ESPHome Altherma - Monitor your Daikin Altherma 3 heat pump via X10A

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Hello :waving_hand:

Sharing my ESPHome custom component for monitoring Daikin Altherma 3 heat pumps via the X10A connector. Inspired by ESPAltherma, but built as a native ESPHome component, so it integrates directly with Home Assistant.

Github: github.com/jjohnsen/esphome-altherma
Web install: jjohnsen.github.io/esphome-altherma

Features

  • Browser-based installation flash directly from your browser via ESP Web Tools
  • Temperature monitoring outdoor air, discharge pipe, heat exchanger, leaving water, inlet water, DHW tank, etc
  • Electrical sensors inverter current, voltage
  • Operational data compressor frequency, fan speeds, flow rate, water pressure, pump signal
  • Binary sensors defrost status, thermostat ON/OFF, silent mode, freeze protection, 3-way valve, BUH steps
  • Diagnostics operation mode, error codes and sub-codes
  • Multiple board support ESP32, ESP32-S3, M5Stack AtomS3 Lite
  • Model-specific configs modular YAML files per heat pump model
  • Mock UART mode for development/testing without hardware

Supported Hardware

Any ESP32 board with an UART, tested with:

  • Generic ESP32 DevKit
  • ESP32-S3 DevKit
  • M5Stack AtomS3 Lite
  • Old M5Stack

Wiring is just 4 wires to the X10A connector (5V, TX, RX, GND). No soldering required if using Dupont connectors.

Screenshots

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image1031×1003 93.1 KB

Currently Supported Models

  • ERGA-D EHV/EHB/EHVZ DA series (04-08kW)
  • Community-contributed EHVX configs

Happy to answer any questions!

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Quick follow-up, even though my original post did not generate much discussion :wink:

The project has moved forward quite a bit, and ESPHome Altherma is now in active use by multiple users across more Daikin models and several ESP32 board variants.

Version 1.1.0 is out, and it adds:

  1. Experimental Register Discovery
    You can now use the Home Assistant action query_register to test registers directly and discover model-specific data points.

  2. Emoncms guide and Home Assistant blueprint
    I published a full setup guide for long-term monitoring with MyHeatpump dashboards:
    https://jjohnsen.no/2026/esphome-altherma-emoncms-setup-guide/.

Previous releases also added OTA updates and better stability by replacing the blocking UART polling loop with a non-blocking state machine. In practice, this makes the component more robust under load, especially in setups with extra sensors or less stable UART timing.

The MyHeatpump app gives you a practical way to track your heat pump’s performance over time, including COP, heat output, electricity use, and temperature trends.

ESPHome Altherma running on M5Stack Basic
ESPHome Altherma running on M5Stack Basic838×589 89.7 KB

ESPHome Altherma running on M5Stack Basic.

ESPHome Altherma + Emoncms and My Heatpump App
ESPHome Altherma + Emoncms and My Heatpump App838×483 85.4 KB

ESPHome Altherma + Emoncms and My Heatpump App

Still happy to answer any questions :wink: