Two hardware versions are being developed:

  • Hestia32 HVAC - designed for standard 24 V AC HVAC systems, including multi-stage heating and cooling and heat pumps.
  • Hestia32 EU - designed for European mains-powered heating and HVAC applications.

The thermostat provides five configurable relay outputs, allowing it to control different combinations of heating stages, cooling stages, heat pumps, fans, humidity equipment and domestic hot water. The humidity output can be configured for either humidification or dehumidification.

A 3.5-inch IPS display provides the user interface, while an SHT45 temperature and humidity sensor provides accurate environmental measurements. Wi-Fi connectivity is currently used for local networking and MQTT and secure OTA updates allow the firmware to be updated without opening the enclosure.

The project is being designed with future expansion in mind. Additional connectivity options such as Thread, Matter and Zigbee are planned as firmware/OTA additions, without requiring a hardware replacement.

Everything needed to understand, build, modify and manufacture Hestia32 is intended to remain open: firmware source code, schematics, PCB layouts, bill of materials, manufacturing files, enclosure CAD files and documentation will be published as part of the project.

The goal is simple: build a thermostat that belongs to its owner rather than to a cloud service or a particular vendor ecosystem - and that can continue to be repaired, modified and improved long after it was purchased.

Follow the project

Hestia32 is currently in development, with a Crowd Supply campaign planned for the next stage of the project.

Follow the Hestia32 pre-launch page on Crowd Supply:

https://www.crowdsupply.com/makeopenstuff/hestia32

The pre-launch page will be updated as development progresses and will be the primary source for campaign and availability information.

Features

  • Fully open-source hardware and firmware
  • Standalone operation - no cloud service or subscription required
  • 3.5-inch display with an integrated touch interface
  • ESP32-C5-based controller
  • Accurate SHT45 temperature and humidity sensor
  • Five configurable relay outputs
  • Support for multi-stage heating and cooling
  • Heat pump support
  • Configurable fan control
  • Humidification or dehumidification control
  • Domestic hot water control
  • Local MQTT support
  • Future Thread, Matter and Zigbee support planned through firmware updates
  • Home Assistant, OpenHAB and Node-RED integration
  • Secure OTA firmware updates
  • HVAC and European mains-powered hardware versions
  • Open-source PCB, schematics and manufacturing files
  • Open-source 3D-printable enclosure
  • Designed for repairability and long-term ownership

Hardware

  • Controller: Seeed Studio XIAO ESP32-C5 and Generic ESP32-C5 DevKit option
  • Display: 3.5-inch 320 × 480 color display with resistive touch interface 
  • Temperature / humidity: Sensirion SHT45 
  • Relay outputs: 5 × configurable mechanical relays 
  • Connectivity: Wi-Fi, with local MQTT 
  • Firmware updates: OTA 
  • Power: Dedicated hardware for 24 V AC HVAC systems or European mains-powered systems

The five relay outputs are software-configurable, allowing the same hardware to support different HVAC configurations rather than requiring a different thermostat for every application.

The complete hardware design, including schematics, PCB layout, BOM and manufacturing files are already public during the development phase on the GitHub repo link below.