System Overview
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 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.
Current system

emonTx v4: A 6x circuit energy monitoring node. Transmits data via an inbuilt 433MHz radio to an emonBase. It can also send data via a Wi-Fi extension board or directly via USB.

emonVs v1.1:
Combined precision voltage sensor and power supply.

emonBase: A Raspberry Pi base-station that receives data sent from the emonTx4. Hosts the emonCMS software for full local data logging and visualisation capability. With new direct SPI RFM69 radio transceiver.

CT sensor: Current transformer. Used for measuring AC current. We use a non-invasive clip-on sensor for ease of installation and safety.

emonCMS: An open-source web application, for processing, logging and visualising energy, temperature and other data. Runs locally on the emonPi and emonBase, also available remotely via emoncms.org.
Earlier hardware

emonPi: An all in one 2 circuit energy monitor and base-station which collects data, hosts the emonCMS software and can also receive data from other sensor nodes.

emonTx V3.4: A 4 circuit energy monitoring node. Transmits data via an inbuilt 433MHz radio to an emonBase or emonPi. It can also send data via an ESP8266 WiFi adapter or directly by a serial connection.

emonTH: A battery powered, wireless, room based temperature & humidity monitoring node. Transmits data via 433MHz radio to an emonBase or emonPi.

ACAC Voltage sensor: An AC-AC Voltage adapter, used for measuring AC Voltage safely. Used in conjunction with the AC current measurement to calculate power consumption accurately.