A home’s electricity use is measured with three kinds of device: metering plugs for specific appliances, relays with power metering for each circuit, and clamp meters in the consumer unit for the total, single or three-phase. With solar panels, the consumer-unit meter separates what is consumed, produced and exported to the grid.
Three levels of metering
| Level | Device | What you learn |
|---|---|---|
| Appliance | Metering plug (e.g. Shelly Plug) | What the fridge, TV on standby or heater uses. |
| Circuit | Relay with metering (PM models) | Use of one circuit, water heater or pool pump, and control of it. |
| Home | Consumer-unit meter (Shelly EM or Pro 3EM) | Total use, live power and, with panels, the surplus. |
What you can do with the data
- Spot hidden consumption: standby appliances, a badly scheduled water heater or a pump that never stops.
- See when you use most and shift loads to cheaper hours.
- Check whether your contracted power is right.
- With solar panels, run the water heater, heat pump or car charger when there is surplus.
- Avoid tripping the power limiter by switching off a non-priority appliance near the contracted power.
Single-phase or three-phase
Most flats have a single-phase supply, so a one or two-channel meter is enough: one for total use and another, for instance, for solar production. Large homes, villas and warehouses with three-phase supply need a three-phase meter measuring each phase separately.
Clamps are chosen for the installation’s maximum current. Fitting in the consumer unit must be done by a professional with the power off.
Accuracy and limits
These meters are very useful for understanding and managing consumption, but they do not replace the utility meter, which is used for billing. Small differences between the two are normal.