In a three-phase installation there's a problem you can't see by looking at the bill or the meter: phase imbalance. You can have one phase at its limit while the other two run half-empty, and the result is breaker trips, losses and wasted capacity.
The Shelly Pro 3EM measures the three phases plus the neutral simultaneously, so imbalance stops being invisible.
The problem you only see by measuring all three at once
A panel that has grown over the years almost always ends up unbalanced: circuits get hung off whichever phase was closest to hand. With the data for all three phases in front of you, redistributing loads is a matter of moving a few circuits.
The benefit is direct: fewer trips, fewer losses and, in many cases, being able to make better use of the power you already have contracted.
Exactly what data it gives you
The Pro 3EM measures in 4 quadrants and reports, for each phase: 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, which warns you if the A → B → C order is altered.
- Channel-by-channel calibration, to equalize the response of the three channels.
- Minimum-load threshold, which avoids accumulating energy when the consumption is pure noise.
It stores at least 45 days of data at one-minute resolution, exportable to CSV and JSON, with a real-time clock that keeps timestamps correct even if the internet goes down.
Where it fits
Shelly's documentation aims it at residential installations with a three-phase supply, apartment buildings, hotels, shops, farms, municipal installations and educational centers.
Some specific scenarios where we see it work well:
- Warehouses and workshops. Identify which machine triggers the power peaks and adjust the contract.
- Hotels and buildings. Monitor consumption by zone and detect equipment left running.
- Farms. Pumping and irrigation control, where three-phase motors dominate the cost.
- Three-phase self-consumption. By measuring in 4 quadrants it distinguishes what you import from what you feed back to the grid.
Up to 120 A and Matter-compatible
With 120 A per phase it handles the most current in the range (below the Pro 3EM-400A, which is on another level), and it's also the only Shelly meter compatible with Matter, which makes it easier to integrate into smart-home ecosystems without depending on Shelly's cloud.
Connectivity via Wi-Fi, Ethernet and Bluetooth, each one enabled separately.
To control loads you need the add-on
An important difference from the Pro EM-50: the Pro 3EM has no relay. If you want it to act on a contactor (for example, starting a pump when there's surplus solar energy), you need to add the Shelly Pro 3EM Switch Add-on.
That interface is at high voltage while the unit is powered, so always connect it with the power off.
What you need
- A Shelly Pro 3EM and a free module on the DIN rail.
- Three 120 A clamps (plus an optional fourth for the neutral, which isn't included).
- Actual space in the panel: the 120 A clamps are bulky. If you're tight, consider the Pro 3EM-3CT63.
We detail the installation in the Pro 3EM installation guide, and the choice between models in the comparison of Shelly meters.
Want to know if your installation is unbalanced? Write to us with your panel details and we'll point you in the right direction. Technical support in English and shipping from Spain.
