Heatpump Monitor Update

This is an update on progress on the heatpump monitor I posted about last December here: Heatpump Monitoring board MBUS, ESP12++ | Archived Forum

The hardware is now in its second revision and the EmonESP WIFI software is working well. It is still a through hole kit that requires assembly and firmware upload, the long term plan is to integrate many of the heatpump monitor features in a future version of the EmonTx v3 but this is some way off yet, see further development.

I have developed the heatpump monitor with the help of John Cantor of heatpumps.co.uk who I have been working with on heatpump monitoring for some time. Over the last almost 8 months of development and testing we’ve gained a lot of very useful data from using the monitor on our own systems and others, an example of which can be seen in the video linked below.

The full detail of the current state of development can be found on the github repository here:

The main features are:

  • CT current and ACAC voltage based electricity monitoring
  • Pulse counting or IRDA Elster meter reader
  • Analog inputs for Vortex Flow Sensor (VFS) option (e.g Sika, Grundfos)
  • MBUS reader for kamstrup heat meters
  • 4x individually broken out DS18B20 temperature sensor connections
  • Arduino ATmega328 core
  • Connectivity options: ESP-12 WIFI, RaspberryPI header, RFM69

The kit will be available in the OpenEnergyMonitor shop soon as a development kit. The cost for a full kit is currently coming to £51.76 ex VAT (£62.11 inc VAT) and without the case £40.6 ex VAT (£48.72 inc VAT). The full detail of what’s included and costing can be found here:
Github: Heatpump Monitor Bill of Materials and costing

The build outline, installation and setup notes can be found here:

This video gives an idea of what you can see, the kind of data and understanding that you can get out of the monitor with it all up and running:

Thoughts on open hardware
I really enjoyed going through the end to end process of developing the heatpump monitor, starting with an idea that it would be possible to bring all the different components together needed for heatpump monitoring all on one board and then going forward and designing, prototyping and building this idea. For anyone else thinking of doing something similar I would really recommend it. I’ve published transparent costing for this board (both in 1x and 20x) to give some insight into how that side of things works and will be documenting how to get the PCB manufactured with Ragworm and fascias laser cut at a local FabLab.

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One of the interesting outcomes of the costing exercise is that the cost price in 1x is pretty much the same as the kit sale price including the margin. Which means that if you are interested in developing a piece of hardware and getting a custom pcb made, even if just for your own use, you are not necessarily at a financial disadvantage, especially if you have a good stock of resistors, capacitors, atmegas as esp modules which are useful across multiple projects.

Cut down energy monitor kit
The other thing to note is that the board can be used as a ESP8266 WIFI enabled electricity monitor for home energy monitoring or solar pv monitoring. The MBUS reader and quite a few other components can be left off the board. There are build notes for this here: Github: Energy Monitor Build and example firmware BasicEnergyMonitor

We will likely be doing a build workshop at the September EcoHomeLab in Manchester for this if anyone is interested.

A key consideration when planning a heat pump monitoring installation is choosing the right heat meter. John Cantor has written a blog post outlining the importance of selecting the right heat meter in order to minimise the pressure drop across the heat meter which can be read here

Selecting the right heat meter

Temperature Sensing
Another post worth highlighting is John’s post on temperature sensing in particular mounting the temperature sensors to pipework or within a pocket in order to get a good liquid temperature measurement:

The 3rd revision of the heatpump monitor board is now being made thanks to Ragworm. With additional voltage regulator options. Schematic and board files are available here: https://github.com/openenergymonitor/HeatpumpMonitor/tree/master/Hardware/v3

In the next revision I hope to explore using the ATM90E26 special metering chip for higher accuracy with the help of Tisham Dhar who has been exploring this option, documented on his blog here:

The design will likely move to SMT at this point.

EcoHomeLab workshop: (Manchester) 8th September Im also going to be doing a workshop at the next EcoHomeLab in Manchester on building an open source energy monitor using the home energy monitoring cut down kit version of the board, more info here: http://www.meetup.com/Eco-Home-Lab-Manchester/events/233285719/


Happy to announce that the Heatpump Monitor is now available in the OpenEnergyMonitor shop as a development kit! The shop entry can be found here:


The hardware is now in its fourth revision with only a minor modification from v3 which has been much more stable after the addition of the higher current voltage regulator.

All documentation, schematics and board files can be found in the Heatpump Monitor github repository:


1. Packaged kit

2. Core kit of components

3. Assembled board

4. With enclosure

This is an advanced kit that requires assembly, soldering and firmware upload and is being made available in its current form as a development kit for those comfortable with electronics assembly and Arduino + ESP8266 programming. The kit does provide one of the lowest cost routes to a web connected WIFI enabled energy monitor at £36.40 ex VAT (£43.68 inc VAT) - price without the MBUS heat meter reader components and enclosure. If your on a tight budget and enjoy a bit of soldering this could be a good kit for you.

An alternative approach to ESP8266 WIFI energy monitoring with much less assembly required could be to use an EmonTx v3 with an ESP8266 Huzzah WIFI module.

There is also the neat IotaWatt project by @overeasy with ESP8266 feather board and ADC shield - which is a really interesting approach.

Just come across this. Very useful indeed. Perhaps add it to the shop page?

Good point @borpin, I’ve added the link both to the shop page and github readme. Thanks!

i always found taking aluminium foil (household ) and wrapping it tightly around a copper/plastic pipe and sensor . and then insulating it works really well. as the aluminium has a quicker response time to temperature changes due to its lighter mass…

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When uploading firmware via Arduino IDE,

what board should i select? What settings should I change to get Kamstrup 402 data trough M-Bus…

Hello @Boye

The settings are:

#define KAMSTRUP_MODEL 402


#define MBUS_ENABLE 1


I’m very interested in this monitor but it seems it’s no longer available. Are there plans to make more kits available, or can i purchase somewhere else?
If not, is there a suitable alternative i can buy / build?
Many thanks

Welcome, Vaughn, to OEM.

You didn’t know where to look! I happened to remember seeing this posted only days ago:
Advices about HeatPump Monitor - #12 by TrystanLea

Indded, I did miss that one! Thanks for the pointer!


This certainly looks like the monitor for me. @TrystanLea, now that the government seem to be supporting heat pump monitoring I wonder if there is an approved company that would do the actual monitoring based on the use of your controller? I like the idea of an expert doing the monitoring but don’t want a proprietary monitor or closed data. (It’s bad enough having to go with a proprietary ASHP but I didn’t have sufficient chops for a DIY like yours.)