Power changed

The Power changed trigger fires when a power reading changes and the new value matches the threshold you set. You can react to any change, only when the new reading is above or below a limit, or only when it lands inside or outside a range.

Use Power changed when you want to react to the latest power reading right away, such as noticing when an appliance starts drawing noticeable power or when a circuit moves outside its normal operating range.

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 Power 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 power sensor is in. You can also select a device, a specific entity, or a label.
5. From the triggers shown for that target, select Power changed.
6. Under Threshold type, configure what kind of change fires the trigger:
   • Select Any change to fire on any power change.
   • 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 falls outside the range.
   • For each option, you can enter a fixed power value, pick a sensor or number entity, or pick a user-created number helper as the threshold.
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, Power changed is referred to as power.changed. A basic example looks like this:

trigger: power.changed
target:
  entity_id: sensor.washing_machine_power
options:
  threshold:
    type: above
    value:
      number: 10
      unit_of_measurement: "W"

This fires whenever the washing machine power reading changes to a value above 10 W. To fire on any change regardless of direction or value, use type: any and omit value.

To fire only when the new reading lands inside a normal operating range:

trigger: power.changed
target:
  entity_id: sensor.server_rack_power
options:
  threshold:
    type: between
    value_min:
      number: 150
      unit_of_measurement: "W"
    value_max:
      number: 350
      unit_of_measurement: "W"

This fires whenever the server rack power reading changes to a value between 150 W and 350 W.

To use a user-created helperA helper is a virtual entity you create inside Home Assistant. It is not backed by a physical device. Helpers store values, track state, or do calculations that your automations and dashboards need. [Learn more] as a dynamic threshold that you can adjust without editing the automation:

trigger: power.changed
target:
  entity_id: sensor.oven_power
options:
  threshold:
    type: above
    value:
      entity: input_number.high_power_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 power entity behind that target.

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

• Use Power changed when you want to react to the latest reading after it changes. If you need to react only when a reading crosses into or out of a threshold zone, use Power crossed threshold instead.
• Supported thresholds can use fixed values, a sensor with the power device class, a number entity with the power device class, or a user-created helperA helper is a virtual entity you create inside Home Assistant. It is not backed by a physical device. Helpers store values, track state, or do calculations that your automations and dashboards need. [Learn more] from the Input number integration.
• Supported power units are mW, W, kW, MW, GW, TW, and BTU/h.
• If a targeted entity is unknown or unavailable, it cannot fire the trigger until it reports a valid power value again.
• This trigger works with sensors that have the power 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: turn on a status light when the dryer starts drawing power

When the dryer power changes to a value above 20 W, turn on a status light so you can see that a cycle is running.

• Trigger: Power changed
  • Target: Dryer power sensor
  • Threshold type: Above 20 W
• Action: Turn on light
  • Target: light.utility_room_status

alias: "Turn on dryer status light when a cycle starts"
triggers:
  - trigger: power.changed
    target:
      entity_id: sensor.dryer_power
    options:
      threshold:
        type: above
        value:
          number: 20
          unit_of_measurement: "W"
actions:
  - action: light.turn_on
    target:
      entity_id: light.utility_room_status

Automation: send a notification when a server rack leaves its normal power range

When the server rack power changes to a value outside 150 W to 350 W, send a notification so you can check whether something unexpected is happening.

• Trigger: Power changed
  • Target: Server rack power sensor
  • Threshold type: Outside range (150-350 W)
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Alert when server rack power leaves its normal range"
triggers:
  - trigger: power.changed
    target:
      entity_id: sensor.server_rack_power
    options:
      threshold:
        type: outside
        value_min:
          number: 150
          unit_of_measurement: "W"
        value_max:
          number: 350
          unit_of_measurement: "W"
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      message: "Server rack power moved outside its normal range."

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:

• Power crossed threshold: Triggers after one or more power values cross a threshold.