Climate Cleanup

This post is about the upcoming changes for the Home Assistant climate integration. These changes are being implemented right now and are no longer up for discussion. If you want to see changes, consider opening an architecture issue.

Starting with Home Assistant 0.96, we're shipping a big architectural clean up of our climate integrations. This effort is lead by Pascal Vizeli.

Over the years, the climate integration has grown from being a simple place for thermostats to hosting ACs, heat pumps and ventilation systems. During this growth, mistakes have been made which resulted in a confusing and hard to work with design. Work is underway to get this all cleaned up and we're going to ship this in Home Assistant 0.96.

The biggest mistake we made is that we conflated operating and operation mode. Operation mode is what you want your thermostat to do, for example, heat the house to 19 °C. The operating mode is what the thermostat is currently doing. Is it heating because the house is too cold? Or did it already reach the target temperature and is it currently idle?

On top of that, we've noticed that a lot of integrations overload operation mode with a wide range of delightful options like "eco", "comfort", "boost" or "sleep". After carefully analyzing all the different climate systems out there, we have come to the conclusion that these alternative operation modes are variations of the existing operation modes (heat, cool, heat-cool), but might have different target temperature ranges or try to heat/cool at a slower pace to conserve energy.

To support as many different thermostats as possible, we have decided to allow climate devices to specify a new "preset" mode that they are operating under. It covers hold mode, away mode, or any custom operation mode that a thermostat includes.

You might wonder, why go for a preset instead of allowing to overload operation mode? On first glance, it might seem fine for an integration to list the possible options and the current chosen option, easy to make a UI for. However, that's not the only way Home Assistant is used. We are also serving as a single place to control any thermostat for external systems like Google Assistant or Amazon Alexa. They have a limited set of operation modes they expect.

A gist of the changes:

• operation_mode has been renamed to hvac_mode to emphasize what the mode is for.
• We split HVAC mode auto into auto and heat_cool. If it's heat_cool, the user has set a temperature range the device has to use heating and cooling to stay within. Auto mode is now limited to devices that are running on a schedule or AI.
• The state of a climate entity is now always equal to the HVAC mode.
• hvac_action is introduced for integrations that know the current action: heating, cooling, idle.
• set_away_mode and set_hold_mode have been merged into set_preset_mode. So instead of turn_away_mode_on(), we will now call set_preset_mode("away").
• The is_on property has been removed. If a device is able to turn off, it should include the hvac mode HVAC_MODE_OFF.
• Property names have been aligned, anything ending with "_list" is now named "_modes".

If you are a maintainer of an integration that has a climate platform or maintain a custom component that has one, make sure you follow the pull request and test your integration during the beta to make sure that it works like expected.

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