Thermostat mode changed

The Thermostat mode changed trigger fires after the HVAC mode of a climate entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more] changes. Climate entities include thermostats, air conditioners, heat pumps, and evaporative coolers. The HVAC mode determines what the device is set to do: Off, Heat, Cool, Auto, Dry, Fan only, or Heat/Cool. Use this trigger when you want to react to the user changing the device’s operational mode, regardless of whether it is actively heating, cooling, or idle.

Note: The UI labels this trigger as “Thermostat,” but it works with all climate entities.

You choose one or more modes, and the trigger reacts when the thermostat switches to one of them.

Using this trigger from the user interface

If you prefer building automations visually, Home Assistant walks you through this trigger step by step. You pick what to watch, tweak a few options, and save. No YAML knowledge required.

To use Thermostat mode changed in an automation:

1. Go to Settings > Automations & scenes.
2. Open an existing automation, or select Create automation > Create new automation.
3. In the When section, select Add trigger.
4. Select what you want to monitor. Under By target (see Targets), pick the area your thermostat is in (like your bedroom or living room). You can also select a device, a specific entity, or a label.
5. From the triggers shown for that target, select Thermostat mode changed.
6. Under Modes, select one or more modes you want to monitor.
7. Under Trigger when (see Behavior), pick Each, First, or All to control how the trigger behaves when multiple thermostats are targeted.
8. Under For at least, set how long the thermostat must remain in the new mode before the trigger fires. Leave it at zero to fire immediately.
9. Select Save.

Options in the UI

Using this trigger in YAML

If you work directly in YAML, or you want to know exactly what Home Assistant does under the hood, this section has the technical reference. It lists the field names you use in YAML, their types, and which ones are required. For how an automation is built in YAML, refer to Automations in YAML.

In YAML, put the settings that are specific to this trigger under options. Keep target, if the trigger uses one, and general settings such as id, alias, enabled, and variables at the top level, next to trigger.

When this trigger starts an automation, it passes data about what happened to the automation. You can use this trigger data in the templates of your conditions and actions. To see which data is available, refer to Trigger data in templates.

In YAML, Thermostat mode changed is referred to as climate.hvac_mode_changed. A basic example looks like this:

trigger: climate.hvac_mode_changed
target:
  entity_id: climate.living_room
options:
  hvac_mode: "heat"

This reacts when climate.living_room switches to the Heat mode.

Options in YAML

Targets of the trigger

This trigger requires a target. The target is the object that Home Assistant will watch. You can select a single entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more], a device, an area, a floor, or a label as a target, and Home Assistant will watch every matching climate entity behind that target.

• Entity: one specific climate entity, such as climate.living_room.
• Device: every climate entity that belongs to a device.
• Area: every climate entity in a room or area.
• Floor: every climate entity on a floor.
• Label: every climate entity that shares a label.

You can also select different target types in one trigger. For example, you can add a specific entity and an area as targets in the same trigger to monitor both of them at once.

To learn which entities Home Assistant includes for a device, area, floor, or label, and how it handles several entities, refer to Automation targets.

Trigger variables

When the trigger reacts, the trigger variable identifies the entity that made it react. This is useful when a target contains multiple entities, such as a device, area, floor, or label.

The following trigger-specific variables are available:

• trigger.entity_id: Entity ID of the entity that made the trigger react.
• trigger.from_state: Previous state object of that entity.
• trigger.to_state: New state object of that entity.
• trigger.for: Timedelta object of how long the trigger criteria were met, if applicable.

For example, use {{ trigger.to_state.name }} in an action to include the name of the entity that made the trigger react in a notification.

The trigger variable describes the entity that made the trigger react. It doesn’t contain all the entities of the target.

Behavior with multiple targets

When you target more than one entity (or select an area, floor, or label that contains several), the Trigger when option controls how the trigger responds:

• Each (default): the trigger fires every time any one of the targeted entities transitions. For example, if you monitor three motion sensors in the living room and someone walks past sensor 1, the automation fires. When they walk past sensor 2 a moment later, it fires again. Every individual event counts.
• First: the trigger fires only on the first transition in the targeted group, then waits until none of the targeted entities is in that state anymore before it fires again. For example, if you monitor the same three motion sensors, the automation fires when the first one picks up movement (someone entered the room). The other two firing afterward are ignored, so you get one notification per “someone walked in” event instead of three.
• All: the trigger fires only after the last targeted entity in the group has fired, meaning all of them are now in the expected state. For example, if you monitor the lights in the living room, bedroom, and hallway, the automation fires only once all three have turned off. This is useful for scenarios like “start the robot vacuum only after every light on the floor is off,” so you know the room is truly empty.

Good to know

• The target climate entity must support the HVAC mode you want to use.
• The available modes depend entirely on the device. Check your climate entity’s documentation or the entity’s attributes to see which modes are supported.
• The trigger only reacts when the thermostat changes to one of the selected modes, not when it changes from a selected mode to a mode that isn’t selected. It also doesn’t react when the thermostat switches between two selected modes. For example, with Heat and Cool selected, switching from Heat to Cool doesn’t make the trigger react.
• The HVAC mode is different from the current HVAC action. The mode is what you set the device to do, while the action is what the device is currently doing, such as heating, cooling, or idle.

Try it yourself

Ready to test this? Go to Settings > Automations & scenes, create a new automation, and add this trigger. Save the automation, and then make the trigger react. For example, change the state of the targeted entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more], turn on a light that the trigger monitors, or change its brightness. To check whether the automation ran, open its traces.

More examples

Real scenarios where this trigger fires in automations and scripts. Copy any example and adapt it to your setup. In the visual editor, select the UI options listed in the example when they are available, or paste the YAML code.

Automation: adjust lights when first thermostat switches to auto mode

When the first thermostat in the bedroom area switches to auto mode and stays in that mode for at least 30 seconds, dim all lights to create a comfortable ambiance for sleep. The delay prevents lights from dimming during accidental mode changes, and firing on the first thermostat avoids multiple light adjustments.

• Trigger: Thermostat mode changed
  • Target: Bedroom area
  • Modes: Auto
  • Trigger when: First
  • For at least: 30 seconds
• Action: Turn on light

alias: "Dim lights on auto mode"
triggers:
  - trigger: climate.hvac_mode_changed
    target:
      area_id: bedroom
    options:
      hvac_mode: "auto"
      behavior: first
      for: "00:00:30"
actions:
  - action: light.turn_on
    target:
      entity_id: light.bedroom_ceiling
    data:
      brightness_pct: 30

Still stuck?

To find out why the trigger didn’t react, make the change that it should react to, and then open the traces of the automation. If the automation didn’t run, there’s usually no trace, but some triggers record a Did not trigger trace. For details, refer to Testing automations. For common problems and their solutions, refer to Troubleshooting automations.

If that doesn’t help, the Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with the trigger you’re using and what you expected to happen, or share on our subreddit /r/homeassistant.

Related triggers

Explore related triggers:

• Thermostat turned on: Triggers when one or more thermostats turn on, regardless of the mode.

• Thermostat turned off: Triggers when one or more thermostats turn off.