A Home Assistant blueprint for creating alerts if a powered device (like a heater) operates above a certain power threshold for a certain duration.

heater-overrun-notify-blueprint.yaml

blueprint:
  name: Heater overrun
  description: Do something when a heater operates too long.
  domain: automation
  input:
    power_sensor:
      name: Power Sensor
      description: Power sensor entity (e.g. from a smart plug device).
      selector:
        entity:
          domain: sensor
    overrun_threshold:
      name: Starting power threshold
      description: Power threshold above which we assume the heater has started.
      default: 300.0
      selector:
        number:
          min: 10.0
          max: 3000.0
          unit_of_measurement: W
          mode: slider
          step: 10
    overrun_duration:
      name: Overrun duration
      description: Time duration after which we consider the heater is overrunning.
      default: 120
      selector:
        number:
          min: 5.0
          max: 240.0
          unit_of_measurement: min
          mode: slider
          step: 5.0
    actions:
      name: Actions
      description: Actions (e.g. pushing a notification, TTS announcement, ...)
      selector:
        action: {}
  source_url: https://gist.github.com/subpardaemon/ad2be620c76662ff4d977eae77ee9b6a
trigger:
- platform: numeric_state
  entity_id: !input 'power_sensor'
  for:
    minutes: !input 'overrun_duration'
  above: !input 'overrun_threshold'
condition: []
action:
- choose: []
  default: !input 'actions'
mode: single
max_exceeded: silent