Shelly Pro 3EM (120A) - 3-Phase Smart Energy Meter Review

The Shelly Pro 3EM is a DIN-rail mountable energy meter designed for both residential and light commercial use. Unlike basic plug-in monitors, this device installs directly into your consumer unit (fuse box) to measure electricity flow across three phases or three separate single-phase circuits. It features both Wi-Fi and LAN connectivity, ensuring stable data transmission even in metal enclosures, and supports local data storage for up to 60 days. It is 'Solar Ready', meaning it can measure net metering, tracking both energy consumed from the grid and energy exported by PV systems.

In a UK domestic setting, this device excels at identifying 'vampire' loads and monitoring heavy-duty appliances like heat pumps or EV chargers. Users report the LAN connection is a significant upgrade over the standard Shelly 3EM, preventing data drops in garages or plant rooms where Wi-Fi is weak. The responsiveness via the Shelly app is excellent, providing real-time voltage and amperage readings that help diagnose circuit imbalances or unexpected spikes in usage.

The device itself does not save energy, but the insights it provides can lead to significant reductions. In a typical UK home, identifying a single misplaced immersion heater timer or a faulty appliance could save £50–£100 annually. For solar owners, the real-time export data allows for 'load shifting'—running high-drain appliances only when solar production is peaked—potentially reducing grid dependency by 10-15%. Savings are entirely dependent on user action following data analysis.

This is not a DIY product. Installation involves fitting 120A current transformers (CT clamps) around live mains cables inside the consumer unit and wiring the unit to breakers. A qualified electrician is required to ensure safety and compliance with UK BS 7671 wiring regulations.

Negligible. The unit consumes less than 3W of power, costing roughly £7–£9 per year to operate based on current UK price caps.