Shelly has six energy meters in its range and, side by side on a shelf, they all look as if they do the same job. Choosing the wrong one is still expensive: a clamp that does not fit round the cable, a single-phase meter on a three-phase supply, or a meter with no relay when a contactor needed driving.
All of them state 1% accuracy, so accuracy is not a criterion. Four things decide, in this order: the phases, the maximum current, whether you need a relay, and the type of clamp.
Single-phase
| EM | EM Gen3 | Pro EM-50 | |
|---|---|---|---|
| Channels | 2 | 2 | 2 |
| Max. current | 50 or 120 A | 50 A | 50 A |
| Relay | Yes | Yes | Yes (2 A) |
| Bluetooth | No | Yes | Yes |
| Ethernet | No | No | Yes |
| Scripting | No | Yes | Yes |
| Modbus TCP | No | No | Yes |
| DIN rail | With bracket | Yes | Yes |
Three-phase
| Pro 3EM | Pro 3EM-3CT63 | Pro 3EM-400A | |
|---|---|---|---|
| Channels | 3 + neutral | 3 + neutral | 3 |
| Max. current | 120 A | 63 A | 400 A |
| Clamp | 3 × 120 A CT | Combined 3CT63 | 3 × 400 A CT |
| Relay | No | No | No |
| Matter | Yes | No | No |
| History | 45 days | 60 days | 60 days |
The four in the Pro range — the Pro EM-50 and the three three-phase meters — share a 94 × 19 × 69 mm DIN-rail format, Wi-Fi, Ethernet and Bluetooth, four-quadrant metering and Modbus TCP. Within that range, connectivity sets nobody apart.
Choosing in three questions
- Single-phase or three-phase? A single-phase meter takes its voltage reference from one phase: on a three-phase supply it can measure that phase, not the other two.
- How many amps? This is the question that rules out the most models. For reference, 50 A single-phase is about 11 kW, and 63 A three-phase is around 43 kW of contracted power. Do not size to the limit: on a supply of exactly 63 A, the 120 A model leaves room to grow.
- Does it have to act on anything? If it must switch a load as well as measure, you need a relay — or, on the three-phase meters, an accessory.
Shelly EM: the veteran
Still a reasonable choice for a single-phase home: two channels, a relay for a contactor, and 365 days of history stored on the device, the longest in the range. What it lacks is everything since: Wi-Fi only, no Bluetooth or Ethernet, and as a first-generation device no scripting and no Modbus. On a DIN rail it needs a separate bracket.
It makes sense if you want more than a year of history held on the meter and need nothing else.
Shelly EM Gen3: the sensible single-phase choice
The same idea — single-phase, two channels, dry-contact relay — with current electronics. It adds Bluetooth, which makes commissioning much easier, scripting for automations that run on the device itself, and DIN-rail mounting out of the box; it is compact enough to fit a back box too. The one thing it gives up against the EM is memory: it keeps considerably less history.
For most new single-phase installations, this is the one.
Shelly Pro EM-50: single-phase for the panel
Two channels of up to 50 A, Ethernet, Bluetooth, scripting and Modbus TCP, in one DIN-rail module. It has a built-in dry-contact relay on terminals I and O, rated 2 A maximum at 240 V, and keeps at least 60 days at one-minute resolution. It is the only meter in the Pro range with a relay.
For a professional panel, a wired network, or measuring two circuits and acting on one with no extras.
Shelly Pro 3EM: the three-phase reference
Four clamp inputs — three phases and neutral — and up to 120 A per phase. The neutral clamp is optional and not included. It is the only Shelly meter that supports Matter, and it adds phase-sequence error detection, per-channel calibration and a minimum-load threshold.
Two details: phase C powers the device as well as being measured, and its history is the shortest in the Pro range, 45 days. The practical drawback is the clamps: three 120 A CTs take room, and they do not always fit in a panel that is already full.
Shelly Pro 3EM-3CT63: when there is no room
The Pro 3EM’s electronics with a different clamp: the 3CT63 is a single 14 × 54 × 26 mm piece that covers all three phases and sits directly on the circuit breaker. The price is two limits: 63 A per phase and a 9 mm cable opening. The second causes the most returns: it is the outside diameter of the cable with its insulation, not the cross-section in mm². Measure it before you buy.
Shelly Pro 3EM-400A: large installations
Raises the ceiling to 400 A per phase, for warehouses, distribution centres or solar plants of some size. It adds an optical pulse indicator for following consumption at a glance and keeps 60 days at one-minute resolution. If you stay under 120 A per phase, you do not need it.
The clamp belongs to the meter
This is the difference most people miss: clamps are not interchangeable between models. Each meter is calibrated for its own current transformer, and fitting another model’s clamp gives readings scaled by the wrong factor.
- Shelly EM: split-core clamp, 50 A or 120 A depending on the version.
- EM Gen3 and Pro EM-50: 50 A clamps, one per channel.
- Pro 3EM: three 120 A split-core clamps.
- Pro 3EM-3CT63: the combined piece, 63 A and 9 mm.
- Pro 3EM-400A: three 400 A clamps.
Frequently asked questions
Which ones can switch a load?
The EM, the EM Gen3 and the Pro EM-50 have a relay. The three three-phase meters need the Shelly Pro 3EM Switch Add-on. In every case the output drives a contactor coil: never connect the load directly.
Which ones speak Modbus?
The four in the Pro range, over Modbus TCP on port 502, alongside MQTT and RPC.
Can I use a three-phase meter on a single-phase supply?
The Pro 3EM and the Pro 3EM-3CT63 accept single-phase wiring, but with one phase the Pro EM-50 or the EM Gen3 usually works out better.
Which do I need for solar self-consumption?
They all measure in four quadrants, which means they tell import from export. On single-phase an EM Gen3 or a Pro EM-50 is enough; on three-phase, the Pro 3EM.
Do they replace the utility meter?
No. They are monitoring devices, not certified billing meters. Their accuracy is ample for optimising and automating, but it carries no weight with your supplier.
In short
- Single-phase, new installation → EM Gen3.
- Single-phase, more than a year of history on the device → EM.
- Single-phase in a panel, with Ethernet or Modbus → Pro EM-50.
- Three-phase up to 120 A → Pro 3EM.
- Three-phase up to 63 A with a full panel → Pro 3EM-3CT63.
- More than 120 A per phase → Pro 3EM-400A.