Let the Raspberry Pi Monitor Energy

If you are looking for monitoring energy remotely, an open source system that uses the ever-popular single board computer, the Raspberry Pi (RBPi) may be suitable. The company, OpenEnergyMonitor, makes the open-source tools for monitoring energy, and at present, they are using the RBPi3. According to their co-founder Glyn Hudson, the aim of OpenEnergyMonitor is to help people understand and relate to how they use energy from their energy systems, and the challenges of sustainable energy.

The system uses five main units. Users can assemble and configure these to work in a variety of applications. Both hardware and software in the system is fully open-source, and the hardware is based on Arduino and RBPi platforms. Users can opt to use the system for monitoring home energy, monitoring solar PV, and or monitoring temperature and humidity.


When configuring the OpenEnergyMonitor system, emonPi, as a simple home energy monitoring system, it allows measuring the daily energy consumption and analyzing real-time power use. The all-in-one energy-monitoring unit, emonPi is a simple installation based on the RBPi, requiring only an Ethernet or Wi-Fi connection at the meter location.

Clip-on CT sensors on the emonPi enable it to monitor independently two single-phase AC circuits simultaneously. While the emonPi can monitor temperature, it has an optical pulse sensor to interface directly with the utility meters, which means the emonPi has to be installed next to the utility meter.

The emonPi comes with Emoncms, the open-source web application. This helps in logging and visualizing energy use along with other environmental data such as temperature and humidity. It has two power outlets and requires Ethernet or Wi-Fi to transfer data. The RBPi operates on a pre-built OS on an SD card included with the energy monitor. The 5 VDC power required has to be fed in from an external power supply unit.

As power is the product of voltage and current, the emonPi requires an AC-AC voltage sensor adaptor and a clip-on CT sensor. While the emonPi comes with one CT sensor as standard, it can accept two CT sensors.


For remote monitoring, users can use emonTx, a remote sensor node as an alternative to emonPi. The emonTx runs as a standalone unit, with an ESP8266 Wi-Fi module running EmonESP. This can post directly to Emoncms without using emonPi or emonBase.

Users can monitor a maximum of four single-phase AC circuits with the clip-on CT sensors using the emonTx. A plug-in AC-AC adaptor powers the unit, and provides the AC voltage sample, which the emonTx uses for real-time power calculations. If AC power is not available, emonTx can be powered using four AA type batteries.

Optional LED Pulse Sensor for Utility Meter

This sensor allows interfacing directly with utility meters that have LED pulse output. It is compatible with emonTx and emonPi, and reports the exact amount of energy as the utility meter does. Although best used together with clip-on CT sensors, the LED pulse sensor cannot measure instantaneous power.


This is a web-connected gateway, consisting of an RBPi and RFM69Pi RF receiver board. It receives data via a low power RF carrier at 433 MHz from emonTx or emonTH and offers local and remote data logging using Emoncms.