information is needed for after flashing.
What PINs is the current measurement on etc? Also how are you parsing the information in home assistant to calculate the current etc?
Thanks!
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Hi,
were you able to use the PZIOT-E02 with ha?
As i described above the BL0942 is connect via SPI to the BK7231N, therefore you need to rewire the module to a UART connection to get it to work.
Thanks for the update, this is great news.
I have one more question:
Are you on net metering / can this device handle that?
net metering short explanation:
say that for one hour:
L1 - consumes 1kW from the grid
L2 - consumes 1kW from the grid
L3 - sends 3kW to the grid (solar production)
In net metering the meter will show:
usage: 0
export: 1kWh
Shelly 3em can’t do this - in this case it will show:
usage 2kWh
export: 3kWh
I’m not on net metering, since i don’t produce any electricity,i just monitor my consumption. But, yes, as far as i know iammeter does support net metering: https://www.iammeter.com/docs/net-energy-meter
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IMHO the information you described from Shelly is more complete than the “net metering” and you can still do the calculations with a very simple template sensor.
Why wouldn’t you prefer the Shelly in this case?
I might be missing something but that template is not that simple.
Shelly uses ade7880 which provides momentary power but also energy usage.
To do this math in template you need to check if sum of power across three phases is negative or positive and the integrate power over time.
The problem is you loose precision of the IC that does high frequency sampling.
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Somehow I’ve missed that in their doco. Thank you!
In stead of using 1x Shelly 3EM its possible measure 3f + N connection with 3x Shelly EM. If you have no solarpanels its possible to measure the powerusage just by adding the 3 power consumption parameters.
When you have solarpanels we need to use the kwh_returned parameter (available on the Shelly EM) on the fase where your solarpanels are connected.
Total_kwh_Usage = kwh_used_Line1 + kwh_used_Line2 + kwh_user_Line3 + kwh_PV_generated - kwh_returned_Line_PV_connected
This way the Total_kwh_Usage calculed value takes into account your power comsumption on the fase where your solarpanels are connected.