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Metrology in the regulation of electric vehicle charging stations

This article summarises the current situation and the actions being carried out by the Spanish Metrology Centre (CEM) in the area of legal metrology in relation to electric vehicle charging stations. Authors: Javier Diaz de Aguilar(1) , Marisa Luisa Romero(1) , Laura Matias (1), Yolanda Álvarez(1), Manuel Cervantes (1), Rodrigo Morales, Albert Pueyo, María Teresa Lopez (1).  (1)Centro Español de Metrología Fotos: (1) Centro Español de Metrología (CEM)


The viability of electric mobility requires an adequate infrastructure of charging stations for both urban and interurban mobility, the latter being more complex due to the limited autonomy of electric vehicles (maximum energy stored in the batteries) and the time needed to complete recharging. On the other hand, the correct measurement of the energy transfer that takes place between the charging station and the electric vehicle (EV) requires legal control to ensure consumer confidence and protection. This article summarises the current situation and the actions being carried out by CEM in the area of legal metrology: establishment of national regulations (there are currently no European regulations), and its participation in European (WELMEC, EURAMET) and international (OIML) committees and in the area of metrological infrastructure for the characterisation of charging stations.

The development of the regulation requires the support of an adequate metrological infrastructure on the one hand to avoid the elaboration of requirements without practical application. Source: Centro Español de Metrología (CEM)

The use of electric vehicles (EVs) requires an adequate infrastructure of charging stations for both urban and interurban mobility, the latter being more complex due to the limited autonomy of electric vehicles (energy stored in the batteries) and the time needed to complete the charge (available charging power).


On the other hand, the correct measurement of the energy transfer that takes place between the charging station and the electric vehicle requires legal metrological control ("control of the measurement tasks envisaged for the scope of application of a measuring instrument, for reasons of public interest, public health, public order, protection of the environment, levying of taxes and charges, consumer protection and fair trading [1,2]). This energy transfer is similar to electricity meters in the sense that they measure the energy transferred but have several differential aspects: the energy is supplied and measured to different users, except in the case of domestic chargers, it is rather direct sale, it can be supplied in direct current and at different charging powers, the charging stations are outdoors, the load is usually of unity power factor, the instrument performing the measurement can be integrated inside the station, etc. Perhaps in terms of public supply they are more similar to automotive fuel dispensers, hence the name "petrol stations". However, charging stations are being configured in such a way that there are different payment methods, in addition to the so-called ad-hoc price, which is established when there is no previous contract; furthermore, the trend in the designs is that there is no user information screen and that the registration of the transaction is done by telematic means.


Regardless of the approach, there is a clear need for specific regulation and a metrological infrastructure for its implementation.


This article reviews existing regulation at national, European and international level and describes the actions being taken by the EMC to establish national regulation, pending European regulation. The national legislation that is being drafted as a new specific annex to Order ICT/155/2020 of 7 February [3] will ensure consumer protection in energy transactions at charging stations, respecting the principle of proportionality, without requiring anything that is not strictly necessary, and ensuring that the regulation does not hinder the development of charging station infrastructure.


It also describes the actions it is carrying out at international level by participating in the WELMEC, EURAMET and OIML working groups.


Last but not least, any legal metrology regulation requires a metrological infrastructure to support it. Currently, there are no laboratories in Europe with the capacity to perform conformity assessment of charging stations. In this sense, the EMC has developed a new laboratory for the evaluation of charging stations.


Regulatory actions in Spain

At present, there is no specific legislation at European level to regulate such a transfer and it is only regulated to a limited extent in some European countries. The first question is whether the European directive on measuring instruments known as MID includes charging stations, in which case national regulations are not necessary and it would be sufficient to establish harmonised application standards. On the other hand, charging stations can operate in direct current and the MID was not drafted with the measurement of electrical energy in direct current in mind. The question then arises as to whether it is necessary to amend the MID to cover DC meters and charging stations; in the case of charging stations it would affect the meter built into the station; a different situation would be if this function were integrated into the electronics of the station. At the time of writing this article, the European Commission is evaluating the possibility of modifying the MID, among other aspects, fundamentally to include charging stations.


In Spain, the regulation is contained in the Complementary Technical Instruction (ITC) BT-52, "Installations for special purposes. Infrastructure for charging electric vehicles" [4], of the Low Voltage Electrotechnical Regulation, which specifies the need to have a secondary energy meter for the repercussion of costs; this meter must comply with the applicable legal metrology regulations.


Since both European and national regulations are not sufficient, especially when considering DC charging stations and high power charging stations, CEM initiated a new line of work to develop the corresponding legal metrology and at the same time ensure the metrological support for its application. In this sense, among other actions, it is worth highlighting the constitution of a national working group convening the interested parties with which regular meetings are held, the participation in the specific committees first of OIML and later also of WELMEC; finally, within EURAMET, the "Legal EV charge" project was created to provide metrological support to the corresponding regulation. In recent months, the EMC has actively participated in the working groups to respond to the European Commission on how to modify the MID to include these instruments.



Within the electricity subgroup of WELMEC, body for cooperation in legal metrology in Western Europe, group 11, the initially so-called ad hoc group (ahg 3) was set up as an information exchange point and included among its tasks the development of guidelines for electric vehicle charging with the following objectives:


- To develop a joint view on whether MID is applicable to the delivery of electrical energy for electric vehicle charging pending the development of a harmonised standard.

- To give a joint approach to the need to amend the MID to include the measurement of DC power.

- Assess the differences between the different members with regard to national regulations on charging stations. Prepare help tables for manufacturers.

- List the different requirements in each state for charging stations in use to facilitate the work of charging station operators.

- Provide testing guidelines for charging stations in a way that is consistent with legal metrology requirements.



The activities within EURAMET (European Association of National Metrology Institutes) in reference to charging stations started with the preparation of a project, within the standardisation call, to investigate the specific requirements for charging stations. This project was approved, but was not funded in the end. However, in order to carry out common research work on charging stations, the EURAMET project "LegalEVcharge (EURAMET TCEM project no 1539)" was set up to prepare the technical infrastructure to support legal metrology, including laboratory and on-site testing, and to serve as a forum for exchange of views with the various stakeholders.


Finally, in 2023, within the call of the European Partnership on Metrology [5], a project for the development of European metrology for charging stations has been approved under the industry theme.



The OIML (International Organisation of Legal Metrology) technical committee TC12 included an annex for charging stations as part of the work on the revision of the recommendation for electricity meters R46 [5]. During the elaboration of this annex it became clear that due to the above mentioned peculiarities not all requirements for electricity meters are applicable to charging stations and some requirements are only applicable to charging stations. In this regard, it was decided to request the approval of a new project exclusively for charging stations. Considering the urgent need for a common regulatory framework, to avoid that each country adopts different requirements, and the necessary time required for the approval of an OIML recommendation, the working group decided to start the work by drafting a guide (there is no moral obligation for member countries to implement it but it can be used as a reference) and then proceed with the drafting of the recommendation. The guide was finalised and published on the OIML website [6] and on the basis of this guide the corresponding regulation is being prepared.


During the development of the guide, the EMC held meetings with the working group involving the actors involved. The suggestions of the working group were forwarded to the coordinator of the development of the guide and many of the comments have been incorporated.


New charging station laboratory

Due to the specific characteristics of charging stations, there is no adequate metrological infrastructure for conformity assessment in Europe. Most European countries are in the process of developing new measurement capabilities to cover the required measurement range. Among the peculiarities of these instruments is the ability to measure high electrical power over 300 kW in direct current.


The charging stations will be outdoors and in very variable environmental conditions, ranging from high temperatures, in some cases above 40 ºC to temperatures well below 0 ºC. In addition, solar irradiation, rain, possible accidental shocks, etc. have to be considered. All of these can affect the accuracy of the measurement and it must be ensured that the requirements are maintained under these conditions. On the other hand, the charging power, the amount of energy transferred from the station to the electric vehicle, can be very variable depending on the vehicle, the state of charge of the batteries, the condition of the batteries, etc., which makes it necessary to verify compliance with the energy measurement requirements in all conditions.



One of the key elements in meeting the EU's climate targets is electromobility; currently the most limiting factor in its development is the availability of an adequate infrastructure of charging stations. The sale of electric vehicles is limited by the unavailability of adequate charging station infrastructure. The development of charging station infrastructure is conditional on the existence of a sufficient number of electric vehicles to ensure their profitability. Regardless of the above, regulation is needed to ensure consumer protection while maintaining the principle of proportionality, i.e. not stipulating unnecessary requirements that hinder the development of charging stations. On the other hand, OEMs should be aware of the regulation in advance in order to optimally design their products and avoid costly modifications at a later stage. The current global market also makes it necessary for the regulation to be common to all countries or at least in the European market. Finally, the development of the regulation requires the support of an adequate metrological infrastructure on the one hand to avoid the elaboration of requirements without practical application and on the other hand to be able to verify compliance with these requirements.


In view of the above, more than two years ago the CEM started its activity with regard to charging stations, covering the above aspects, as well as having a national regulation harmonised with common European and international requirements and providing a metrological infrastructure to support the development and application of the regulation. Stakeholders (manufacturers of electric vehicles and charging stations, charging station operators, users, test centres, electricity distributors, etc.) have contributed to the project.



[1]  Real Decreto 244/2016, de 3 de junio, por el que se desarrolla la Ley 32/2014, de 22 de diciembre, de Metrología./ Royal Decree 244/2016, of 3 June, implementing Law 32/2014, of 22 December, on Metrology.


[2] Directiva 2014/32/UE del parlamento europeo y del consejo de 26 de febrero de 2014 sobre la armonización de las legislaciones de los Estados miembros en materia de comercialización de instrumentos de medida (refundición)./ [2] Directive 2014/32/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the placing on the market of measuring instruments (recast).


[3] Orden ICT/155/2020, de 7 de febrero, por la que se regula el control metrológico del Estado de determinados instrumentos de medida./ [3] Order ICT/155/2020, of 7 February, regulating the State metrological control of certain measuring instruments.


[4] Real Decreto 1053/2014, de 12 de diciembre, por el que se aprueba una nueva Instrucción Técnica Complementaria (ITC) BT 52 “Instalaciones con fines especiales. Infraestructura para la recarga de vehículos eléctricos”, del Reglamento electrotécnico para baja tensión/[4] Royal Decree 1053/2014, of 12 December, approving a new Complementary Technical Instruction (ITC) BT 52 "Special purpose installations. Infrastructure for recharging electric vehicles", of the Low Voltage Electrotechnical Regulation



[6] OIML G-22 Electric Vehicle Supply Equipment (EVSE):




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