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Requirements of the calibration law


For all operators of public charging infrastructure, there are concrete requirements for charging and billing in accordance with the calibration law. This includes: accurate measurement, assignment of customer data and a transparent as well as a secure transfer of transaction data to a billing platform, the back-end. In order to meet the requirements of the customer protection law, the charging station manufacturers are increasingly relying on so-called public key signature procedures as a technical measure. Since April 2018, the Federal Network Agency has been working with the Federal Institute of Physics and Technology (PTB) and has provided an optional field for entering public keys on its website when registering charging stations. Public keys are numerical sequences displayed on measuring devices and are assigned to each charging point and thus give a direct reference to the location. The keys enable the user of charging points to check the correctness of the measured values by entering the number in a transparency software. The user also receives the complete load record with all important information.

Operators of loading equipment must provide a public key to the Federal Network Agency whenever the manufacturer has received a type-examination certificate with the corresponding obligation as a result of the conformity assessment in accordance with the Measuring and Calibration Act.

Another challenge is the topic of data security as well as the correct assignment of the data in case of a communication loss on the way to the billing platform. The current legal framework in the legal metrology MessEG and MessEV) therefore requires comprehensible transparency for publicly accessible charging infrastructure for the billing of a charging process.

A charging process includes the measurement and recording of the charged amount of energy as well as the time period of charging. The calibration law stipulates that customer data must always be uniquely assigned and that it must be transferred securely to a billing platform (OCPP 1.6 – Open Charge Point Protocol – capable back-end). 

As an active member of the association from the very beginning, the WALTHER-WERKE have significantly supported the development of an independent transparency software for a consumer-friendly market standard for measurement and auditing as part of the S.A.F.E. initiative (Software Alliance for E-Mobility). With this software, the customer can conveniently and safely read out and check all relevant data sets.

How it works



  1. The user authenticates them self via an app (using QR code) or with an RFID card.

  2. Prior to the start of the charging procedure, the measured values of the meter data are recorded by a calibrated measuring capsule in the charging device.

  3. The customer starts the charging procedure.

  4. At the end of the charging process, the charging procedure is terminated at the charging point or on the vehicle.

  5. Measured value acquisition of the meter data after completion of the charging procedure by a calibrated measuring capsule1 in the charging device.

  6. The independent charging station operator2 receives the signed measurement data sets of the charging procedure through a backend service provider3 (OCPP 1.6).

  7. The transferred data sets are stored in the backend until the legal retention period expires.

  8. The end customer can check their charging procedures using the S.A.F.E transparency software

LEGAL REGULATIONS: Conversion of non-compliant charging infrastructure

Since 1 April 2019, the Price Information Ordinance (PAngV) stipulates that all charging stations must have a suitable measuring system. However, the Federal Ministry of Economics, in cooperation with the charging infrastructure industry, has decided on a transitional regulation for the handling of charging stations that do not comply with the law. This decision prevented the possible decommissioning of charging stations after 31 March 2019. Thus, the operators also gain more time for retrofitting their charging systems in accordance with the law. At present, there is no formal deadline by which all DC and AC charging facilities have to be retrofitted throughout Germany.

The current procedure is as follows: each operator of loading equipment presents his specific, individual retrofit plan to the competent calibration authority. In this plan, the operator shall explain whether the manufacturer with whom he is cooperating is already involved in a conformity assessment procedure and, if this is the case, when it is likely that a type-examination certificate will be issued or when the market availability of a conformity-assessed loading device and the completion of the conversion of the complete stock of the loading point operator concerned is likely to be expected.

The following applies to the construction of new charging infrastructure: only conformity-assessed charging facilities may be built.

The WALTHER solution


As a future-proof and customer-friendly solution, WALTHER-WERKE offers its customers calibrated charging stations and wall charging stations by integrating a sealed measuring capsule consisting of a MID Modbus counter, a CryptoGateway and a new RFID display unit per charging point. With the measuring capsule, the measured values are determined in accordance with the law. WALTHER-WERKE has designed the measuring capsule in such a way that it can be installed in all new products and, depending on product range, construction and year of construction, can be retrofitted as far as possible in existing products. WALTHER-WERKE cooperates with the German-wide service partner Synfis in order to carry out a retrofit in accordance with the law.

Future-proof and customer-oriented

The CryptoGateway signs the customer loading process and encrypts it before sending it to the backend. The RFID display unit with LCD display visualizes all relevant data of the charging process to the customer and, at the same time, displays the difference value between the current meter reading and the meter reading at charging start. A measurement value that goes beyond the standard on the market.   
The measuring capsule has a local ring memory on which the load data is recorded.
The public key is also displayed as a QR code. For authentication, a new RFID reader for cards from MIFARE Classic and in the future for DESFire is integrated in the housing of the display according to the NFC standard.

Completely user-friendly and on an equal footing.