Attempt at overriding negative values with 0 is not working, but why?

Configuration
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1

Hi, I am about two weeks into my Home Assistant setup, and I've run into a challenge trying to define a template sensor that overrides negative values with zero.

I have a hacked Curb device that uses ha-energycurb to incorporate circuit-level power consumption into HA. But it can't measure every circuit. So to get "other" consumption, I created a template sensor for "other" so that all individual circuits + "other" add up to total household consumption.

That's easy enough, except that sometimes due to either timing mismatches in sensor readings or inevitable inaccuracy in the CT current measurements, I'm ending up with negative "other" consumption values that I'd like to override with 0 to avoid confusion in charts and automation logic.

I've tried two different approaches that I found mentioned on this forum in various topics, but neither is working for me. (I'm ending up with "other" being "NA" in charts and "unavailable" in the entity configuration view with both approaches, so I'm fairly sure it's not basic syntax issues, e.g. bad indentation, etc.)

I expected one of these to work. Can anyone help me out with a solution?

(Try #1) Using if-then logic:

    - name: curb_other_power
      state: >
        {{
          iif(
            states('sensor.curb_total_consumption_power' | float)  - states('curb_all_circuits_power' | float)  < 0,
            0,
            states('sensor.curb_total_consumption_power' | float)  - states('curb_all_circuits_power' | float) 
          )
        }}
      device_class: "power"
      unit_of_measurement: 'W'

(Try #2) Using a clever python trick to sort and take the second value:

    - name: curb_other_power
      state: >-
        {% set total_cons = (states('sensor.curb_total_consumption_power') | float) | round | int %}
        {% set all_circuits = (states('sensor.curb_all_circuits_power') | float) | round | int %}
        {% set other = (total_cons - all_circuits) | int %}
        {{ ([0, other] |sort) [1] }}
      device_class: "power"
      unit_of_measurement: 'W'
2

A couple places in Try #1 are missing a ), so it is failing when it tries to set the string sensor.curb_total_consumption_power to a float and has no default to handle non-numeric strings.

Try #2's floats also have no defaults, and for some reason you have stacked multiple number-based filters on top of each other... none of which have defaults.

In both cases you have failed to provide an availability template.

Sensors with defined unit_of_measurement must return a numeric state, you haven't made sure it does. Either provide defaults, add an availability, or both.

    - name: curb_other_power
      state: >-
        {% set total_cons = states('sensor.curb_total_consumption_power') | float %}
        {% set all_circuits = states('sensor.curb_all_circuits_power') | float %}
        {% set other = (total_cons - all_circuits) | int %}
        {{ [0, other] | max }}
      device_class: "power"
      unit_of_measurement: 'W'
      availability: |
        {{ has_value('sensor.curb_total_consumption_power') and has_value('sensor.curb_all_circuits_power') }}
3

You could define a helper using Max(0,val) - the maximum of your sensor and zero is the sensor when more than zero, or zero

4

You were absolutely right about parenthesis and lack of defaults.

This is what is finally looks like when it's correct:

    # OTHER
    - name: curb_other_power
      state: >-
        {% set total_cons = (states('sensor.curb_total_consumption_power') | float(0)) %}
        {% set all_circuits = (states('sensor.curb_all_circuits_power') | float(0)) %}
        {% set other = (total_cons - all_circuits) %}
        {{ ([0, other] |sort) [1] }}
      state_class: measurement
      device_class: "power"
      unit_of_measurement: 'W'
      availability: |
        {{ has_value('sensor.curb_total_consumption_power') and has_value('sensor.curb_all_circuits_power') }}

This is what I get for learning just looking at code examples instead of actually reading documentation.