When measuring the electric energy charged in electric vehicles, the requirements of the Measuring Instruments Act must be considered if charging is invoiced based on the measured amount of energy. The requirements apply to the measuring instrument used in the measurement of electric energy, its display and the saving of measured data. The requirements of the Measuring Instruments Act apply to alternating current (AC) and direct current (DC) measuring instruments.
The manufacturer of a measuring instrument is responsible for its conformity with requirements. The party that uses measurement results for billing purposes is responsible for the conformity of measuring instruments with requirements during their use.
Separate requirements for AC and DC measuring instruments
The charging systems of electric vehicles use either DC or AC. Currently, these different types of electric energy measuring instruments are subject to separate requirements.
Requirements for AC measuring instruments
AC measuring instruments must meet the requirements of the Measuring Instruments Directive (MID). The measuring instrument must be furnished with the CE marking to indicate its conformity with requirements (Image 1).
Figure 1. A marking indicating conformity of measuring instruments with MID. In the example image, the measuring instrument’s year of manufacture is 2022.
An EU declaration of conformity must also be provided with a measuring instrument. The declaration of conformity of a measuring instrument conforming with MID must indicate the modules used in demonstrating conformity, the certificates granted (e.g. an EU type examination certificate and a certificate of production quality assurance), and the notified bodies that supervise them (the structure of the EU declaration of conformity is presented in MID Annex XIII).
Requirements for DC measuring instruments
Currently, no general requirements exist for DC measurements in the EU. However, a DC measuring instrument must carry a type approval. For example, a DC measuring instrument can carry a type approval based on the national requirements of an EU or EEA Member State (e.g. Germany), allowing its conformity with requirements to be verified in Finland using the mutual recognition procedure. A national type approval symbol may later have to be applied for a European approval in Finland.
An EN standard (prEN 50470-4) that addresses European MID requirements is under preparation. It is based on the IEC 62053-41:2021 standard.
The accuracy class of measuring instruments, and environmental conditions
The appropriate accuracy class of a measuring instrument is B. The measuring instrument’s operating temperature range must be suitable for the location in which it is used, taking temperatures below zero and the sun’s thermal radiation into account.
Public or private charging?
The charging of electric vehicles is divided into two categories (utility measurements and direct sales). The Measuring Instruments Act treats measurements differently, depending on whether measurements are public activities or utility measurements, in which the charging system measures the energy consumed by a single customer.
1. Charging station in a housing company
If the charging system for electric vehicles only measures the invoiced energy consumed by a single customer, e.g. an owner of a parking space, for charging an electric vehicle, this type of charging is within the scope of utility measurements as referred to in the Measuring Instruments Act.
Technically, it may be possible to also supply the charging energy from a dwelling unit’s electrical energy meter without measuring the charging energy separately in the parking space.
When using an AC charger, the electrical energy meter must meet the requirements of MID before its commissioning.
No verification laid down in the Measuring Instruments Act is required during commissioning.
As the question is of utility measurements, no regular in-service verification is required during use.
2. Public or semi-public charging station
In the Measuring Instruments Act, charging an electric vehicle at a public charging station is a trading transaction – direct sales of electric energy and its billing in accordance with measurements.
AC charging station, or slow public charger:
When using an AC charger, the measuring instrument at the public charging station must meet the requirements of MID.
No verification laid down in the Measuring Instruments Act is required during commissioning.
According to the Measuring Instruments Act, a measuring instrument must be type approved.
According to the Measuring Instruments Act, a verification is required during commissioning if the measuring instrument is not within the scope of application of MID. In practice, the need to verify a DC charging station depends on the measuring instrument’s properties and approval. See the description of the mutual recognition procedure below.
Regular verifications must be carried out every three years.
Measuring the charging of company cars
The Finnish Tax Administration requires the amount of electricity charged at home and invoiced from the employer to be verified reliably using a separate measuring instrument. The amount of electricity charged in a company car and invoiced from the employer can be reliably verified using a separate sealed measuring instrument conforming with MID.
Meter display
An electrical vehicle supply equipment (EVSE) in which the charged electrical energy is measured for billing purposes must have a display that is easily visible to consumers. The displayed reading is the measurement result, based on which the price to be paid is determined. When an EVSE includes a meter display, no (MID-)certified data transfer connection and background system are required. In a measuring instrument used by a single user, the meter display can also be behind a locked cover, provided that the user has a key to it.
The meter display must show a cumulative energy reading and/or the amount of energy consumed during a charging event. In public charging, it is recommended that the amount of energy consumed during a charging event be shown. In public charging, any figures higher than 100 kWh can be hidden in the cumulative reading.
Energy measurements and cable losses
There can be no losses between the meter and charging connection that have an impact higher than one sixth of the maximum permissible error on measuring results (NordCharge recommendation). If required, cable losses can be compensated by parameter settings in a sealed meter or by using a 4-wire measurement.
Recording measurement results and presence via a remote connection
If a party to a transaction gives permission for charging through a remote connection, it is interpreted that the other party to the transaction is present in the transaction. As a result, the measuring instrument does not need to record the measurement results (i.e. no log memory) or unique transaction information. In other words, the MID requirement for the permanent recording of identification information does not apply (MID Annex I, 11.1).
The charging permission given through a remote connection means for example the identification of an RFID card held by the user as part of an agreement with the charging operator and the permission to start the charging transaction based on this agreement. As the other party to the transaction has approved the transaction, it can also suspend the transaction through a data connection, if required.
Permanent proof of measurement results
After charging, permanent proof of measurement results and the transaction’s identification information must be presented at request. After the charging transaction, it must be possible to compare the information provided with the charging station’s meter display.
Permanent proof of measurement results and the transaction’s identification information includes a paper printout (i.e. receipt), text message, email or data saved by the charging application (MID Annex I, 11.2).
Individual charging transactions can be presented itemised in a consolidated invoice for the invoicing period. When a charger includes a display, no certified data transfer connection and background system are required.
