Battery level changed

The Battery level changed trigger fires after a battery level reading changes. Battery levels drain gradually as devices are used, recharge when plugged in, or spike briefly when sensors report a fresh reading. Use the threshold type to filter which changes matter to your automation.

The threshold type controls where the new reading must land for the trigger to fire. You can require the new value to be above a level, below a level, within a range, or outside a range. You can also select Any change to fire on any change at all.

Use Battery level changed to get notified when a device starts running low, log battery drain over time, or trigger a reminder to swap out the batteries in a frequently used sensor.

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 Battery level 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 battery-powered device is in (like your hallway or garden). You can also select a device, a specific entity, or a label. When you target multiple entities (via area, label, or multiple entity selections), the trigger fires whenever any of them changes.
5. From the triggers shown for that target, select Battery level changed.
6. Under Threshold type, configure what kind of change fires the trigger:
   • Select Any change to fire on any change, regardless of direction or new value.
   • Select Above or Below and enter a value to fire only when the new reading is above or below that value.
   • Select In range and enter a lower and upper bound to fire only when the new reading falls inside the range.
   • Select Outside range and enter a lower and upper bound to fire only when the new reading is outside the range.
   • For each option, you can enter a fixed percentage (0–100%), pick a sensor entity, or a number helper entity as the threshold.
     • If you don’t have a number helper, you can create one by selecting Create a new number helper.
7. 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, Battery level changed is referred to as battery.level_changed. A basic example looks like this:

trigger: battery.level_changed
target:
  entity_id: sensor.front_door_sensor_battery
options:
  threshold:
    type: below
    value:
      number: 20

This fires whenever the front door sensor battery drops below 20%.

To fire only when the new reading falls within a healthy charge range after a recharge:

trigger: battery.level_changed
target:
  entity_id:
    - sensor.front_door_sensor_battery
    - sensor.garden_camera_battery
options:
  threshold:
    type: between
    value_min:
      number: 79
    value_max:
      number: 100

This fires whenever either device charges back to 80% or above (up to, but not including, 100%).

To use a number helper as a dynamic threshold you can adjust without editing the automation:

trigger: battery.level_changed
target:
  entity_id: sensor.front_door_sensor_battery
options:
  threshold:
    type: below
    value:
      entity: input_number.low_battery_alert_threshold

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 battery entity behind that target.

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

Good to know

• The threshold type controls both the direction and the landing zone of the change. Use Above or Below to filter by direction, In range to fire only when the new value is inside a range, and Outside range to fire only when it escapes a range.
• Use Any change to fire on every reading update regardless of direction or where the new value lands.
• To react only when a battery level first crosses a specific value, use Battery level crossed threshold instead.
• Pair this trigger with the Battery level condition to verify the reading meets a threshold before continuing the automation.
• The trigger works with sensors that have the battery device class.

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: notify when a door sensor battery is running low

Door sensors sit in corners and rarely get attention until they stop responding. This automation sends a notification whenever the front door sensor battery drops below 25%, so you can replace it before it fails.

• Trigger: Battery level changed
  • Target: Front door sensor battery entity
  • Threshold type: Below 25%
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Notify when front door sensor battery is low"
triggers:
  - trigger: battery.level_changed
    target:
      entity_id: sensor.front_door_sensor_battery
    options:
      threshold:
        type: below
        value:
          number: 25
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      message: "Front door sensor battery is below 25%. Time to replace it."