OpenTherm Thermostat 2

€ 40.00

Smart OpenTherm Thermostat with Home Assistant integration. Compatible with all OpenTherm boilers. Remote control over WiFi. An energy saving room thermostat with a remote sensor and weekly schedule helps you cut energy costs and level up home comfort.


Shipping from the EU.

Smart Room
OpenTherm Thermostat

The Smart OpenTherm Thermostat is a great way to save energy, improve comfort, and add convenience to your home. If you are looking for a way to improve your home's heating system, it is a great option.

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Key Features

With OpenTherm Thermostat ability to optimize heating systems, remote access, customizable schedules, and integration with other smart home devices, it's a must-have for modern homeowners.

Energy savings & comfort

Smart OpenTherm thermostat can help you save energy by communicating with your boiler to adjust its output based on the current room temperature. This allows the boiler to operate more efficiently, as it only needs to produce as much heat as is necessary to maintain the desired temperature. It keeps a consistent room temperature and compensates for changes in the outside temperature.

Remote Access & Control

Central heating thermostat can be controlled remotely via web interface or home automation integration, so you can adjust your heating from anywhere. This is especially useful if you are away from home.

Integration with Smart Home Systems

The Smart Thermostat has Home Assistant integration which gives you remote control via Home Assistant application. Home automation, heating schedule using scenarios.
In general, you can integrate the smart thermostat into any home automation system using MQTT protocol

OpenTherm Thermostat Remote Controll

OpenTherm Thermostat Connection

The OpenTherm thermostat connection is made as simple as possible

OpenTherm Thermostat Connection

Just use 2 wires for the boiler connection (find OT terminal block on the boiler and Boiler terminal block on the thermostat) and a USB Type-C charger as a power source.

More Features

By investing in this smart technology, you not only make your daily life more comfortable but also contribute to a greener and more sustainable future.

OpenTherm Thermostat Schedule

Customizable Schedules

The smart thermostat allows you to create personalized heating schedules that align with your daily routine. You can set different temperatures for various times of the day or week, ensuring that your home is always comfortable when you need it to be.

OpenTherm boilers compatibility

OpenTherm Thermostat is compatible with all boilers those have OpenTherm protocol support.
The smart home thermostat works with all versions of the OpenTherm protocol.

Easy installation & Configuration

Just connect the thermostat to a boiler using 2 wires and power via any USB Type-C power adapter. Use WiFi Manager to setup WiFi connection. Choose an appropriate room temperature sensor.

DIYLESS Thermostat Controls

Smart Thermostat Controls


  • Switch thermostat mode/screen CH - central heating mode, DHW - domestic hot water preparation mode, System - system information
  • Switch heating mode - Auto (smart heating control), Manual (manual boiler setpoint), Off (turn off central heating)
  • Reset hole - can be used to reboot thermostat
  • Up button - increase setpoint (long press - quick change)
  • Down button - decrease setpoint (long press - quick change)

Smart Thermostat Display

Smart Thermostat Display


  • Thermostat IP address can be used to access the thermostat web interface using web browser
  • Room current temperature - current ambient temperature in the room where the smart thermostat is installed.
  • Room target temperature - the temperature your thermostat is set to (setpoint)
  • Thermostat state - Heating (flame on), Idle (flame off), Off (the thermostat is turned off)
  • Heating mode - Auto (smart control), Manual (set boiler setpoint), Off (turn off the thermostat)
  • OpenTherm state - OpenTherm connection is active
  • Bluetooth state - Bluetooth connection with temperature sensor is active
  • WiFi state - WiFi connnection is active
  • Thermostat mode - Central heating, Domestic Hot Water, System information

WiFi Thermostat Web Interface

WIFI OpenTherm Thermostat Interface


  • Wi-Fi Thermostat Web interface. Access using web browser by the thermostat IP address:
  • Central heating control page (Auto, Manual, Off modes).
  • Domesting Hot Water preparation page (On, Off modes)
  • Schedule page. Enable/disable shedule, select time zone, add weekly setpoints for each day
  • Configuration page. MQTT, OpenTherm, heating control, temperature sensor settings...

Thermostat Home Assistant Integration

OpenTherm Thermostat Home Assistant


  • Home Assistant application. Web access for desktop or native mobile application for iOS or Android.
  • Easy to add central heating and DHW cards using Home Assistant auto discovery feature
  • Detailed thermostat state and control over MQTT protocol
  • MQTT remote temperature sensor option

Popular Questions

In order to use the thermostat you will need to configure at least WiFi connectivity first.
For configuration manual please refer to the Initial thermostat configuration page.
We use Standard International Shipping method, usually it takes about 12-15 days and costs €5.5
Shipping from the EU, no additional fees for the EU countries. If you are outside the EU taxes of your country will apply.
Stock firmware is not open source, but you can write your own firmware adding new cool features that fits your needs the best. DIYLESS Thermostat is based on Espressif's ESP32 Soc, which enables BLE/WiFi connectivity and allows writing a firmware using Arduino IDE, VS Code or IDF (Eclipse) IDE.
Also you can use ready-made firmwares like ESPHome, Tasmota etc.

If the stock firmware fits almost all your needs and only a few feature(s) are missing - we can consider adding them to the next version, please report a request or an issue report into our thermostat repo. Subsequent updates are free, and if you experiment on your thermostat with a custom firmware and later decide to rollback to the original one - we have a simple browser-based tool which allows you reverting back to the stock easily.
We use a PI algorithm which calculates the needed boiler power level based on a difference between current and target room temperature and also takes into account the speed at which this temperature rises/drops. It is aimed for the best comfort, meaning less temperature fluctuations.
That means the boiler will spend more in active state however at a lower power level instead of cycling between max power and off.
No, with a current control algorithm implementation you would not need a knowledge on outside temperature, because thermostat senses an internal temperature and once it drops - boiler will rise radiators temp to compensate.
In practice (from a real installation) - room temperature accuracy is held within a ±0.15°C range.
Yes, it does. However to use it properly - you will need to distance it from a board using a wires, since ESP32 self-heats a lot and sensor is heated by the board.
Out of the box it is controllable within your home network. If you need world-wide controlling options - one of the possible ways to achieve this is a Home Assistant with its companion app.
A first option is using a 5V wall brick adapter and a Type-C cable.
Also you can checkout if your thermostat revision has a dedicated 5V pads near a USB connector (named H1). If so - provide a DC power of 4-5.5V, square pad is positive terminal. blank

Another option would be using an internal UART pads. Provide a voltage in range 3-3.3V here. blank

Exceeding the values above may permanently damage your device.

Enjoy With Room Thermostat

This room thermostat is just as smart as other well-known smart thermostats, but comes at an affordable price. So, take control of your heating system and embrace the benefits of a DIYLESS Smart OpenTherm Thermostat today.

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