Heating Oil tank volume

Configuration
1

I am a relative newbee to HA and could do with some help

I have an MQTT sensor measuring aggregated Oil Usage using a meter with a pulsed output

Mqtt sensors

mqtt:
sensor:
- name: “Heating Oil Consumption”
state_topic: “1778385702/TCh1”
unit_of_measurement: ‘l’
value_template: “{{ value | multiply(0.02) | round(2) }}”

This works perfectly

I now wish to subtract this value from the original tank oil volume which was 1600 litres so that I can display the remaining volume as oil is consumed ie. 1600 - (total oil usage)

How can I go about this please ?

2

Firstly, please do this in future: https://community.home-assistant.io/t/how-to-help-us-help-you-or-how-to-ask-a-good-question/114371#oneone-format-it-properly-16

value_template: "{{ 1600 - value | multiply(0.02) | round(2) }}"
3 
# Mqtt sensors
mqtt:
  sensor:
    - name: "Heating Oil Consumption"
      state_topic: "1778385702/TCh1"
      unit_of_measurement: 'l'
      value_template: "{{ value | multiply(0.02) | round(2) }}"

  Thanks
4

Perfect thankyou. Every day is a learning day !