Dewpoint Calculator for Home Assistant

A custom integration for Home Assistant that calculates the dewpoint based on temperature and humidity sensors.

What is dewpoint?

The dewpoint is the temperature at which air becomes saturated with moisture and water vapor begins to condense into liquid water (dew). It's a key indicator of humidity and comfort levels in your home.

Why is this useful?

• Mold Prevention: When surfaces in your home (walls, windows, etc.) fall below the dewpoint temperature, condensation forms, creating ideal conditions for mold growth. By monitoring the dewpoint, you can take preventive action.
• Comfort Assessment: Unlike relative humidity, dewpoint provides an absolute measure of moisture in the air. A dewpoint above 20°C (68°F) feels muggy, while below 10°C (50°F) feels dry and comfortable.
• Climate Control Optimization: Understanding dewpoint helps you optimize your heating, cooling, and dehumidification systems to maintain a healthy indoor environment.
• Window Condensation: Compare room dewpoint with window surface temperatures to predict and prevent condensation issues.

How does it work?

This integration uses existing temperature and humidity sensors in your Home Assistant setup to automatically calculate and display the dewpoint as a new sensor entity. The calculation updates whenever your source sensors change, giving you real-time monitoring of moisture conditions.

Installation via HACS

HACS (Home Assistant Community Store) makes it easy to install custom integrations. If you don't have HACS yet, install it first from hacs.xyz.

1. Open HACS in Home Assistant
2. Go to Integrations
3. Click the three dots in the top right corner
4. Select Custom repositories
5. Add the repository URL: https://github.com/sebastian-software/ha-dewpoint-calculator
6. Select category: Integration
7. Click Add
8. Search for Dewpoint Calculator and click Download
9. Restart Home Assistant to complete installation

Manual installation

If you prefer not to use HACS:

1. Download the latest release from the releases page
2. Copy the custom_components/dewpoint_calculator folder to your config/custom_components/ directory
3. Restart Home Assistant to complete installation

Note: Your final path should be config/custom_components/dewpoint_calculator/manifest.json

Creating a dewpoint sensor

After installation, you can create one or more dewpoint sensors. Each sensor requires an existing temperature sensor and humidity sensor as data sources.

1. In Home Assistant, navigate to Settings → Devices & services
2. Click the Integrations tab at the top
3. Click the + Add Integration button in the bottom right corner
4. Search for and select Dewpoint Calculator
5. Enter a descriptive name for your sensor (e.g., "Living Room Dewpoint")
6. Select the temperature sensor you want to use as a source
7. Select the humidity sensor you want to use as a source
8. Click Submit to create the sensor

Tip: You can repeat these steps to create multiple dewpoint sensors for different rooms or areas in your home.

License

Apache License; Version 2.0, January 2004

Copyright

Copyright 2025–2026
Sebastian Software GmbH