How to Choose an Energy Meter: 6 Essential Criteria

Complete guide to choosing an energy meter: single or three-phase, direct or CT, MID certification, Modbus, dual tariff. Socomec, Finder, Lettel ranges.LM

Lucas Moreau Electrical Engineer · Low-Voltage Installation Specialist · 15 Years of Experience

Key Takeaway

To choose an electrical energy meter, evaluate 6 criteria: network type (single-phase or three-phase), rated current (1 A to 100 A direct, or via CT for higher ratings), MID certification (mandatory for billing), communication protocol (Modbus RS485, M-Bus, pulse output), advanced features (dual tariff, reactive power measurement, THD), and mounting format (DIN rail modular, panel mount, door display). The MID directive 2014/32/EU guarantees measurement accuracy for legal billing purposes.

What is an electrical energy meter?

An electrical energy meter is a measuring instrument that records the amount of energy consumed or produced by an installation, expressed in kilowatt-hours (kWh). It enables real-time consumption monitoring, identification of energy-intensive loads, and energy billing.

Two main categories exist:

Sub-metering: installed downstream of the main utility meter, they measure consumption of specific zones, equipment, or tenants within an installation.
Billing meters: MID-certified, they are used to re-bill energy to third parties (tenants, condominiums, EV charging stations) with legal validity.

Key point An energy meter differs from a power analyzer. The meter primarily records cumulative energy (kWh). A power analyzer provides comprehensive real-time analysis: power, voltage, current, harmonics, power factor, etc.

6 selection criteria for an energy meter

1Network type: single-phase or three-phase

The meter must match the installation's network type:

Single-phase vs three-phase meters
Type	Network	Typical use
Single-phase	230 V, 1 phase + neutral	Residential, small commercial, individual circuits
Three-phase	400 V, 3 phases + neutral	Industrial, commercial, high-power installations

A single-phase meter measures one circuit. A three-phase meter simultaneously measures all three phases, calculates total and per-phase power, and detects phase imbalances.

2Rated current and connection type

Connection types by current rating
Type	Range	Principle	Use
Direct meter	1 A – 100 A	Current flows directly through the meter (built-in CTs)	Residential circuits, small commercial loads
CT-connected meter	> 100 A (via /1 A or /5 A CTs)	Meter reads secondary current from external current transformers	Main switchboards, industrial panels, high-power installations

Key point Direct meters are the simplest to install: just wire the phases directly. For ratings above 100 A, external current transformers (CTs) are required. The transformation ratio (e.g., 250/5 A) must be configured in the meter.

3MID certification: mandatory for billing

The European directive MID 2014/32/EU (Measuring Instruments Directive) governs measuring instruments used for energy billing. A MID-certified meter guarantees:

Certified measurement accuracy (Class B or C per IEC 62053).
CE + M marking attesting compliance.
Legal validity for re-billing energy to third parties.
Tamper-proof sealing preventing modification of measurement parameters.

⚠️ Legal requirement

If you use a meter to re-bill energy (tenants, condominiums, EV charging, sub-metered billing), MID certification is mandatory. A non-MID meter cannot serve as a legal basis for billing.

4Communication protocol

Energy meter communication protocols
Protocol	Type	Use
Modbus RTU (RS485)	Wired serial	Industrial standard, SCADA/BMS/EMS integration, up to 1,200 m
Modbus TCP/IP	Ethernet	IP network, remote monitoring, cloud integration
M-Bus	Wired serial	European metering standard, multi-meter remote reading
Pulse output (S0)	Dry contact	Simple interface, compatible with most PLCs and loggers
LoRa / NB-IoT	Wireless	Long-range remote reading, IoT, connected buildings

5Advanced features

Dual tariff (peak/off-peak): separate metering of peak and off-peak consumption for cost optimization.
Bidirectional metering: measures import + export, essential for photovoltaic self-consumption installations.
Reactive power (kVArh): reactive energy measurement for cos φ monitoring and compensation.
Harmonic analysis (THD): detection of harmonic pollution on the network.
Data logging: load curve storage for post-analysis.

6Mounting format

Modular (DIN rail): most common, installs in panels or enclosures. Width from 1 to 4 modules.
Panel mount: integrated into main switchboards and industrial distribution panels.
Door display: remote screen on the enclosure door for reading without opening.

Main brands and ranges

Energy meter brands — Ranges and features
Brand	Range	Features
Socomec	COUNTIS E	Complete single/three-phase range, direct or CT, MID, Modbus RS485
Finder	Series 7M / 7E	Compact modular meters, MID, Modbus, NFC
Lettel	MCT	High-current direct meters (up to 100 A), RS485

Discover our energy meters

→ All energy meters → Power analyzers → Current transformers (CTs)

Frequently asked questions — Energy meters

What is the difference between a single-phase and three-phase energy meter?

A single-phase meter measures consumption on a single circuit (230 V, 1 phase + neutral). A three-phase meter simultaneously measures all three phases (400 V, 3 phases + neutral), calculates total and per-phase power, and detects imbalances. The choice depends on your installation's network type.

What is a MID-certified meter and when is it required?

A MID meter is certified compliant with European directive 2014/32/EU on measuring instruments. It guarantees certified measurement accuracy and has legal validity for billing. MID certification is mandatory whenever the meter is used to re-bill energy to third parties (tenants, condominiums, EV charging stations). For internal consumption monitoring only, a non-MID meter is sufficient.

What is the difference between a direct meter and a CT-connected meter?

A direct meter measures current flowing directly through its terminals (built-in CTs), typically up to 100 A. It is simple to install. A CT-connected meter reads the secondary current from external current transformers mounted around power cables. It is necessary for ratings above 100 A and high-power installations (main switchboards, industrial systems).

What is a Modbus energy meter and what is it used for?

A Modbus energy meter communicates via the Modbus protocol (RS485 or TCP/IP) with a supervision system (SCADA, BMS, EMS). It transmits real-time consumption, voltage, current, power, and frequency data. This enables remote reading, energy optimization, anomaly detection, and integration into an energy management system (EMS) compliant with ISO 50001.

Can an energy meter be used for photovoltaic sub-metering?

Yes. A bidirectional meter measures both consumed energy (import) and produced energy exported to the grid (export). It is essential for monitoring photovoltaic self-consumption and calculating surplus sold. For surplus sales, the meter must be MID-certified.

What is dual tariff (peak/off-peak) on an energy meter?

Dual tariff allows separate metering of peak and off-peak consumption. This enables shifting energy-intensive usage (water heater, washing machine, EV charging) to off-peak hours when electricity is cheaper. The meter must receive a switching signal (dry contact, teleinfo) to toggle between the two tariffs.

Need help choosing the right energy meter?

Our technical team will help you select and size your metering solution.

Contact our technical team

By phone: +33 1 43 44 60 00 · By email: [email protected]

Key takeaways

Choose single-phase or three-phase according to your installation's network type.
Direct meters (up to 100 A) are simplest; for higher ratings, use external CTs.
MID certification is mandatory for any energy re-billing to third parties.
Modbus RS485 is the standard protocol for EMS or supervision integration.
Dual tariff (peak/off-peak) enables cost optimization by shifting consumption.
A bidirectional meter is essential for photovoltaic self-consumption monitoring.
Socomec (COUNTIS), Finder (7M/7E), and Lettel (MCT) cover most metering needs.