Advice on a new system

Hi all,

I’d like to set up an OEM system in my house and garage (in the UK), but the situation is a little unusual:

  • I have solar PV but the panels are on the garage roof, not the house roof.
  • The garage is connected to the house by an underground cable. The main supply fuse and meter are in the house.
  • The garage is about 15m from the consumer unit at the far side of the house. The house is old, with thick brick walls, and it’s very unlikely that a 433MHz signal would make it between the two locations.
  • The garage has wired and wireless internet, thanks to a fibre I had buried alongside the mains connection.
  • I would like to add an OpenEVSE in the garage within the next year.

I definitely want monitoring in both the house and the garage, so that I can monitor overall import/export as well as generated PV power. The obvious combination of EmonPi in the house and EmonTX in the garage is unlikely to work because of the distance involved. Is there anything that can do a job like the EmonTX but just publish MQTT messages? (Assuming the EmonPi is a broker, and can gather data in this way?)

Any advice gratefully received.


I have something similar. I use EmonTX units with ESP modules transmitting over WiFi to a pi server running emoncms.

The emonTx can use an ESP8266 as @ian says to send data to your emonPi via your LAN. That would appear to be the most straightforward solution, unless of course you want to start monitoring individual circuits in the house, when the 2 channels of the emonPi get used up rather quickly. If that’s likely in the foreseeable future, then another emonTx in the house and a RPi running emonCMS (i.e. exactly like @ian’s setup) would be cheaper (you don’t even need an emonBase as you’re not going to be using the 433 MHz RFM).

Thanks both for the advice. Two EmonTx with ESP8266 and a RPi running EmonCMS sounds good. Shame the EmonTX come with 433MHz units I won’t be using! Is there any easy way to disable the 433MHz units to avoid cluttering the 433MHz band unnecessarily?

Not easy for a newcomer - it involves a programmer, but easy enough when you’ve got everything set up and you know how: edit the sketch to remove the offending commands, recompile and upload.

Ok, thanks. I’ve never delved into the OEM source (or indeed used an Arduino) but I’m an electronic engineer and experienced software developer, so I’m not sure whether or not I classify as a newcomer in that sense! I may come back to ask for more specific information once I have the hardware.

Please do. The additional hardware you need is a programmer from the shop, then you need to install the Arduino IDE and libraries Learn→Electricity Monitoring→Using the Arduino IDE

Ah well… I didn’t know that. In that case, you’re not. :+1:

My first instinct would be to test this hypothesis, hopefully proving it wrong. My garage is a lot further than 15 m and an emonTx has no problem transmitting from there to an emonBase in my house. Admittedly I don’t have brick walls and I did purchase a proper dipole antenna for the emonTx but the supplied antenna worked OK initially. A better antenna just improved the S/N somewhat.