A three-phase installation has a problem that shows neither on the bill nor on the meter: imbalance between phases. One phase can run at its limit while the other two are half empty, and the result is breaker trips, losses, and contracted power that goes unused.
You only see it measuring all three at once
A panel that has grown over the years nearly always ends up unbalanced: each new circuit goes on whichever phase was nearest to hand. With all three phases’ data in front of you, rebalancing is a matter of moving a few circuits — and the result is fewer trips, fewer losses and, often, more out of the power you already pay for.
The Shelly Pro 3EM measures the three phases and neutral simultaneously, which is exactly what it takes to see it.
What it reports
It measures in four quadrants and, for each phase, reports voltage, current, active and apparent power, active and apparent energy, power factor, and fundamental active and reactive energy.
Three features set it apart from a domestic meter:
- Phase-sequence error detection: it warns if the A → B → C order is wrong.
- Per-channel calibration, to match the response of the three channels.
- Minimum-load threshold, so it does not accumulate energy when what it measures is noise.
It keeps at least 45 days at one-minute resolution, exportable to CSV and JSON, with a real-time clock.
Where it fits
- Warehouses and workshops. Finding which machine causes the peaks, and adjusting the contracted power.
- Hotels and buildings. Watching consumption by zone and finding what gets left on.
- Farms. Pumping and irrigation, where three-phase motors account for the spend.
- Three-phase self-consumption. Measuring in four quadrants, it tells import from export.
Up to 120 A, and Matter
It takes 120 A per phase — only the Pro 3EM-400A goes higher — and it is the only Shelly meter that supports Matter, which lets it join a home-automation system without going through Shelly’s cloud. Wi-Fi, Ethernet and Bluetooth, each of which can be enabled separately.
To act on anything, you need the add-on
Unlike the Pro EM-50, the Pro 3EM has no relay. To drive a contactor — starting a pump when there is spare solar, for instance — add the Shelly Pro 3EM Switch Add-on.
The add-on’s interface sits at mains voltage while the device is powered. Always connect it with the power off.
What you need
- A Shelly Pro 3EM and one free module on the DIN rail.
- Three 120 A clamps, and a fourth for neutral if you want to measure it — not included.
- Real room in the panel: 120 A clamps are bulky. If it is tight, the Pro 3EM-3CT63.