Shelly's Pro range of meters shares a common format: four units of 94 × 19 × 69 mm for DIN rail, all with Wi-Fi, Ethernet and Bluetooth, 4-quadrant measurement, Class B accuracy and Modbus TCP. Sitting on a shelf, they look identical.
The differences are in three places: how much current they measure, which clamp they use and whether they can act on a load. This guide compares the Pro EM-50, the Pro 3EM, the Pro 3EM-3CT63 and the Pro 3EM-400A.
The four at a glance
What does not set them apart: all four mount on DIN rail, run on 110 to 240 V, draw less than 3 W, measure in 4 quadrants, speak Modbus TCP and offer Wi-Fi, Ethernet and Bluetooth. Connectivity, protocols and accuracy are not deciding factors within this range.
Start with the current
It's the decision that rules out models before any other. If your supply demands more amps than the unit can handle, it doesn't matter how well it fits everything else.
The scale covers from 50 A up to 400 A per phase. For reference: single-phase, 50 A is around 11 kW; three-phase, 63 A is around 43 kW of contracted power.
Don't size to the limit. If your supply is exactly 63 A, the 120 A model leaves you headroom for future expansions without changing the unit.
Shelly Pro EM-50: the only single-phase model
Two independent measurement channels of up to 50 A each. It's the only one in the Pro range that has a built-in relay: a dry contact on terminals I and O, with a maximum of 2 A at 240 V.
That difference matters more than it seems. The three three-phase models need the Shelly Pro 3EM Switch Add-on to drive a contactor, which adds cost and space.
It stores at least 60 days of history at one-minute resolution.
Choose it if: your supply is single-phase, you want to measure two circuits separately and you need to act on a load without extra accessories.
More detail: installation guide and sub-metering use case.
Shelly Pro 3EM: the reference three-phase meter
Four clamp inputs (IA, IB, IC and IN) and up to 120 A per phase. The neutral clamp is optional and not included.
It's the only Shelly meter compatible with Matter, which makes it easier to integrate into smart-home ecosystems without going through Shelly's cloud.
Two details to bear in mind: phase C powers the unit as well as being one of the measured phases, and its history is the shortest in the range at at least 45 days.
Its practical weak point is the clamps: three 120 A CTs take up quite a bit of room and don't always fit in a panel that's already full.
Choose it if: you have three-phase, currents of up to 120 A and enough space in the panel.
More detail: installation guide and phase-imbalance detection.
Shelly Pro 3EM-3CT63: the answer to space
Same electronics as the Pro 3EM, but the clamp changes completely. The 3CT63 is a single 14 × 54 × 26 mm piece that integrates the three phases and mounts directly over the circuit breaker.
In exchange for the space it saves, two limits: 63 A per phase and a conductor opening of Ø9 mm. That second figure is what generates the most returns, so measure it before you buy: it's the outer diameter of the insulated cable, not the cross-section in mm².
It stores up to 60 days of history, more than the Pro 3EM.
Choose it if: you have three-phase, the panel is tight on space and you don't exceed 63 A.
More detail: installation guide, use case in crowded panels and frequently asked questions.
Shelly Pro 3EM-400A: for large installations
It raises the ceiling to 400 A per phase, well above the rest. It's designed for industrial units, substations, distribution centers and photovoltaic plants of a certain size.
It adds an optical pulse indicator for visual tracking of consumption and stores 60 days of data at one-minute resolution.
Choose it if: your installation exceeds 120 A per phase.
The decision tree
The order of the questions matters: first the phases, then the current, and only at the end the available space and the features.
Frequently asked questions
Which ones can cut or switch on a load?
Only the Pro EM-50 has a built-in relay. The three three-phase models need the Shelly Pro 3EM Switch Add-on. In every case the output drives the coil of a contactor: never connect the load directly.
Do they all speak Modbus?
Yes. All four support Modbus TCP over port 502, in addition to MQTT and RPC. It's a feature of the range, not a differentiator between them.
Are the clamps interchangeable between models?
No. Each unit is calibrated for its current transformer. Fitting a clamp from another model gives readings scaled by the wrong factor.
Can I use a three-phase model on a single-phase installation?
The Pro 3EM and the Pro 3EM-3CT63 support single-phase wiring, although if you only have one phase the Pro EM-50 usually works out better.
Are they good for solar self-consumption?
All four measure in 4 quadrants, so they distinguish what you import from what you feed back to the grid. We explain the approach in the guide on how to measure your solar self-consumption.
Do they replace my utility meter?
No. They're monitoring units, not certified billing meters. Their accuracy is more than enough to optimize and automate, but it has no legal validity against your electricity retailer.
How much history do they store?
Between 45 and 60 days at one-minute resolution, in non-volatile memory and exportable to CSV and JSON. All have a real-time clock, so timestamps stay correct even if the internet goes down.
Summary
- Single-phase with load control → Shelly Pro EM-50
- Three-phase up to 120 A, with Matter → Shelly Pro 3EM
- Three-phase with no space in the panel → Shelly Pro 3EM-3CT63
- High-power installations → Shelly Pro 3EM-400A
Looking for a meter for a home and don't need DIN rail? Check the general comparison of Shelly meters, which also includes the Shelly EM and the EM Gen3.
Unsure about your installation? Write to us with the phases, contracted power and free space in your panel and we'll tell you which one fits. Technical support in English and shipping from Spain.
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