Billing and use of calibrated meters

The MessEV and MessEG stipulate that calibrated meters must be used for official billing purposes. In the EU, MID-certified meters are considered calibrated. MID certification can be recognised by the 'M' enclosed in a rectangle with the last two digits of the year of manufacture. The number of the certification authority can be found to the right of the rectangle.

The cFos Power Brain Wallboxes are supplied as standard with MID-certified, i.e. calibrated, meters and are optionally available with a viewing window. This also ensures that the meter is easy to read as required by calibration law. A photo of the meter is generally sufficient as proof of the meter reading. This form of meter reading and billing is suitable in all contexts in which the Charging Column Ordinance does not apply. From 13 April 2024, the Charging Points Ordinance will be replaced by an EU-wide regulation, the AFIR (Alternative Fuels Infrastructure Regulation). We therefore only refer to the AFIR in the following.

In which situations does the AFIR (was the charging station ordinance) apply and when does it not?

The AFIR applies to public charging points for spot (ad-hoc) charging. Spot charging means charging as at a petrol station, without prior registration with a provider. Public charging points are those that are operated on public or private land and that anyone can access without prior registration, such as charging points at motorway service stations or in supermarket car parks. If the charging points are located on a site that can only be accessed by authorised persons, the AFIR does not apply. Such areas include

  • Company car parks that can only be accessed by employees (*)
  • Garages of apartment blocks
  • Car parks on private property belonging to employees for parking company cars
  • Club and association car parks that may only be used by members
  • Public car parks that can only be used by Car-Sharing members (special regulation)
In particular, the AFIR does not apply when charging company cars at the employee's home! In the past, the charging point ordinance has probably been applied overzealously to company cars and company car parks. The testing of so-called "wallboxes that comply with calibration law" referred to the situation of charging as at a petrol station, where the customer only wants to pay for what has gone into the tank. In contrast, the employee with an electric company car would like to bill the employer for the entire operation of the charging infrastructure, i.e. including the standby power of the charging station and any other costs. However, this is not covered by the charging point regulation. With the AFIR, the EU is therefore creating clarity here.
(*) However, if a company offers a charging point in its car park that can be used by guests or strangers for selective charging for a fee, the AFIR applies.

Wallboxes that comply with calibration law are therefore only necessary within the scope of the AFIR!

Billing of charging processes of several persons at one EVSE

The cFos Charging Manager offers a transaction log for billing charging processes of different users at a wallbox, in which the user IDs and RFIDs or PINs of the users, including the charged kWh, are saved in the form of a CSV file. This can be analysed automatically and loaded into Excel, for example. In many situations, this should be sufficient to create useful invoices. Specific proof of the charging processes can be provided with meter photos if necessary, e.g. if the charging current is to be billed to the car park tenants once a year in a residential complex. If individual charging processes are to be recorded "forgery-proof", the cFos Charging Manager can either sign the charging processes itself or create files with the help of a signing meter, which can later be checked using verification software, see explanation below. Optionally, all charging processes can be forwarded to an OCPP billing backend. The signed meter readings of "calibration-compliant" wallboxes are then also forwarded accordingly. These signed meter readings then replace the handling of meter photos.

Transmitting signed meter readings to a billing backend

The cFos Charging Manager can use the Lovato DMED341MID7E signing meter and the EMH iML e-moc to record charging processes in compliance with calibration law and transmit them to a billing backend. This can then generate calibration-compliant invoices that can be verified using the S.A.F.E. programme. To do this, you must install the meter (available from us) in a small distributor housing near the wallbox and seal the housing and the Modbus cabling if necessary. In the cFos Charging Manager, attach the signing meter to the wallbox whose charging processes you want to sign. In addition, set the option "Save externally signed meter readings" for the wallbox. The cFos Charging Manager then proceeds as follows: Charging is deactivated until a car has been plugged in and charging has been authorised, e.g. using RFID. Before charging is activated, the Charging Manager generates a signed meter reading. The transaction continues until the car is unplugged. After unplugging and deactivating the wallbox, the cFos Charging Manager generates another signed meter reading. Both meter readings are then forwarded to an OCPP backend as a data stream that complies with calibration law and are also stored in the Charging Manager itself in a form that can be verified by S.A.F.E. so that you can download them under "Users" → "Charging processes" and present them to your employer or the tax office, for example.

This constellation allows the use of wallboxes that do not comply with calibration law, in particular the cFos Power Brain Wallbox. The legal-for-trade inspection of wallboxes actually only relates to public charging points. Among other things, it is checked that only the kWh charged into the car are recorded with the calibration law-compliant billing data. However, in many applications, e.g. when charging a company car at home, the operating costs of the wallbox are also billed and reimbursed. The employer only needs plausible data for the tax office, such as meter photos or signed meter readings, which can then be analysed automatically.

Saving and checking meter readings in compliance with calibration regulations

This function allows you to bill with the cFos Charging Manager in compliance with calibration law - without having to use an additional external OCPP backend.

Some "custody transfer compliant" wallboxes can save a signed meter reading before and after charging and transmit it via OCPP. If the cFos Charging Manager recognises such a meter snapshot in the OCPP data, it saves it in addition to the normal transaction log. It is signed by the wallbox with a private key. To check whether a meter snapshot is valid, you need the public key of the corresponding meter. The cFos Charging Manager can use the public key to verify the signature of the meter readings. Alternatively, you can also use the free S.A.F.E. software for verification. However, make sure that you read out and save the public key in a trustworthy environment. This is because if you always read it out with the current counter readings, an attacker (forger) can deliver his public key with his forged counter readings and the verification software can no longer recognise the forgery.

You can avoid this problem with the cFos Charging Manager by storing the public key for the meter in the wallbox settings of the Charging Manager. The cFos Charging Manager can also extract this automatically from the OCPP data, if available. However, to be on the safe side, you must obtain the public key from a trustworthy organisation or compare it with the key stored in the Charging Manager. The Federal Network Agency provides the public key for some meters, for some meters it is printed on the meter or you must contact the manufacturer of the wallbox or meter.
As soon as a public key is stored in the wallbox settings of the Charging Manager, the Charging Manager only saves meter snapshots with this stored key (which you trust). You can then download the appropriate XML file matching the transaction log entry and have it checked in a verification software. In addition, the cFos Charging Manager shows whether the signature of the meter snapshot could be validated with the public key: green lock symbol if validated, yellow if the signature could not be validated, no symbol if no signed data is available.
In the transaction log, you can download the counter snapshots for all transaction logs, for a specific wallbox or for a single transaction. In a business context, you can store this data (possibly together with external verification software) for six years and thus fulfil the legal requirements.
If you do not have a signing meter and all parties trust the cFos Charging Manager, you can also activate "Sign and save internal meter readings" in the wallbox settings. The cFos Charging Manager then signs the meter readings itself before and after a transaction - just as a "calibration law-compliant" wallbox would do. The Charging Manager generates a key pair if it does not already exist and then displays the public key so that you can use it for external verification software.