MID (Measuring Instruments Directive) is an EU regulatory framework that sets requirements for the accuracy, conformity assessment, and marking of certain measuring instruments, including electricity meters. In EV charging, MID-compliant metering is used when the measured energy (kWh) is used for billing or other legally relevant transactions, helping ensure transparent and trustworthy charging costs for end users.
What Is MID?
MID refers to the EU Measuring Instruments Directive that defines:
– Which instrument types are covered (including electricity meters)
– Essential requirements for measurement accuracy and reliability
– Conformity assessment procedures and notified body involvement
– Marking and documentation requirements (e.g., CE + metrology marking)
An electricity meter that meets MID requirements is commonly called an MID meter, though the legal requirement depends on the country and the use case.
Why MID Matters in EV Charging
When a driver is billed per kWh delivered, the energy measurement can be considered legally relevant. MID-compliant metering helps:
– Provide fair, accurate billing and reduce disputes
– Support consumer protection and tariff transparency
– Improve trust in public and semi-public charging
– Enable compliance in markets where MID metering is required for public charging billing
– Support auditing and reporting for operators and site owners
For CPOs, MID metering can be a key requirement in tenders and public-sector projects.
Where MID Is Applied in Charging
MID metering can be implemented:
– Inside the EV charger (integrated MID-certified meter)
– In a separate meter cabinet measuring a feeder or group of chargers (less granular)
– In sub-metering setups for cost allocation (workplace, tenants, fleets)
For user billing per session, an integrated meter per charger/connector is often preferred because it ties energy directly to the individual transaction.
MID Metering vs “Standard” Metering
MID metering (legal-for-trade context)
– Conformity assessed to meet regulatory metrology requirements
– Marked and documented according to MID rules
– Designed for billing and legal measurement transparency
Standard metering (operational monitoring)
– Used for energy management and analytics
– May be accurate, but not necessarily certified for legal billing
– Often sufficient for internal reporting but not always for consumer billing
What to Look For in MID Compliance
– MID markings on the meter (CE + metrology marking)
– Documentation showing conformity assessment and accuracy class
– Sealing/tamper features where required
– Calibration and verification requirements (country-specific implementation)
– Clear traceability of meter ID to charger, connector, and billing records
Practical Considerations for EV Charging Projects
– Confirm local requirements: some countries require MID for public billing per kWh, others allow alternative approaches
– Ensure the CPMS uses the correct meter registers for billing
– Maintain consistent tariff communication (€/kWh, session fees, idle fees) to reduce disputes
– Plan maintenance access and replacement procedures without breaking compliance seals
– Use robust data integrity and logging to match metering values with charging session records
Related Glossary Terms
MID metering
Energy meter
Meter cabinets
Tariff structure
Fiscal metering
Charging session reporting
CPO (Charge Point Operator)
CPMS
kWh delivered per charger
Charging revenue