Splitting the electricity between tenants, separating a shop’s consumption from the flat above it, justifying a building’s shared costs: it is nearly always done by eye, with estimates that end in an argument. With a two-channel meter it stops being an estimate.
One device, two consumptions
The Shelly Pro EM-50 has two clamp inputs, IA and IB, of up to 50 A each. Each clamp goes round a different circuit and the meter records them separately, to 1% accuracy.
The uses that come up most:
- A home let by the room, or split in two. Each part on its own channel.
- A shop below a flat. The business’s consumption kept apart from the household’s, which also helps justify expenses.
- One particular load. The pool pump, an oven, the air conditioning: knowing what it really costs to run.
- Shared costs. A lift, a car park or communal lighting, measured instead of shared out by a coefficient.
Why the data holds up in an argument
Measuring is not enough; how it is kept matters. The Pro EM-50 stores at least 60 days at one-minute resolution in non-volatile memory, and exports it to CSV and JSON. You can pull the exact consumption for a period and attach it to a statement.
It also has a real-time clock, so the timestamps stay correct even if the internet goes down for days.
It is not a certified meter. It serves to share internal costs fairly and with evidence, but it has no legal standing with your supplier.
From data to action
What sets it apart from the three-phase meters is that it has a relay: it does not just watch. With scripts on the device it can cut a load past a threshold, switch a circuit on during off-peak hours, or send a warning when someone goes over the agreed consumption.
The output is terminals I and O, an isolated dry contact rated 2 A maximum at 240 V.
Those 2 A are for a contactor coil, never for the load. A water heater, a pump or an oven needs an intermediate contactor sized for its power. Wiring them directly destroys the relay, and it is the most expensive mistake made with this model.
What you need
- A Shelly Pro EM-50 and one free module on the DIN rail.
- Two 50 A clamps, one per circuit.
- If it is going to cut loads, a contactor sized for the real power.
Is it the right one?
The Pro EM-50 is single-phase and goes to 50 A per channel. On a three-phase supply, or a larger one, the Pro 3EM is the meter for the job.