Shelly has five energy meters in its catalog and, at a glance, they all seem to do the same thing. But choosing wrong is expensive: a CT clamp that doesn't fit around your cable, a single-phase unit on a three-phase installation, 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 data from Shelly's official documentation.
Comparison at a glance
All five declare the same 1% measurement accuracy, so accuracy is not a deciding factor. What decides is the number of phases, the maximum current, the relay and the type of CT clamp.
How to choose in three questions
Order matters. Always start with the phases, then the maximum current, and leave the features for last. If your supply exceeds 63 A, the 3CT63 is ruled out no matter how much its size appeals to you.
Shelly EM: the veteran
It is still a reasonable choice 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 whole range.
Its weak point is connectivity: Wi-Fi only, no Ethernet or Bluetooth, and being 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 do not 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 commissioning much easier), mJS scripting for automations run on the device itself, and DIN-rail mounting out of the box with no extra bracket. Its compact format also lets you install it in back boxes.
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 an up-to-date single-phase meter. For most new installations it is the more sensible of the two.
Shelly Pro EM-50: professional single-phase
Single-phase, two channels in a DIN-rail format of 94×19×69 mm, with Ethernet, Bluetooth and Gen2 firmware with scripting and Modbus TCP.
It has a built-in relay with dry contact (terminals I and O, max 2 A / 240 V) and stores at least 60 days of data at one-minute resolution. Its limit: 50 A per channel.
Choose it if: you want professional panel mounting and a wired network connection.
Shelly Pro 3EM: the reference three-phase meter
Three-phase DIN-rail meter with four CT clamp inputs (three phases plus neutral) and up to 120 A per phase. It is 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 is no space
It shares chassis and electronics with the Pro 3EM, but instead of three split-core clamps it uses the 3CT63: a single piece that integrates the three phases and mounts directly over the circuit breaker.
In exchange, two limitations: the current drops to 63 A and the conductor opening is 9 mm.
Looking for a professional model?
The four meters in the Pro range (EM-50, 3EM, 3EM-3CT63 and 3EM-400A) share DIN-rail format, connectivity and Modbus TCP, and deserve a comparison of their own. You will find it in the Shelly Pro range comparison, where we go into each one's maximum current, clamp type and the 400 A model for large installations.
The clamp defines the model
It is the practical difference most people overlook when buying. The clamps are not interchangeable between models: each meter is calibrated for its current transformer.
Frequently asked questions
EM Gen1 or EM Gen3?
For a new installation, 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 on a three-phase installation?
Only if you are content measuring one of the three phases. The EM, the EM Gen3 and the Pro EM-50 take their reference voltage from a single phase, so they cannot correctly calculate the power of the other two.
Can I fit a 120 A clamp on a Pro EM-50?
No. It is designed for 50 A transformers and its measurement range only goes that far.
Which ones speak Modbus?
The four meters in the Pro range: the Pro EM-50, the Pro 3EM, the Pro 3EM-3CT63 and the Pro 3EM-400A. It is Modbus TCP over port 502.
Which one do I need for solar self-consumption?
They all measure in 4 quadrants, meaning they distinguish import from export. For a single-phase home the EM Gen3 or the Pro EM-50 is enough; for three-phase, the Pro 3EM. We explain it in the guide on how to measure your solar self-consumption.
Which ones can cut the power or switch on a load?
The Shelly EM, the EM Gen3 and the Pro EM-50 have a built-in relay. The two three-phase meters need the Shelly Pro 3EM Switch Add-on. In every case the output drives a contactor: never connect the load directly.
Do they replace my utility meter?
No. They are monitoring meters, not certified billing equipment.
Quick summary
- Single-phase home, new installation → Shelly EM Gen3
- Single-phase with a very long history → Shelly EM
- Single-phase with a 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
- More than 120 A per phase → Shelly Pro 3EM-400A
Still unsure? Write to us with your panel details (phases, contracted power and available space) and we will tell you which one you need. Technical support in English and shipping from Spain.
Leave a comment