About ME, MID, and uncalibrated charging stations

Calibrating a wallbox: here’s what German measurement and calibration standards mean

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  • Charging
  • Technical
  • Billing
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You often see public charging stations in the German-speaking world reading the letters ME. They stand for "Mess- und Eichrecht" (measurement and calibration act). But what does that mean? What other calibration standards are out there? And why do I need a calibrated wallbox for my personal use? Here are the answers.
An energy meter counts the electricity flowing through it.

What is a calibrated wallbox?

Basically, “calibration” here means the mandatory examination of a measuring instrument to see if it complies with the underlying regulations specific to calibration law, especially calibration error limits. Not every wallbox is a measuring instrument as such; it is only one if it can also measure the energy flowing through it via an integrated energy or power meter. Whether and how a wallbox must be calibrated depends on the use of the meter result. If you only want to keep track your own use, you can do so with a charging station with an uncalibrated meter. But if you want to pass on energy costs, your wallbox must be calibrated. There are currently two calibration standards, whose validity depends on your location.

The EU standard: Measuring Instruments Directive (MID)

The Measuring Instruments Directive (MID) is an EU guideline specifying the requirements of measuring instruments. With the introduction of the MID, calibration in state-approved testing centres has been replaced by the manufacturer’s declaration of conformity. The calibration’s validity period continues to be based on national regulations. Only MID-certified energy meters (and thus MID-compliant wallboxes) may be used for billing energy costs. This is true for all of Europe – with the exception of Germany, where stricter requirements must be met.

The German standard: measurement and calibration act (Mess- und Eichrecht, ME)

The so-called measurement and calibration act (Mess- und Eichrecht, ME) is the German implementation of the European directive for the calibration of measuring devices (MID). Unlike wallboxes with uncalibrated or MID-certified meters, ME-compliant devices must store information about individual charging sessions in the charging station itself and over a longer period of time. As this requires more complex hardware, ME wallboxes tend to be a bit more expensive than MID-certified ones.

Who needs a calibrated wallbox?

To be able to lawfully pass on the costs for energy charged on a kWh basis, a calibrated meter must record the electricity used. This is true for hotels that want bill their guests for their charged energy as well as for parking garage operators. But also private citizens need a calibrated record of used energy: if tenants want to use a wallbox that is not connected to their own energy meter or if the company vehicle is regularly charged at home. The employer only accepts the energy costs incurred in this scenario if a properly calibrated wallbox is used.

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