Key Takeaway: The electric sub-meter measures the consumption of a specific circuit, allowing you to target energy savings and fairly allocate costs. This tool, available from 20€, is useful both in shared housing and in businesses, and contributes to reducing the carbon footprint. Its installation by a professional ensures safety and legal compliance.
Are you having trouble identifying the energy-consuming appliances in your home? The electric sub-meter precisely measures electricity usage by zone or device, such as a heating circuit or a floor. This device enables you to save up to 20% on your bill, fairly distribute costs among roommates, or establish justified charges in furnished rentals. Discover models (single-phase, three-phase, connected), selection criteria, installation by a certified CONSUEL professional, and the benefits of controlled consumption to reduce costs and carbon footprint within the legal framework (mandatory MID certification).
- What is an electric sub-meter and what is it used for?
- In what cases should a subdivision meter be used?
- How to choose the right electric sub-meter?
- Installing the sub-meter: a supervised and secure operation
- Legal framework: what you need to know about certification and re-invoicing
- Concrete benefits of sub-metering for your budget and the planet
What is an electric sub-meter and what is it used for?
An electric sub-meter, also called a division meter or electrical deduction meter, is an accessory device to the main meter. It measures electricity consumption in kWh for a specific area of a home or installation, such as a floor, a utility room, or a dedicated circuit (heating, lighting).
Its use allows distinguishing consumption of certain appliances or spaces. This helps to identify sources of overconsumption and adapt habits to achieve energy savings. For example, it reveals whether electric heating or standby devices account for a significant part of expenses.
It also serves to fairly divide electricity costs in shared housing or a condominium. In rental situations, it reports on consumption related to the rented area, although direct re-invoicing is strictly regulated by law. For professionals, it supports energy management compliant with standards like ISO 50001.
Two main types exist: the single-phase (up to 63A, MID certified) for standard homes and apartments, and the three-phase for industrial or high-energy installations. Although the Linky meter includes a similar function, a dedicated sub-meter offers more precise measurement for specific circuits.
In what cases should a subdivision meter be used?
For precise monitoring of domestic consumption
A sub-meter isolates the consumption of energy-intensive devices like heat pumps or charging stations. This allows adjusting their use according to variable rates (off-peak/on-peak hours) and optimizing costs. For instance, a heat pump could represent a large part of winter bills: a dedicated meter limits its operation to low-cost hours.
It also monitors usage in a utility room or home office. For professionals, this distinguishes business consumption, justifying tax deductions. Detailed readings demonstrate the dissociation between domestic use and professional activity.
For fair sharing of charges
In shared housing, the sub-meter divides bills according to actual consumption, avoiding flat-rate sharing. It is also applicable in homes divided into separate zones (ground floor/upper floor), with a meter per area for transparent billing, even with very different usages (e.g., occupied 24/7 vs occasional use).
For rental or professional use
In furnished rentals, it provides an objective basis for setting justified flat charges, respecting the law prohibiting direct re-invoicing (except for seasonal rentals). In businesses, it supports energy efficiency initiatives (ISO 50001 standard) by measuring consumption per zone or equipment. A business can thus identify high-consumption items, facilitating targeted adjustments.
- Monitoring the consumption of an energy-intensive device (heating, heat pump).
- Sharing electricity costs in a shared housing.
- Assessing the consumption of a rented zone (studio, utility room).
- Identifying the consumption of a workshop or home office.
- Facilitating a energy efficiency strategy.
How to choose the right electric sub-meter?
Choosing an electric sub-meter depends on your installation and needs. Modern models offer advanced features for optimizing energy management. Here are the essential criteria to consider.
Single-phase or three-phase sub-meter: what’s the difference?
The single-phase sub-meter is suitable for typical domestic installations. It measures consumption on a 230V network with currents up to 63A. This type is appropriate for a standard house, an apartment, or circuits such as lighting or electric heating.
The three-phase sub-meter is for high-power installations. It operates on a 400V network with currents exceeding 80A. It is essential for equipment like heat pumps, industrial ovens, or when the distance between the main meter and devices is significant. Note that this type requires a three-phase main meter.
Advanced features of modern sub-meters
Connected sub-meters incorporate technologies such as Wi-Fi or Modbus protocol (RS485). These options enable real-time monitoring via a smartphone app, like Tuya or Smart Life. Some models include an internal relay to control a circuit remotely.
Here is a comparison table of sub-meter types:
| Feature | Single-phase sub-meter | Three-phase sub-meter | Connected (Smart) sub-meter |
|---|---|---|---|
| Main use | Standard domestic installations | High-power, professional installations | Optimized monitoring, home automation, all installation types |
| Max. current | Typically 32A – 63A | Typically 80A or more | Variable (available in single- and three-phase) |
| Key features | Simple kWh measurement | Phase or total measurement | Real-time monitoring, remote control, dual tariff, history |
| Price range (device) | 20€ – 80€ | 50€ – 150€ | 40€ – 300€ |
Sub-meters equipped with dual tariffs (peak/off-peak) facilitate cost-effective management of consumption. Brands like Legrand, Schneider Electric, or Delta Dore offer MID-certified models, essential for legal billing in professional settings.
Installing the sub-meter: a supervised and secure operation
Why hire a qualified electrician?
Installing a sub-meter involves significant electrical risks: short circuits, fires, or electrocution. The NF C 15-100 standard requires a rigorous installation to guarantee safety. For new or renovated installations, a CONSUEL certificate is mandatory. Only professionals can ensure these requirements are met, avoiding unforeseen costs.
Major steps in installation
The installation follows a strict protocol, performed by a certified electrician:
- Cut off the main power via the main circuit breaker.
- Mount the sub-meter on the DIN rail in the distribution board, upstream of the circuits to be measured, verifying network compatibility.
- Connect phase and neutral wires according to the manufacturer’s diagram, respecting breaker sizes.
- Verify operation after restoring power: test measurement thresholds (kWh, voltage).
What is the cost of a sub-meter and its installation?
The device costs between €25 and €300 depending on features (single-phase, three-phase, MID certified). MID-certified models are at the higher end. Installation by a professional costs between €100 and €200, including labor and ten-year warranty. For a complete setup, the budget ranges from €150 to €300. These prices include compliance with standards, preventing unexpected expenses. Prices may vary depending on complexity (e.g., connected meter).
Legal framework: what you need to know about certification and re-invoicing
The importance of MID certification
The MID (Measuring Instruments Directive) certification is an essential European requirement ensuring the accuracy of energy meters used for commercial transactions. It is mandatory if the data from the sub-meter are used for billing.
A MID-certified sub-meter bears CE markings, “M,” and the manufacturing year, along with the certifying body’s code (e.g., “CE M08 1259”). This standard imposes strict tolerances (classes B or C) to prevent measurement errors.
Non-compliance means a non-certified sub-meter cannot be used for billing. It remains useful for energy monitoring without financial implications.
Electricity re-invoicing: permitted or prohibited?
Law strictly prohibits reselling electricity at a higher price than the purchase cost to a tenant. This applies even with a sub-meter, as reselling is reserved for authorized suppliers.
In long-term rentals, a landlord cannot issue an invoice based on the sub-meter. However, for furnished or seasonal leases, consumption can justify a flat fee included in charges, without annual reconciliation.
In rental agreements, these provisions are as important as clauses in your home insurance.
Non-MID certified sub-meters are authorized for consumption analysis but not for precise billing. In case of doubt, consult an electrician or legal expert to avoid legal sanctions.
Concrete benefits of sub-metering for your budget and the planet
The electric sub-meter measures the consumption of a specific circuit or dwelling. This detailed monitoring helps identify energy-intensive posts and achieve savings of up to 30%, especially by isolating heating, air conditioning, or standby device consumption. The data supports adapting habits or replacing inefficient equipment.
By distributing costs according to actual usage, this device prevents conflicts among roommates or tenants. For example, a sub-meter on a rented studio allows billing only the occupant, ensuring fair management of charges. This encourages responsible consumption through transparent data, motivating everyone to reduce their impact.
- Precise management of your energy budget.
- Fair and transparent cost distribution among multiple occupants.
- Quick identification of most energy-consuming devices to optimize.
- A step towards more responsible and ecological consumption.
Saving on your bills is an excellent first step toward better managing your budget and savings daily. This approach also reduces the carbon footprint associated with energy production, consistent with ISO 50001 principles. By combining the sub-meter with tools like energy management systems, it becomes possible to monitor consumption in real time, adjust habits, and plan savings, thus enhancing both financial and ecological impacts.
The electric sub-meter allows precise control over consumption by isolating high-energy-use posts, distributing costs fairly in shared housing, and optimizing bills. As an energy management tool, it offers both financial savings and an ecological approach by reducing waste, while facilitating responsible and informed electricity use daily.
FAQ
Is it legal to install an electric sub-meter?
It is perfectly legal to install an electric sub-meter, provided that it complies with current standards. This device measures consumption in a specific part of an installation without replacing the main meter. However, rules apply regarding its use for re-invoicing electricity. Generally, reselling electricity to a tenant is prohibited, except in specific cases like short-term rentals or campgrounds where it can help estimate a reasonable flat fee.
What are best practices for installing an electric sub-meter safely?
Installation of an electric sub-meter must be performed by a qualified electrician to ensure safety and compliance with NF C 15-100 standards. The professional will cut off the main power, mount the device on the distribution board’s DIN rail, connect phase and neutral wires according to the manufacturer’s diagram, and then verify proper operation. Proper expertise is necessary to prevent electrical or fire hazards.
How to use an electric sub-meter to set a flat fee?
The electric sub-meter does not typically allow direct billing of consumed electricity unless it is MID-certified and specific authorization is obtained. Usually, it serves as an informational tool to estimate consumption and determine a fair flat rate. In shared housing or furnished rentals, it provides an objective basis for setting charges, without issuing an actual electricity invoice.
What are the advantages of installing an electric sub-meter?
Installing an electric sub-meter offers several benefits. It allows precise monitoring of energy-intensive equipment like electric heating or a charging station. It facilitates equitable sharing of electricity costs in shared accommodation. In a professional setting, it supports energy efficiency initiatives. Finally, it helps identify the highest-consuming devices, enabling energy savings.
What budget should I plan for installing an electric sub-meter?
The cost of an electric sub-meter ranges from €20 to €300 depending on the model (single-phase, three-phase, connected). Installation charges by a professional add €70 to €200 depending on complexity. Connected models providing remote monitoring via an app are generally more expensive but offer better visibility into energy consumption.
Is an electric sub-meter suitable for a campsite or recreational area?
The electric sub-meter is especially useful in campsites or seasonal rentals. It helps estimate the electric consumption of rented accommodations, which can justify setting a flat fee. However, it cannot be used to bill accurately for actual consumption without special authorization. It remains a valuable tool for understanding vacationers’ habits and adjusting flat rates.
How to interpret data from an electric sub-meter?
Electric sub-meters typically display consumption in kWh. To calculate the consumption of a specific device or zone, note the displayed value at a given time and compare it to a later reading. The difference between readings indicates the amount of electricity used over that period. Some connected models offer advanced features such as real-time tracking, consumption statistics, and period analysis.
Is a individual electric meter mandatory in a dwelling?
Every dwelling must have a main electric meter, usually installed by the network operator (Enedis). This meter is essential for subscribing to an electricity contract and being billed based on consumption. The sub-meter is not mandatory; it is an optional accessory providing more detailed tracking of specific parts of the electrical system.
How to proceed to install a secondary electric meter?
To install a secondary electric meter, it is recommended to hire a certified electrician. The device is mounted on the distribution board’s DIN rail and installed upstream or downstream of the circuit to be measured. It must be protected by an appropriate circuit breaker. The electrician verifies the meter’s current rating (single or three-phase) and compliance with standards. After installation, a functional check is performed once power is restored.
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