Sub-meters and portable electricity meters

A sub-meter measures the consumption of one part of a property behind the grid operator's main meter – such as the garage, a granny flat, a wallbox or a parking pitch. Portable versions with a Schuko or CEE connection are simply plugged in between and are suitable for campsites, events, building sites or the workshop. DIN-rail meters, by contrast, are permanently installed in the distribution board.

The difference from a plug-in energy meter lies mainly in the measuring technology and approval: sub-meters are built for continuous operation and higher currents and are often conformity-assessed under the European Measuring Instruments Directive (MID).

As soon as you bill third parties for electricity based on the readings, German measurement and calibration law (Mess- und Eichrecht) applies. The meter must then be approved for this purpose or MID-compliant, and the calibration period must be observed. Uncalibrated or "refurbished, reset" meters are fine for private monitoring but not suitable for legally sound billing.

Choose the connection to suit the application: Schuko for 230 V appliances up to 16 A, CEE 16 A or 32 A for three-phase power and campsites. Check the protection rating for outdoor use (IP44 or higher), the cable length and whether a daily counter can be reset without losing the total reading.

With electronic meters, an easy-to-read display is important; mechanical meters need no auxiliary power but are larger. With used offers, check the condition and calibration status.

Portable meters are flexible and quickly moved, but only suitable for plug-in appliances. If you want to record an area such as the garage, a wallbox or a granny flat permanently, a fixed DIN-rail meter is the cleaner solution. Get advice from a qualified electrician, who will also check the space in the distribution board and the circuit protection.