which connected thermostat to buy for winter 2021?

Image 1: Connected thermostat: which is the best model to buy for winter 2021?
Netatmo Smart thermostat – Credit: Netatmo

When winter arrives, the main goal of most homes is simple: to improve thermal comfort while reducing energy bills. To do this, the connected thermostat, which allows you to control your heating from home or outside, appears to be an attractive solution. In this guide, we have tested several models in order to select the best connected thermostats for you.

Connected thermostats: the latest news

In early 2021, the French brand specializing in door chimes and video phones, Advisen, launched into connected home automation and released its first connected thermostat: the HomeFlow WL. It can be wired or battery-powered and allows you to control the temperature of your home remotely. It is compatible with gas and oil boilers and non-reversible heat pumps. On the market recently, it is particularly for its low price: only € 69 including tax in wired and € 89 wireless! However, we are waiting to test it to see if, for this price, it has its place in our ranking.

What are the best connected thermostats?

✅ The On / Off or OpenTherm command
✅ Advanced functions (calculation of thermal inertia, etc.)
❌ The price of the kit for electric heating

This thermostat benefits from many advanced functions: On / Off or modulating control via OpenTherm, learning the thermal inertia of the dwelling to optimize the rise or fall in temperature, detection of an open window, etc. The starter kit contains a Zigbee / Wifi gateway to be connected to the boiler. Thermostatic heads are available as an option to customize the temperature room by room. Another kit, more expensive, is planned for electric heating.

✅ The Auto-Adapt function
✅ Evolution over the versions
❌ The basic On / Off command

It is one of the oldest connected thermostats on the market. It has improved over the years with the arrival of new functions, such as Auto-Adapt (taking into account the insulation and the outside temperature to anticipate). Thermostatic heads can be added. This thermostat works basically in On / Off mode, but another version, released this fall and more expensive, allows the modulating boilers to be controlled via the OpenTherm language.

✅ The designs
✅ Many features
❌ The price of the wireless version

It is a fairly designer thermostat and also fairly complete: taking into account the thermal inertia of the home, humidity probe, modification of the hysteresis, detection of an open window… Please note, there is a wired version and a wireless version. wire, the latter being a little more expensive because accompanied by a radio relay.

✅ Multi-zone control support
✅ The many features
❌ Wireless installation which requires an extension kit

This thermostat by German Tado is one of the most advanced at the moment. It learns the thermal characteristics of the home and takes into account multizone control (via thermostatic head or additional thermostat), OpenTherm and certain proprietary protocols for modulation. Wireless installation requires an expansion kit.

What’s the point ?

A connected thermostat plays the same fundamental role as a classic room thermostat: it acts on the operation of the home heating generator, typically the boiler, so that the temperature reaches the value set by the user.

But its IP connection gives it some interesting additional functions: remote control through the smartphone and a mobile application, switching off and starting up the heating according to the user’s geographical position, learning the habits of residents for a suitable temperature in any circumstance, algorithm that calculates the thermal inertia of the home, monitoring of energy consumption …

There is also the hourly and calendar programming, already seen on a programmable thermostat, but easier to understand on the screen of a smartphone.

Does it work with all heating systems?

These thermostats operate with heating systems individual the most common: boiler (gas, oil, wood / biomass), heat pump, underfloor heating, etc. They can also control collective heating if there is a possibility of regulation.

Their action is most often binary (switching on and off of the boiler), more rarely modulating, which is more effective because the temperature in the water circulator is continuously adjusted to improve operation and the perceived comfort.

Recent thermostats (Nest v3, Tado v3 +, Netatmo Thermostat Modulating) take into account the standard language OpenTherm or control protocols specific to Atlantic, Saunier Duval, elm Leblanc equipment, etc.

When purchasing a recent model of boiler, however, it is preferable to opt for the thermostat from the same manufacturer., certainly more expensive but more and more connected and making the most of the intelligence of the boiler.

Image 10: Connected thermostat: which is the best model to buy for winter 2021?
The most recent connected thermostats are compatible with OpenTherm and some proprietary protocols. The control of the boiler is then more precise. Credit: Somfy

Electric heating is not as well taken care of, in particular radiators controlled by pilot wire, a French peculiarity. However, the Qivivo thermostat (now owned by Comap) exists in a version adapted to the pilot wire. Schneider Electric, likewise, offers a version of its thermostat for this type of heating.

The latest Nest models are also compatible, provided you go through an electrician. And Netatmo has developed with the Muller group radio modules to control the brand’s radiators.

How does it set up?

The principle is to connect the control organ, namely the thermostat, to the heating unit and to establish the Internet connection, via an IP gateway which communicates with the box.

Replacing an existing wired thermostat is the simplest case : this involves locating the two control wires (dry contacts, voltage free) coming from the boiler and then reconnecting them to the new thermostat.

Power is supplied by a set of batteries. Then, the Wifi gateway is plugged into an electrical outlet, at Somfy and Netatmo in particular, or directly on the Ethernet port of the Internet box (Tado).

Image 11: Connected thermostat: which is the best model to buy for winter 2021?
The IP gateway is connected to an electrical outlet or directly to the Ethernet box, depending on the thermostat model. Credit: Netatmo

If the existing thermostat communicates by radio, the connected replacement thermostat must be accompanied by a radio receiver (Somfy radio thermostat for example), which may be available as an option (Tado extension kit).

Then it is necessary remove the radio relay current, near the boiler, then reconnect the control and power cables to the new one. The IP gateway is installed as before. Those of Netatmo and Schneider Electric also act as radio receiver for the boiler if necessary.

In the event that the boiler does not have a relay or a thermostat, the boiler cover must be opened and the radio relay control and power cables must be connected to the boiler terminal block. People angry with screwdrivers and DIY in general can turn to a professional heating engineer.

Can we control the heating in several rooms?

If the central heating serves at least two independent heating circuits, the first option is to install one thermostat per zone. Tado, for example, offers additional thermostats, dedicated to multizone control.

At Nest, Tado, Netatmo and Schneider Electric, thermostatic heads (communicating by radio), to be placed on radiators, are also a means to individualize the temperature room by room. An interesting solution in a collective heating situation, with nevertheless independent radiators.

Image 12: Connected thermostat: which is the best model to buy for winter 2021?
A thermostatic head is used to individualize the temperature of a room. It communicates with an IP radio relay and can operate independently of a thermostat. Credit: Tado

Does it fit into a home automation system?

These thermostats, for the most part, can communicate with the IFTTT platform and services Google Home, Amazon Alexa and Apple Homekit. Voice control and connection with other connected objects or home automation boxes are therefore possible.

Somfy’s thermostat is additionally supported by the Tahoma box from the same manufacturer. That of Netatmo can also be controlled by the home automation application Celiane with Netatmo, from Legrand.

What savings are the key?

Heating accounts for two-thirds of a household’s energy consumption, according to Ademe, and the connected thermostat, well configured, is certainly welcome to reduce the bill. The most reasonable studies suggest savings of 5 to 15%, while some manufacturers are even more enthusiastic. This estimate should be qualified because it generally takes as a reference a heating system without any regulation.

A connected thermostat is eligible for a tax credit, which can accelerate its amortization. But the intervention of a certified professional RGE (Recognized guarantor of the environment) is required. Since July 1, 2020, a “boost” of 150 € to encourage the installation of a programmable thermostat has also been implemented. Here again, a professional (signatory of the “Boost Thermostat with efficient regulation” charter) must provide the service.

Frédéric Monflier

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