This separation between the moment when we heat and when we use the water interests Elax Énergie. The company installs a connected thermostat on existing tanks to answer two questions: how much heat should be prepared for residents, and when should the necessary electricity be consumed?
The first should make it possible to reduce household expenses. The second opens up economic activity on the scale of the electricity system.
Avoid heating more than necessary
In a home, hot water needs change with the number of occupants, their schedules or their absences. A fixed setting does not necessarily take these variations into account. The tank can thus maintain a reserve at a higher temperature than necessary to cover uses.
However, even insulated, a water heater gradually loses heat. Electricity is used to heat the water used, but also to compensate for these losses. Adjusting operation to needs can therefore reduce consumption, provided that a sufficient reserve is preserved and health requirements are respected.
This is the first function of the Elax box. According to the company, it can be installed in around twenty minutes on the existing device and communicates via a mobile connection, without using the home’s Wi-Fi. After a phase of observing habits, it adapts the temperature and heating cycles.
Elax claims savings of 20 to 25% on water heater consumption. This figure only concerns hot water production, and not the entire household electricity bill. The gains depend in particular on the initial setting and the uses of the occupants.
To calculate them, the company compares the consumption measured with its device to an estimate of what the balloon would have consumed without piloting. She indicates that she developed this method with Carbone 4.
Prepare water when electricity is abundant
The second function consists of choosing the heating times. The principle already exists with off-peak hours: a contactor triggers the balloon on times provided for in the electricity contract. Elax seeks to make this organization more adaptable.
Let’s take a home whose inhabitants mainly use hot water in the evening. If the reserve and equipment permit, the tank can heat up in the early afternoon, during a period of abundant solar production. It then keeps the water hot until needed.
Conversely, when electrical demand is high, a tank that still has enough hot water can wait before restarting. The resident keeps his shower schedule, while the consumption of his device is shifted.
Heating a room also offers offset possibilities, particularly in a well-insulated building. But comfort depends directly on the interior temperature. The balloon has a heat reserve intended for later use. This property facilitates the organization of its consumption.
Why the electricity network can pay for this service
At every moment, the electricity system must balance production and consumption. When many devices start together, there must be enough production to meet demand. At other times, available electricity is more abundant than needed.
Shifting part of the consumption helps bring these two curves closer together. A single water heater represents a little wiggle room. Thousands of coordinated devices can form a set large enough to participate in electricity markets.
This is what the sector calls “flexibility”: the ability to temporarily modify consumption. Elax brings together that of numerous housing units and values it according to the market mechanisms to which it can access. The thermostat gives it the means to act on the devices; their coordination constitutes the economic service.
This income can contribute to financing pilotage. Thomas Tirtiaux, director of Elax, explained in a public speech that remuneration for flexibility had made it possible to eliminate the subscription previously charged to lessors for the control of water heaters.
However, the equipment, its installation, the connection and the maintenance still have a cost. The balance of the model therefore depends on the revenue that each device can generate during its operating life. The press release does not specify either this income or the full cost of equipped accommodation.
Social landlords allow thousands of devices to be deployed
Elax has developed its activity with social landlords. These organizations manage large housing stocks and can organize equipment programs on a scale that is difficult to achieve by approaching individuals one by one.
Their interest relates both to tenant charges and to the maintenance of the property. The box should make it possible to better adjust the water heaters, but also to collect information on their operation to identify anomalies and prepare for interventions.
The RIVP notably announced in 2025 a program involving more than 22,000 water heaters. This volume corresponds to an equipment program, to be distinguished from the installations actually carried out. In its October 2026 press release, Elax claims nearly 100,000 equipped housing units in total, more than 100 partner landlords and 58 employees.
Competition over how to manage housing
Elax is not alone in wanting to organize the consumption of domestic equipment. Voltalis manages several electrical uses, including hot water tanks. Octopus Energy also offers water heater control via Linky, without adding a box in eligible homes.
These approaches place a question at the center of the competition: what value does additional equipment installed on the balloon provide? For Elax, the answer lies in adjusting the temperature, knowing needs and monitoring maintenance, in addition to moving schedules.
These benefits must justify the cost and organization of an intervention in each home. In this electricity consumption management market, the quality of service to residents is as important as the ability to coordinate devices.
Two new markets to organize
Elax now wants to reach more individuals thanks to Elax Pro, a network of building tradesmen. Plumbers, electricians and heating engineers must become a relay to propose and install their solution. This development requires training professionals, controlling installation and maintaining support adapted to a more dispersed clientele.
The company also plans to extend its activity to collective boiler rooms. This involves adding electricity production to an installation running on gas, in order to switch part of the heat production to electricity when conditions are suitable.
This extension introduces additional constraints: sizing the equipment, having the necessary connection and financing the installations. The savings will then depend on the cost of the work, the respective prices of gas and electricity and the way in which the boiler room will be operated.
In individual housing as in collective buildings, Elax must maintain the same priority of use: having hot water available when residents need it. The possibility of staggering the heating begins with this available reserve.
Developed around Jean-François Eggericx, Thomas Tirtiaux and Samuel Beaussier, Elax Énergie announces a fundraising 30 million euros from Noria and the Environmental and Solidarity Revolution Fundmanaged by Crédit Mutuel Impact and supplemented by the societal dividend from Crédit Mutuel Alliance Fédérale. The funding must support the deployment in social housing, the launch of Elax Pro and the partial electrification of collective boiler rooms. The company also plans 30 recruitments by the end of 2027.
