Key points to remember: The electrical sub-meter measures the consumption of a specific circuit, allowing you to target energy savings and fairly distribute costs. This tool, accessible from 20€, is useful for shared housing as well as businesses, and helps to reduce carbon footprint. Its installation by a professional guarantees safety and legal compliance.
Are you having trouble identifying energy-consuming appliances in your home? The electrical sub-meter accurately measures electricity use by zone or device, such as a heating circuit or a floor. This device allows you to save up to 20% on your bill, fairly split costs between roommates, or set 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 while adhering to legal standards (mandatory MID certification).
- What is an electrical sub-meter and what is it used for?
- In which cases to use a divider meter?
- How to choose the right electrical sub-meter?
- Installing the sub-meter: a supervised and secure operation
- Legal framework: what you need to know about certification and refactoring
- Concrete benefits of sub-metering for your budget and the planet
What is an electrical sub-meter and what is it used for?
An electrical sub-meter, also called a divider meter or electrical deduction meter, is a supplementary 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 domain, or a dedicated circuit (heating, lighting).
Its use allows distinguishing the 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 appliances constitute a significant part of expenses.
It also serves to fairly distribute electricity costs in shared housing or co-ownership. In rental settings, it provides information on consumption related to the leased area, although direct refactoring is strictly regulated by law. For professionals, it contributes to energy management compliant with standards such as ISO 50001.
Two main types exist: the single-phase (up to 63A, MID certified) for typical residences, and the three-phase for industrial or highly energy-intensive installations. Although the Linky meter includes a similar function, a dedicated sub-meter offers more precise measurement for specific circuits.
In which cases to use a divider meter?
For precise monitoring of domestic consumption
A sub-meter isolates the consumption of energy-intensive appliances like heat pumps or charging stations. This allows adjusting their use according to variable rates (off-peak/peak hours) and optimizing costs. For example, a heat pump can represent a large part of the winter bill: the dedicated meter limits operation to low-cost hours.
It also monitors usage in an outbuilding or home office. For a professional, this distinguishes business consumption, justifying tax deductions. Detailed readings demonstrate the dissociation between domestic use and professional activity.
For fair distribution of charges
In shared housing, the sub-meter divides bills based on actual consumption, avoiding flat-rate sharing. It also applies to dwellings divided into separate zones (ground floor/upper floor), with one meter per part for transparent billing, even with very different uses (e.g., 24/7 occupancy vs occasional use).
In rental or professional use
For furnished rentals, it provides an objective basis to set justified fixed charges, respecting the law that prohibits direct re-invoicing (except for seasonal rentals). In companies, it supports energy efficiency initiatives (ISO 50001 standard) by measuring consumptions by zone or equipment. A business can identify high consumption items, facilitating targeted adjustments.
- Monitoring the consumption of energy-intensive equipment (heating, heat pump).
- Sharing electricity costs in shared housing.
- Assessing the consumption of a rented zone (studio, outbuilding).
- Identifying the consumption of a workshop or home office.
- Facilitating an energy efficiency strategy.
How to choose the right electrical sub-meter?
Choosing an electrical sub-meter depends on your installation and needs. Modern models offer advanced features to optimize energy management. Here are the key criteria to consider.
Single-phase or three-phase sub-meter: what’s the difference?
The single-phase sub-meter is suitable for typical domestic setups. It measures consumption on a 230V network with currents up to 63A. This type is appropriate for a standard house, apartment, or circuits such as lighting or electric heating.
The three-phase sub-meter is meant for high-power installations. It operates on a 400V network with currents over 80A. It is essential for equipment like heat pumps, industrial ovens, or when the distance between the meter and devices is significant. Note that this requires a main three-phase meter.
Advanced features of modern sub-meters
Connected sub-meters incorporate technologies like Wi-Fi or Modbus protocol (RS485). These options enable real-time monitoring via smartphone apps, such as Tuya or Smart Life. Some models include an internal relay to remotely control a circuit.
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 types of installations |
| Max. current | Typically 32A to 63A | Typically 80A or more | Variable (available in single-phase and three-phase) |
| Key features | Basic measurement of kWh | Measurement per phase or total | Real-time monitoring, remote control, double tariff, history |
| Price range (device) | 20€ – 80€ | 50€ – 150€ | 40€ – 300€ |
Sub-meters with double tariff (peak/off-peak hours) facilitate cost-effective consumption management. Brands like Legrand, Schneider Electric, or Delta Dore offer MID-certified models, essential for legal billing in professional contexts.
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 electrocutions. The NF C 15-100 standard requires a strict installation to ensure safety. For new or renovated work, a CONSUEL certificate is mandatory. Only professionals are qualified to meet these requirements, preventing unexpected costs.
Major steps in the installation
The process follows a strict protocol, carried out by a certified electrician:
- Shut off the main power supply via the main circuit breaker.
- Secure the sub-meter on the DIN rail of the electrical panel, upstream of the circuits to measure, verifying network compatibility.
- Connect phase and neutral cables according to the manufacturer’s diagram, respecting circuit breaker calibers.
- Verify operation after restoring power: test measurement thresholds (kWh, voltage).
What is the cost of a sub-meter and its installation?
The hardware costs between €25 and €300 depending on features (single-phase, three-phase, MID certified). MID-certified models are at the higher end. Professional installation costs between €100 and €200, including labor and ten-year warranty. For a complete setup, budget typically ranges from €150 to €300. These prices ensure compliance with standards and prevent unforeseen expenses. Costs may vary with complexity (e.g., connected meter).
Legal framework: what you need to know about certification and billing
The importance of MID certification
The MID (Measuring Instruments Directive) certification is an EU requirement ensuring the accuracy of energy meters used for commercial transactions. It is mandatory if the sub-meter data are used for financial billing.
A MID-certified sub-meter bears CE, “M,” and manufacturing year markings, with the certifying body’s code (e.g., “CE M08 1259”). This standard imposes strict tolerances (class B or C) to prevent measurement errors.
Non-compliance means unauthorized use for billing. It remains useful for energy monitoring without a financial stake.
Electricity refactoring: permitted or prohibited?
Law strictly prohibits reselling electricity at a rate higher than its purchase cost to tenants. This applies even with a sub-meter, as resale is reserved for licensed suppliers.
In long-term rentals, a landlord cannot issue invoices based on a sub-meter. However, for furnished or seasonal rentals, consumption can justify a fixed fee included in charges, without annual regularization.
In lease agreements, these rules are as important as clauses in your home insurance.
Uncertified sub-meters (not MID) are allowed to analyze consumption but not for precise billing. Consult an electrician or legal expert if unsure to avoid legal penalties.
Concrete benefits of sub-metering for your budget and the planet
The electrical sub-meter measures the consumption of a particular circuit or dwelling. This detailed tracking helps identify high-energy-consuming posts and save up to 30%, notably by isolating heating, air conditioning, or standby appliances. Data support habit adjustments or equipment replacements.
Distributing costs based on actual usage prevents conflicts among roommates or tenants. For example, a sub-meter on a rented studio allows billing only for the occupant, while ensuring fair charge management. It encourages responsible consumption through transparent data, motivating everyone to reduce their impact.
- Precise control of your energy budget.
- Fair and transparent cost sharing among occupants.
- Quickly identifying the most energy-hungry devices to optimize.
- Taking a step toward more responsible and ecological consumption.
Saving on your bills is a great first step to better manage your budget and savings daily. This approach also limits the carbon footprint associated with energy production, aligning with ISO 50001 principles. Combining the sub-meter with tools like energy management systems makes it possible to monitor consumption in real time, adjust habits, and plan savings, enhancing both financial and ecological impacts.
The electrical sub-meter enables precise control of consumption by isolating high-energy posts, fair cost sharing in shared living spaces, and optimizing bills. As an energy management tool, it balances financial savings and eco-friendliness by reducing waste, while facilitating responsible and informed electricity use on a daily basis.
FAQ
Is it legal to install an electrical sub-meter?
It is perfectly legal to install an electrical sub-meter, provided it complies with current standards. This device measures the electricity consumption of a specific part of an installation without replacing the main meter. However, certain rules apply regarding its use for billing. Generally, selling electricity to a tenant at a rate above its cost is prohibited, except in specific cases like short-term rentals and campgrounds, where it can serve as a tool to estimate a fair fixed fee.
What are the best practices for safely installing an electrical sub-meter?
Installing a sub-meter must be carried out by a qualified electrician to ensure safety and compliance with NF C 15-100. The professional will cut off the main power, fix the device on the DIN rail in the electrical panel, connect phase and neutral cables according to the manufacturer’s diagram, and verify proper operation. This process requires expertise to avoid electrical or fire risks.
How to use a sub-meter to set a fixed charge?
The electrical sub-meter does not allow for direct billing unless it is MID certified and a specific authorization has been obtained. Usually, it serves as an information tool to estimate consumption and establish a fair fixed fee. In shared housing or furnished rentals, it provides an objective basis to determine charges, without issuing a bill for electricity used.
What are the benefits of installing an electrical sub-meter?
Installing a sub-meter offers several advantages. It enables precise tracking of energy-intensive devices like electric heating or charging stations. It facilitates fair cost sharing in shared living spaces. In a professional context, it supports energy efficiency efforts. Finally, it helps identify the most power-hungry appliances, allowing energy savings.
What is the budget for installing an electrical sub-meter?
The price of a sub-meter varies between €20 and €300 depending on the model (single-phase, three-phase, connected). Professional installation adds approximately €70 to €200, depending on complexity. Connected models enabling remote monitoring via an app are usually more expensive but provide better oversight of energy consumption.
Is a sub-meter suitable for a camping site or recreational area?
The electrical sub-meter is particularly useful in campsites or holiday rentals. It allows estimating the electricity consumption of leased accommodations, which can justify a fixed charges fee. However, it cannot be used to bill actual consumption without special authorization. Still, it is a helpful tool to understand tourist consumption patterns and adjust fixed tariffs.
How to interpret data from a sub-meter?
Sub-meters generally display consumption in kWh. To calculate consumption for a particular device or zone, note the displayed value at a given moment and compare it to a later reading. The difference between the readings indicates the amount of electricity used over that period. Some connected models offer advanced features like real-time monitoring, consumption statistics, and period analysis.
Is an individual electricity meter mandatory in a dwelling?
Every dwelling must have a main electricity meter, usually installed by the network operator (Enedis). This meter is essential for contracting electricity and getting billed according to consumption. The sub-meter, on the other hand, is not mandatory. It is an additional device for more precise tracking of consumption in a specific part of the electrical system.
What is the procedure to install a secondary utility meter?
To install a secondary utility meter, it is recommended to hire a certified electrician. The device attaches to the DIN rail in the electrical panel and is installed upstream or downstream of the circuit to measure. It must be protected by an appropriate circuit breaker. The electrician verifies that the meter matches the circuit’s current capacity (single or three-phase) and conforms to current standards. After installation, a functionality check is performed once power is restored.
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