wattage template

template:
  - sensor:
      - unique_id: air_purifier_power_watts
        name: Air Purifier Power Use
        unit_of_measurement: W
        icon: mdi:flash
        state: >
          {% set voltage = states('sensor.air_purifier_voltage')|float %}
          {% set current = states('sensor.air_purifier_current')|float %}
          {% set wattage = (voltage * current) %}
          {{ wattage }}

# Alternatively, the entire state template can be condensed down to:
# {{ ((states('sensor.air_purifier_voltage')|float) * (states('sensor.air_purifier_current')|float)) }}
# But I think it looks nicer and more readable this way.