Do i understand clearly what i need?

I discover your offering and i gave a look to your website.
My needs : to monitor my global use of electric power, monitor the production of my solar panels, and monitor some dedicated electrical use that i have in my house.
Based on that i understand that i could buy :

  • EmonTX V3 with the 4 AC sensors, 1 for the outside power link, 1 for the solar panels array, and 2 for 2 dedicated internal circuits
  • ESP8266 Wifi energy monitor in order to connect the EmonTx to my WiFi network
  • EmonCMS which i could download and install on a Linux partition on my Windows 10 desktop

Then can i add others EmonTx V3 if i want to mintor other dedicated circuits inside my house ? All circuits being monitored in the main electrical panel where the other EmonTx and the ESP8266 are located.

Do i have a correct understanding ?

Or do i need top buy other components ? and which ones and for what ?

Welcome to the OEM forum, Bernard.

My first question is: Will your Windows machine and the Linux VM be running continuously all day every day? Because it must do to store the data. The emonTx does not save any of the data at all - once it is transmitted, it is gone. If the data is lost en route, it is lost forever.
If the answer to that is no, then I suggest a Raspberry Pi on which you run emonCMS.

Do you have a single phase or a three-phase supply? If it is three-phase, then you will need much more than 1 emonTx. But if you only have one phase, then I think what you suggest should work. You will need a 5 V USB power supply as well as the a.c. adapter if you have the ESP8266 added to your emonTx, and I strongly suggest you buy a programmer also.

Thks for the feedback.
I understand for the Linux, and i have a Pi3 available or i can, buy one and dedicate it to the collect of data. Got it.

I am 3 phases, but will change it for 1 phase in the next coming weeks. So 1 emonTx with 4 sensors will be ok, for the start, ESP8266 will ensure the transmission of data to the Pi3 ? But u say : nuy a programmer also…

May be u mean that the normal solution, not needing programming, would be to buy the emonbase + emontx if i need more than 2 sensors ? And then i would have all needed sensors, data colelction and aggregation, and web interface to visualize the date through my local network ? ANd here i don’t need to use a separate Pi3…

But i am unclear about the differences between EmonBase and EmonPi, why such a big price difference between these two options, there should be many important differences which a can’t understand very well…

A programmer is insurance. With it, you will be able to set up and adjust your emonTx if that is necessary, or check that it is working correctly.

I don’t think you need an emonBase. Let me explain:

The Raspberry Pi can use WiFi. It can receive data via WiFi or via an Ethernet connection or via a direct serial connection. It runs emonCMS software under Linux, and makes the graphs & dashboards available to a web browser via your LAN, either Ethernet or WiFi.

The emonPi is a Raspberry Pi with a 2-channel version of the emonTx all in one box. It can transmit and receive on the ISM radio frequency at 433 MHz as well as WiFi.

The emonBase is a Raspberry Pi but with only the ISM radio, it cannot monitor power, but it can receive data from a number of emonTx’s via ISM or via WiFi. It also runs emonCMS.

The emonTx has an ISM radio built in. You want to add WiFi with the ESP8266.

Therefore according to your original suggestion, you only need a Raspberry Pi (or another server) to run emonCMS, you don’t need the ISM radio that the emonBase gives you.

Here I think are your options. All are for single phase:

1. An emonPi: It will measure Grid and PV power, and your total house consumption is the sum (or difference) of those two powers. You cannot measure any other circuits.
I think you can buy this as all the parts without the Raspberry Pi, and use your Pi3.
If or when you want to measure individual circuits, you add an emonTx, and use the inbuilt ISM radio.

2. A Raspberry Pi + emonTx + ESP8266: This is almost your suggestion, but using your Pi3 instead of your desktop computer. The emonTx will measure Grid, PV + 2 more circuits, send the data to the Raspberry Pi via the ESP8266 & WiFi.

3. An emonBase + emonTx: If the ISM radio works in your house, this will do the same as No.2 but not needing the ESP8266. The dashboards & graphs of emonCMS are still available via your network. You would use your Pi3 and add the RFM69Pi ISM radio module that converts it into an emonBase.

I am sure there are a few more combinations that would work, and I hope I have not confused you too much.

@bemo47 If you can co-locate the Pi and the EmonTX this is possibly the cheapest solution.

@Robert.Wall, are there any instructions anywhere on setting up an EmonTX / RPi direct serial combo? It occurs to me that the original reason for the RF system (other than linking EmonTH data as well) was partly that Pis did not have on board WiFi.

More to the point, I believe the Pi can accept many direct serial connections - I don’t know the details, I think Paul (@pb66) knows.

The information for one serial connection is here:

Glyn & Trystan could tell us, but I think it was a natural progression from the NanodeRF and the Open Kontrol Gateway for Ethernet access to, that is, retaining the ISM 433 MHz link from scattered sensor nodes (emonTx / emonTH) to a “base station”.

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Ah that was the link I was after. Yes I realise a Pi can do more than one connection, but as an alternative for an ESP module (flashing etc) a PiZeroW running emonhub and direct serial connection could be a good solution.

hmmm, yes, yes, tha’s clearer…

just one point, about programmer, just for u to understand my ignorance (despite my 40 years of IT backgound…)… i thought u were saying to buy time from a “programmer”, a human doing programming… haha… ok… i see now that programmer for u, is a tool to help managing in some way the emonTX… not clear how but at least i understand what it is…

for the rest its now clearer, yes, and thanks

one more point, u say : “if ISM radio works in your house” … Is there any risk about ISM radio inside houses ? or only when emonBase and emonTX are not located close from each other ? if they are close each other ISM should work fine i hope…


If you have thick stone walls, or concrete walls or floors, or insulation with aluminium foil on one side, it can have problems. But then WiFi can also have a problem with those materials. In most houses, it works fine. The range is claimed to be about 100 m over open ground.

If we’re speaking of a wired RS-232 connection, then the Pi, like any other RS-232 device,
can handle only one serial device at a time.

That’s what I thought - without anything extra. But I think I read somewhere a suggestion to use a Serial - USB adapter - which is effectively what our programmer is.

That would work. One adapter for each RS-232 port would enable, as you alluded to earlier,
“multiple” serial connections.

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