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 can optionally filter the trigger to fire only when the thermostat switches to one or more specific modes. Leave the mode option empty to fire on any mode change.

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. Optionally, under Modes, select one or more modes you want to watch for. Leave it empty to trigger on any mode change.
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.

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

This fires every time the HVAC mode of climate.living_room changes to any mode.

To fire only when the thermostat switches to a specific mode:

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

Options in YAML

YAML sometimes provides additional options for more complex use cases that are not available through the UI.

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.

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 (any in YAML, 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 (first in YAML): the trigger fires only on the first transition in the targeted group, then waits until all targeted entities have reset 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 (last in YAML): 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 available modes depend entirely on the device. Check your climate entity’s documentation or the entity’s attributes to see which modes are supported.
• If you filter by mode, the trigger only fires when the device enters that mode, not when it leaves it.
• The HVAC mode is different from the hvac_action. The mode is what you set the device to do, while the action is what the device is currently doing (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, then change the state of the targeted entity to watch the trigger fire on your actual entitiesAn 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].

More examples

Real scenarios where this trigger fires in automations and scripts. Copy any example and adapt it to your setup.

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?

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

These triggers work well alongside this one:

• Thermostat turned on: Triggers after one or more climate devices turn on, regardless of the mode.

• Thermostat turned off: Triggers after one or more climate devices turn off.