Device overview
Shelly Pro 3EM-400 is the 400 A CT package of Shelly's Pro 3EM DIN-rail energy meter. It is intended for higher-current homes, multi-dwelling units, light commercial panels, agricultural buildings, and other installations where a smaller CT package may not fit the service or feeder being monitored.
The device should be treated as an energy meter, not as a solar inverter, battery, EV charger, or standalone gateway. Its role is to measure electricity flow and expose that data through Shelly's app, embedded web interface, local network protocols, and automation systems such as Home Assistant.
Core metering features
The Pro 3EM-400 measures accumulated energy plus real-time voltage, current, active power, and apparent power per phase. Shelly positions the 400 A package for three-phase and single-phase installations, with support for multiple connection types, phase-sequence detection, data logging, and 4-quadrant measurement.
For comparison and filtering, the important scalar is the included 400 A CT package. The device includes three 400 A current transformers for phase measurement and also provides a fourth CT input for neutral-current measurement when that wiring approach is required.
Installation and electrical fit
Installation is DIN-rail based and should be handled by a qualified installer. The device has line inputs for three phases plus neutral, CT inputs for phase and neutral measurement, and an Ethernet port for wired LAN connectivity. Shelly also documents Wi-Fi and Bluetooth connectivity.
This page records phase support as three-phase or single-phase because Shelly documents multiple connection types and single-phase monitoring use cases. For buyers, the key decision is whether the 400 A CT package is the right physical and electrical fit for the service conductors being monitored.
Local control and integrations
Shelly Pro 3EM-400 can run standalone on a local LAN or Wi-Fi network using its embedded web interface and local protocol options. Shelly documents MQTT, HTTP, WebSocket/RPC, TLS support, and Modbus-oriented integration behavior for the Pro 3EM family. Shelly Cloud remains useful for remote app access and cloud automation, but it is not required for local monitoring workflows.
Home Assistant support is recorded because Home Assistant's official Shelly integration supports Shelly devices through local discovery and setup. This makes the Pro 3EM-400 a strong fit for users who want local energy data in a broader automation system.
Solar and import/export monitoring
Shelly lists the Pro 3EM-400 as photovoltaic ready and documents 4-quadrant measurement. That matters for solar users because the meter can help distinguish imported and exported energy rather than only showing one-way consumption. It does not replace an inverter-approved meter where a specific inverter ecosystem requires one, but it is useful for independent monitoring, dashboards, and automation based on measured power flow.
Strengths and limitations
The main strengths are the 400 A CT package, LAN plus Wi-Fi connectivity, local protocol support, Home Assistant compatibility, and source-backed Class B / 1 percent active-energy accuracy claim. The main limitations are that it is still a CT-based monitoring device rather than a utility billing meter, contactor control requires the relevant Shelly add-on, and regional electrical approval or installer acceptance should be checked before using it in a specific panel.