Shelly has five energy meters in its range and, at a glance, they all seem to do the same thing. But choosing wrong is costly: a clamp that won't fit your cable, a single-phase unit in a three-phase install, or a meter with no relay when you needed to drive a contactor.
This guide compares the Shelly EM, the EM Gen3, the Pro EM-50, the Pro 3EM and the Pro 3EM-3CT63 using Shelly's official documentation.
Comparison at a glance
All five declare the same 1% measurement accuracy, so accuracy isn't a deciding factor. What decides are the phases, the maximum current, the relay and the clamp type.
How to choose in three questions
The order matters. Always start with the phases, then the maximum current, and leave the features for last. If your grid tail exceeds 63 A, the 3CT63 is ruled out no matter how much its size appeals to you.
Shelly EM: the veteran
Still a reasonable option for a single-phase home. Two measurement channels, a relay to drive a contactor and 365 days of internal memory, the longest history in the range.
Its weak point is connectivity: Wi-Fi only, no Ethernet or Bluetooth, and as a Gen1 device it supports neither scripting nor Modbus. It also needs an extra bracket for DIN-rail mounting.
Choose it if: you want to keep more than a year of history and don't need Bluetooth or on-device automations.
Shelly EM Gen3: the natural evolution
Same approach as the EM (single-phase, two channels, dry-contact relay) but with third-generation electronics.
It adds Bluetooth BLE (which makes setup much easier), mJS scripting for on-device automations, and DIN-rail mounting as standard with no extra bracket. Its compact form also fits in a wall box.
The only thing it loses against the Gen1 is memory: it stores far less history than the veteran's 365 days.
Choose it if: you want a current single-phase meter. For most new installs it's the more sensible of the two.
Shelly Pro EM-50: professional single-phase
Single-phase, two channels, in DIN-rail format, with Ethernet, Bluetooth and Gen2 firmware with scripting and Modbus TCP.
It has an integrated dry-contact relay (I and O terminals, max 2 A / 240 V) and keeps at least 60 days of data at one-minute resolution. Its limit: 50 A per channel.
Choose it if: you want a professional panel mount and a wired network connection.
Shelly Pro 3EM: the reference three-phase
DIN-rail three-phase with four clamp inputs (three phases plus neutral) and up to 120 A per phase. It's also the only Shelly meter compatible with Matter.
It includes 4-quadrant measurement, phase-sequence error detection, channel-by-channel calibration and a minimum-load threshold.
It has no relay: to drive a contactor you need the Shelly Pro 3EM Switch Add-on.
Shelly Pro 3EM-3CT63: when there's no space
It shares chassis and electronics with the Pro 3EM, but instead of three split clamps it uses the 3CT63: a single piece integrating all three phases, fitted directly over the breaker.
The trade-off is two limits: current drops to 63 A and the conductor opening is 9 mm.
The clamp defines the model
This is the practical difference most people overlook when buying. The clamps are not interchangeable between models: each meter is calibrated for its own current transformer.
FAQ
EM Gen1 or EM Gen3?
For a new install, the Gen3: it adds Bluetooth, scripting and DIN rail as standard. The Gen1 only pays off if you need to keep more than a year of history on the device itself.
Can I use a single-phase meter in a three-phase install?
Only if you're happy measuring one of the three phases. The EM, the EM Gen3 and the Pro EM-50 take the reference voltage from a single phase, so they can't correctly compute the power of the other two.
Can I fit a 120 A clamp on a Pro EM-50?
No. It's designed for 50 A transformers and its measurement range goes up to that.
Which ones speak Modbus?
The four Pro-range meters: the Pro EM-50, the Pro 3EM, the Pro 3EM-3CT63 and the Pro 3EM-400A. It's Modbus TCP over port 502.
Which one do I need for solar self-consumption?
They all measure in 4 quadrants, i.e. they tell import from export. In a single-phase home the EM Gen3 or the Pro EM-50 is enough; for three-phase, the Pro 3EM. We cover it in the guide on how to measure your solar self-consumption.
Which ones can cut the power or switch a load?
The Shelly EM, the EM Gen3 and the Pro EM-50 have an integrated relay. The two three-phase units need the Shelly Pro 3EM Switch Add-on. In every case the output drives a contactor: never wire the load directly.
Do they replace my utility meter?
No. They're monitoring meters, not certified billing equipment.
Quick summary
- Single-phase home, new install → Shelly EM Gen3
- Single-phase with very long history → Shelly EM
- Single-phase with DIN panel and Ethernet → Shelly Pro EM-50
- Three-phase with high currents → Shelly Pro 3EM
- Three-phase with tight space → Shelly Pro 3EM-3CT63
- Over 120 A per phase → Shelly Pro 3EM-400A
Still unsure? Send us your panel details (phases, contracted power and available space) and we'll tell you which one you need. Technical support and shipping available for your market.
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