What this error means (light template)?

[pedolsky]

You have to set a default value, see here for more info:

Updating Templates with the new default values in 2021.10.x

I keep seeing the same question about the new default argument for the templating. This post will cover all possible ways to define default. All the methods that were changed: acos as_timestamp asin atan atan2 cos float log round sin sqrt strptime tan timestamp_custom timestamp_local timestamp_utc Each of them have the exact same default functionality but a different number of arguments. There are multiple ways to use these functions, and this is where all the confusion lies. Understandi…

Template, 'unknown', default value, and restarts

Thanks for helping Here’s one: - sensor: - name: "boiler_power" unit_of_measurement: 'W' unique_id: "sensor.boiler_power" device_class: power state: "{{ states('sensor.boiler_l1_power') | float(0.0) * 3 }}" state_class: measurement