home-assistant-configuration/config/sensors/power.yaml

# - platform: template
#   sensors:
#     low_battery:
#       friendly_name: 'Low Battery'
#       value_template: >
#         {%- set threshold = 15 -%}
#         {%- set domains = ['light', 'switch', 'sensor', 'zwave', 'lock', 'binary_sensor'] -%}
#         {%- for domain in domains -%}
#           {%- for item in states[domain] if ((item.attributes.battery_level is defined and item.attributes['battery_level'] | int < threshold) or ("battery" in item.name | lower and ((item.state | int < threshold and item.state|int != 0) or item.state | lower == "low" or item.state | lower == "unknown"))) -%}
#             {{ item.attributes.friendly_name }} (
#             {%- if item.attributes.battery_level is defined -%}
#               {{ item.attributes.battery_level}}
#             {%- else -%}
#               {{item.state}}
#             {%- endif -%}%)
#             {%- if not loop.last -%}
#               {{', '}}
#             {%- endif -%}
#           {%- endfor -%}
#         {%- endfor -%}