A connected thermostat does not improve a heat pump's efficiency, it corrects its control, and that gain has a number on it. Delegated Regulation (EU) No 811/2013 grades temperature controls from I to VIII and gives each a seasonal efficiency bonus carried on the package fiche: from 1 % for a plain on/off thermostat to 5 % for a multi-sensor control driving a modulating generator. That is the figure you can write down, not the 10 to 15 % savings quoted in advertising.
The question that decides the job comes earlier: does the generator accept a volt-free contact, a proprietary bus, or does it impose its own controller. Fitting a universal thermostat on a bus-controlled heat pump loses the weather compensation, the defrost management and usually the manufacturer's warranty, for a control gain that then falls back to class I.
Understanding the connected thermostat with a heat pump: what changes on the ground
Role of the thermostat: setpoint, programming and anticipating heat-up
With a heat pump, the thermostat doesn't just raise or lower the temperature. It sets a stable setpoint, manages time slots and, on connected models, can anticipate heating based on the home's thermal inertia. On the ground, the goal is to avoid sudden swings. A heat pump likes to modulate, not chain start-stop cycles.
The eight control classes and the bonus each one earns
The table below is what the package fiche is built on. It sets what you are allowed to claim, and it explains why two thermostats at the same price are not worth the same in the file. On the equipment side, Argile carries the seasonal efficiency and the verified characteristics of each reference in the catalogue.
| Class | What the control does | Seasonal efficiency bonus |
|---|---|---|
| I | On/off room thermostat | + 1 % |
| II | Weather compensator, modulating generator | + 2 % |
| III | Weather compensator, on/off generator | + 1.5 % |
| IV | TPI room thermostat, on/off generator | + 2 % |
| V | Modulating room thermostat, modulating generator | + 3 % |
| VI | Weather compensator plus room sensor, modulating generator | + 4 % |
| VII | Weather compensator plus room sensor, on/off generator | + 3.5 % |
| VIII | Multi-sensor room control, modulating generator | + 5 % |
Two practical consequences. A connected thermostat fitted to a heat pump whose weather compensation is switched off falls back to class I or V, never VI or VIII, however many screens the app has. And class VIII assumes several room sensors genuinely wired into the same control, which rules out an assembly of connected radiator heads that exchange nothing with the generator.
Compatibility with air/water, air/air heat pumps: points to check before installing
Before installing, check how the heat pump is controlled. Some accept a simple contact, others require a manufacturer interface. On air/water systems, also look at the heating curve, the type of emitters (underfloor heating or radiators) and how summer mode is managed if the heat pump is reversible. On air/air systems, the thermostat often has to go through the original controller. It's best to aim for a native controller when possible.
Room-by-room control: when it's worthwhile and when it complicates things
Room-by-room control is worthwhile in a multi-storey or very exposed house, with different usage patterns. But multiplying zones can complicate the hydraulics on air/water systems. Risk of too low a flow rate, short cycling, or discomfort on underfloor heating. In those cases, a clean overall setting and careful balancing often work better than stacking up accessories.
Choosing the right thermostat for a heat pump: simple criteria, no unpleasant surprises
Wired or wireless thermostat: reliability, range and site constraints
In renovation, wired remains the most reliable: no batteries, few dropouts, and a stable reading. It does require running a cable, which is simpler on a heavy renovation job. Wireless is quicker to install, but check the actual range (load-bearing walls, slab, distance), battery life and signal quality before closing everything up.
Relay, home automation gateway and app: what the customer really needs
A heat pump doesn't always accept just any thermostat. Depending on the brand, you need a relay (dry contact) or a module compatible with the manufacturer's bus. The gateway and app are useful if the customer wants to control remotely, track setpoints and receive alerts. Keep cloud-free operation possible, just in case.
Zone and valve management: avoiding incompatibilities
If you're zoning the system, check the thermostat's compatibility with the valve actuators (24V or 230V) and the number of zones. With a heat pump, closing too many loops can cause short cycling. Plan for a minimum flow rate, a bypass or a buffer tank if needed, to stay on the comfort side.
Settings and configuration: getting a stable, efficient heat pump with a thermostat
Heating curve: basic settings to avoid sudden swings
Start by enabling the heating curve. Set a fairly low curve, then fine-tune it in small steps over a few days. The thermostat mainly serves as a fine correction, not an on/off button. Avoid large day/night swings. A stable setpoint helps the heat pump modulate, with fewer restarts and better efficiency.
Thermal inertia, hysteresis and short cycling: limiting wear and noise
With underfloor heating or cast-iron radiators, thermal inertia is your ally. Set the thermostat's hysteresis around 0.3 to 0.5°C to avoid short cycling. If the heat pump starts and stops too often, lower the slope, limit the flow temperature and give the house time to stabilise. The goal: long, quiet operating phases.
Away and frost-protection modes: securing the home without overconsuming
When away, lower the setpoint by 1 to 3°C rather than switching off. Enable frost protection (often 8 to 10°C) to protect the pipework. Also check hot water programming, to avoid unnecessary reheating. A connected thermostat can simplify the return home. You keep comfort, without heating an empty house.
Home automation and remote control: practical uses and limits to explain
Useful home automation scenarios: schedules, presence, shutters and temperature
With a connected thermostat, the most useful scenarios are simple. Time-based programming, automatic night setback, reheat before returning home. Absence detection or holiday mode to avoid heating for nothing. Roller shutters that close at sunset and limit heat loss, then open in the morning to make the most of solar gains. The goal is real gains, not just a dashboard.
Consumption data: what the thermostat really shows (and what it doesn't tell you)
The thermostat mainly displays setpoints, time slots and running time. Some apps estimate kWh or euros, but without a dedicated meter it's an approximation. It doesn't tell you the heat pump's actual performance, nor room-by-room comfort variations. To be sure, cross-check with bills, Linky readings and, if needed, more reliable monitoring.
Security and network: good Wi-Fi and remote access practices in 2026
In 2026, the rule stays the same. Secure the Wi-Fi with WPA2 or WPA3, a long password, a guest network or a network dedicated to connected devices. Automatic updates, removal of default credentials, and two-factor authentication on the account. For remote access, avoid opening ports. Favour a well-maintained manufacturer service or a VPN, that's the right approach.
Grants and compliance: what you need to get right to stay solid in 2026
Impact on MaPrimeRénov' and CEE: when the thermostat counts in the application
Depending on the pathway, the thermostat can be a CEE-funded operation, or an element expected to justify consistent controls after a heat generator change. Argile is connected to the CEE providers and computes the incentive inside the financing plan. In the application, keep a detailed invoice and, if needed, the reference to the associated standardised operation sheet.
RGE and traceability: proof of installation, commissioning and settings
On the compliance side, what protects the job is the paper trail. Prepare a simple evidence pack: installation photos, wiring diagram, commissioning report, settings applied, and date. For connected systems, also note the pairing and the access credentials handed over.
Customer information: manual, usage instructions and commitment on savings
Hand over the manual and a usage sheet, programming instructions, recommended temperatures, away modes, and who to call in case of a fault. State estimated, not guaranteed, savings, since the saving depends on the home, occupancy and the settings used.
