Set fan speed based on sensor value

Configuration
,
1

Hello :wave:

So I am setting a fan based on a CO2 reading- to do this I convert the CO2 reading to a percentage using a template sensor:

template:
  - sensor:
      - name: "Cave Vent Setpoint"
        state: >
           {{ min(max((states('sensor.cave_co2')|float - 600 )/4, 0), 100) }}

The idea here is that the fan goes on at a sensor reading of 600 and maxes out at a reading of 1000.

Then to set the fan speed I have an automation which triggers on every setpoint change:

alias: Auto Cave Speed
description: ""
trigger:
  - platform: state
    entity_id:
      - sensor.cave_vent_setpoint
condition: []
action:
  - service: fan.set_percentage
    data:
      percentage: |
        {{ states('sensor.cave_vent_setpoint') }}
    target:
      entity_id: fan.cave_vent
mode: single

My question is this: Is this the most efficient way of doing this? I was expecting to not have to have the automation trigger all the time by having the template call the set_fan_percentage service, but I couldn’t find a way of calling a service from within a template. Now obviously I could slow it down a bit by not having it trigger all the time, but was hoping for a more elegant solution.