Three-Phase 6-Channel Energy Monitoring: emonPi2

£263.58 (Inc. VAT)
£219.65 (Ex. VAT)
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This is a 3-phase electricity monitoring solution. See here for single-phase monitoring.

Note: the emonPi2 3-phase supports 4-wire 3-phase systems i.e with a Neutral wire, 3-wire 3-phase systems (without a Neutral) are not supported.

The emonPi2 is a combined 6 CT energy monitor and web-connected base station in a single unit. When used with the emonVS voltage sensor and a selection of CT sensors, it provides a complete electricity monitoring solution. This is ideal for monitoring home consumption, solar generation, EV charging, heat pumps, battery storage, or any AC electrical circuit.

The emonPi2 builds directly on the recent emonTx4 development, focusing on higher accuracy, more CT channels, precision voltage sensing, and the AVR-DB microcontroller core.

emonPi2 features:

Measurement board:

  • 6x clip-on CT current sensor inputs (suitable for a range of 333mV voltage output CT sensors)
  • Voltage input for use with emonVs precision voltage sensor (RJ45 connector)
  • Full Real/Active power measurement & continuous sampling
  • Cumulative energy persisted on reboot
  • Optional pulse counting and analogue voltage input
  • On-board USB-C to UART converter for easier programming and serial output
  • Handled by the Pi: DS18B20 temperature sensing (pluggable terminal blocks required)
  • Handled by the Pi: 433 MHz RFM69CW radio transceiver

Integrated base-station:

  • Raspberry Pi mini computer
  • Full local data logging and visualisation capability using emoncms.
  • Option to post data to a remote server such as
  • Data accessible via MQTT
  • Software support for reading from Modbus & M-BUS meters via USB


  • Wall-mount aluminium enclosure
  • Made in UK
  • UKCA & CE approved

emonVs features

The emonVs is a combined precision voltage sensor and power supply unit designed to be used with the emonPi2 for higher accuracy voltage measurement and a single socket or hardwire install.

  • Precision voltage sensor provides voltage signal for the emonPi2
  • Supports a range of mains voltages 120-240V, US, EU, UK
  • Single-phase as standard
  • 10W Power supply with ample power for the RaspberryPi integrated in the emonPi2.

CT current sensor selection

To obtain the highest accuracy we recommend choosing CT current sensors that match the current rating of the circuit being measured. 

E.g for 16A or 20A circuits choose the 20A CT sensor, for 32A or 40A circuits choose the 50A CT sensor and so on. No damage will be done if the current in the circuit exceeds the CT rating, the output will just be 'clipped' resulting in inaccuracy.

The physical size of the CT sensors is also proportional to the current rating which makes the smaller sensors very suitable for installation inside fuseboxes / consumer units.  See individual CT current sensor product pages for more information:

The standard 3-phase firmware allocates each phase to each CT input on the emonPi2 as follows:

  • CT 1: phase 1
  • CT 2: phase 2
  • CT 3: phase 3
  • CT 4: phase 1
  • CT 5: phase 2
  • CT 6: phase 3

Note: The emonPi2 requires voltage output CT sensors, it is NOT compatible with the old current output YHDC (blue) 100 A CT sensors.


There are a couple of things to consider when combining the emonPi2 with an existing system.

  • emonTx4 + 3phase RJ11 emonVs + emonBase: Is is currently not that straightforward to use an original RJ11 3-phase emonVs to provide a 3 phase voltage signal to both an emonTx4 and an emonPi2. We will be providing a RJ11 to RJ45 adapter to make this easier in early 2024. It would help us to know how much demand there is for this requirement. Please get in contact if you need this solution.
  • emonTx4 running compatibility firmware: The emonPi2 only supports the new LowPowerLabs encrypted radio format. Any existing radio nodes running JeeLib classic radio format will need updating to the LowPowerLabs format to be received by the emonPi2 integrated radio.
  • Replacing an emonPi v1: The emonPi2 can replace an emonPi v1, again any radio nodes running the JeeLib classic radio format will need updating to the LowPowerLabs format. The emonPi 1 AC-AC adapter voltage sensor and YHDC 100A CT sensors are not compatible as standard with the emonPi2. 


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