---
- platform: template
  sensors:
    number_light_on:
      friendly_name: "Lights ON"
      unit_of_measurement: light(s)
      value_template: >
        {{ states.light | rejectattr('attributes.color_mode', '==', 'onoff') | rejectattr('attributes.entity_id', 'defined') | selectattr('state', '==', 'on') | map(attribute='entity_id') | list | count }}