Battery level crossed threshold

The Battery level crossed threshold trigger fires when a battery level crosses into a zone you define. A smoke detector crossing below 15% after weeks of use, a robot vacuum crossing above 80% after returning to its dock, a reading entering a healthy charge range, or a reading escaping a safe zone are all supported.

Use Battery level crossed threshold to automate alerts when critical devices lose power, confirm when devices finish charging, or pause automations until battery-powered sensors have enough charge to be reliable.

When you target more than one entity, the trigger’s Trigger when option controls when it fires.

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 crossed threshold 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 living room or garden). You can also select a device, a specific entity, or a label.
5. From the triggers shown for that target, select Battery level crossed threshold.
6. Under Threshold type, configure the zone the reading must enter for the trigger to fire:
   • Select Above or Below and enter a value to fire when the reading crosses that level.
   • Select In range and enter a lower and upper bound to fire when the reading enters the range from outside.
   • Select Outside range and enter a lower and upper bound to fire when the reading leaves the range (crosses past either bound).
   • 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. Under Trigger when (see Behavior), pick Each, First, or All to control how the trigger behaves when multiple entities are targeted.
8. Under For at least, set how long the reading must stay past the threshold 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, Battery level crossed threshold is referred to as battery.level_crossed. A basic example looks like this:

trigger: battery.level_crossed
target:
  entity_id: sensor.hallway_motion_sensor_battery
options:
  threshold:
    type: below
    value:
      number: 15

This fires whenever the hallway motion sensor battery crosses below 15%.

To fire when a device charges back into a safe range:

trigger: battery.level_crossed
target:
  entity_id:
    - sensor.hallway_motion_sensor_battery
    - sensor.bedroom_smoke_detector_battery
options:
  threshold:
    type: between
    value_min:
      number: 20
    value_max:
      number: 99
  behavior: last

This fires once both sensors have charged back into the 20–99% range (effective zone: 21%–98%, because between is exclusive on both bounds).

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

trigger: battery.level_crossed
target:
  label_id: critical_sensors
options:
  threshold:
    type: above
    value:
      entity: input_number.battery_replacement_threshold
  behavior: first

This fires when the first sensor with the critical_sensors label crosses above the number helper’s threshold value.

Options in YAML

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

threshold:
  type: below
  value:
    number: 20

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.

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

• Above and Below fire on the crossing moment only. Once the reading is above the threshold, the trigger does not fire again until the reading dips back below it and then crosses above again.
• In range (between) fires when the reading moves from outside the bounds into the bounds. Outside range (outside) fires when the reading moves from inside the bounds past either bound.
• Pair this trigger with the Battery level changed trigger if you also want to react to smaller fluctuations between crossings.
• Pair this trigger with the Battery level condition to double-check the final state.
• 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: send a critical alert when a smoke detector battery runs low

Smoke detector batteries failing silently is a safety risk. This automation sends a notification the moment any smoke detector in the house crosses below 15%, giving you time to replace it before it matters most.

• Trigger: Battery level crossed threshold
  • Target: All smoke detector entities (by label)
  • Threshold type: Below 15%
  • Trigger when: Each
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Alert when smoke detector battery is critical"
triggers:
  - trigger: battery.level_crossed
    target:
      label_id: smoke_detectors
    options:
      threshold:
        type: below
        value:
          number: 15
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      message: "A smoke detector battery is below 15%. Replace it immediately."

Automation: confirm when the robot vacuum is fully charged

The robot vacuum takes a while to charge. This automation sends a notification after the vacuum has stayed above 95% for at least 10 minutes, so you know it’s truly ready and not just briefly peaking.

• Trigger: Battery level crossed threshold
  • Target: Robot vacuum battery entity
  • Threshold type: Above 95%
  • Trigger when: Each
  • For at least: 00:10:00
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Notify when robot vacuum is fully charged"
triggers:
  - trigger: battery.level_crossed
    target:
      entity_id: sensor.robot_vacuum_battery
    options:
      threshold:
        type: above
        value:
          number: 95
      for: "00:10:00"
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      message: "The robot vacuum is fully charged and ready to go."

Automation: alert when adjustable threshold is crossed

Use a number helper so you can change the alert threshold from the UI without editing the automation.

• Trigger: Battery level crossed threshold
  • Target: Garden camera battery entity
  • Threshold type: Below (entity: low battery threshold helper)
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Garden camera low battery alert"
triggers:
  - trigger: battery.level_crossed
    target:
      entity_id: sensor.garden_camera_battery
    options:
      threshold:
        type: below
        value:
          entity: input_number.low_battery_alert_threshold
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      message: "Garden camera battery is below the configured alert level."