Device overview
The OpenEnergyMonitor emonPi3 is an all-in-one 6-channel AC electricity monitor with an integrated Raspberry Pi and local emonCMS base-station role. It is a strong fit for technically confident homeowners, installers, and energy-data users who want local dashboards, MQTT access, expandable OpenEnergyMonitor sensors, and a more configurable monitoring stack than app-only consumer monitors.
Core monitoring features
The emonPi3 provides six CT sensor inputs and uses an emonVs voltage sensor / power input for real active-power measurement. The official shop positions it for simple single-phase homes through to 3-phase 4-wire monitoring, with use cases including home consumption, solar generation, battery storage, EV charging, and heat pumps.
Installation and CT setup
The device is wall-mounted and configured with voltage-output CT sensors selected to match the circuits being monitored. The official shop currently lists CT choices up to 200 A for each of the six CT input positions. The 3-phase shop option is for 4-wire systems; buyers with 3-wire Delta or other non-standard supplies should verify fit before ordering.
Local data and integrations
emonPi3 is local-first. It runs emonCMS locally, can expose data via MQTT, and can optionally post to remote servers such as Emoncms.org. Home Assistant fit is strongest through Emoncms or MQTT workflows rather than a closed vendor-cloud app model.
Strengths and limitations
The main strength is data ownership and flexibility: local emonCMS, MQTT, open-source hardware/software context, and expandable OpenEnergyMonitor nodes. The tradeoff is setup complexity. It is less plug-and-play than consumer app monitors, and the site should not present it as a billing-grade meter unless OpenEnergyMonitor publishes a formal accuracy-class source for this exact device.