Switch branches/tags
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
388 lines (364 sloc) 24.6 KB
layout title description date sidebar comments sharing footer published
System Overview
Getting started with OpenEnergyMonitor
2014-12-18 22:57

Next step: Connect »

The OpenEnergyMonitor system has the capability to monitor electrical energy use / generation, temperature and humidity.

The system is made up of five main units. These can be assembled and configured to work for a variety of applications. The system is fully open-source, both hardware and software. All hardware is based on the Arduino and Raspberry Pi platforms:


Please select the type of system you are interested in:

  1. Home Energy Monitoring
  2. Solar PV Monitoring
  3. Temperature & Humidity

The OpenEnergyMonitor system can be used as a simple home energy monitoring system for analyzing real-time power use and daily energy consumption.

The hardware options to set up a home energy monitor are as follows:


The emonPi is an all-in-one Raspberry Pi based energy monitoring unit making for a simple installation where Ethernet or WiFi is available at the meter location.

The emonPi can monitor two single-phase AC circuits using clip-on CT sensors. The emonPi can also monitor temperature, and interface directly with utility meters via an optical pulse sensor.


  • Raspberry Pi-based energy monitor
  • Local & remote data logging with Emoncms, our open-source web-app for processing, logging and visualising energy and other environmental data, such as humidity and temperature
  • Requires WiFi / Ethernet plus 2 x power outlets
  • Requires pre-built SD card image (included)

Sensors Required:

Power Adapters Required:

View in Shop →

emonTx (optional)

The emonTx is a remote sensor node. Data is transmitted to an emonPi or an emonBase via a low power 433MHz radio.

Note: as an alternative option, the emonTx can be used ‘standalone’ with an ESP8266 WiFi module running EmonESP to post directly to Emoncms without an emonPi / emonBase. See Using the EmonTx v3 with the ESP8266 Huzzah WIFI module

The emonTx can monitor up to four single-phase AC circuits using clip-on CT sensors. A plug-in AC-AC adapter can be used to power the unit and provide an AC voltage sample for real-power calculations. 4x AA batteries can be used to power the emonTx if AC power is not available.


  • Energy monitoring add-on node
  • Optional add-on if more than two circuits need to be monitored or if WiFi / Ethernet connectivity is not available at the location of the utility meter
  • RF Range is approximately similar to home WiFi and can be affected by obstacles e.g. thick stone walls
  • Up to 2x emonTx can be connected to a single emonPi
  • To connect an emonTx see: Setup > Adding Energy Monitoring Node

An emonTx can be powered by 3 x AA batteries; however, if possible, it is recommended to power the unit with an AC-AC adapter to provide an AC voltage reference for more accurate Real Power and VRMS calculations.

View in Shop →

Optical Utility Meter LED Pulse Sensor (optional)

  • Optional add-on sensor for interfacing directly with utility meters
  • Compatible with all utility meters with LED pulse output
  • Compatible with emonPi & emonTx (one pulse sensor per unit)
  • Reports exact amount of energy (Wh) reported by utility meter
  • Cannot measure instantaneous power
  • Best used in conjunction with clip-on CT sensor(s)

View in Shop →

emonBase (alternative to emonPi)

  • Web connected gateway: Raspberry Pi + RFM69Pi RF receiver board
  • No on-board energy monitoring functions
  • Receive data via low power RF (433Mhz) from emonTx or emonTH
  • Local & Remote Emoncms data logging
  • Runs the same software stack as the emonPi
  • No LCD screen to display local IP address or shut-down button
  • Knowledge of SSH highly desirable
  • Requires pre-built SD card image (optional extra)

View in Shop →

The emonPi and emonTx are designed to monitor single phase AC up to 100A. The system can work for some set-ups in the USA with some changes to the configuration. See user guide section Use in North America.

The emonPi / emonTx have been designed for single-phase AC monitoring. The emonTx can monitor ‘approximate’ 3 phase (assuming balanced phases) using modified firmware and 3x CT sensors + 1 x AC-AC adapter. Further reading

View hardware comparison table