Template Sensor „cloning“ a water meter

Configuration
1

I want to create a template sensor that basically duplicates my water meter which has two entities: total usage in m3 and current usage in l/min.
The only difference shall be that I want to add an offset to the total usage.
How could I achieve this?
Thank you!

2

For total useage you can create a utility meter helper in the UI. You can then “calibrate” it by setting it to whatever starting value you want with the calibrate service.

This will create a new entity which will get tied to the existing device.

3

Wow, this was exactly what I needed. Thanks for this valuable hint!
I have set it up properly and have created a new graph in Grafana too. But it won’t use m3 as a unit, rather it’s just „state“ that is suggested as unit.

Can I somehow change the unit of the utility meter?

EDIT:
Adding to configuration.yaml the following
:

homeassistant:
  customize:
    sensor.water_meter:
      unit_of_measurement: „m3“
      device_class: water
      state_class: total_increasing

worked so that the unit is showing correct in my dashboard.
However, in Grafana, when I set up a new View for the water meter, the suggested unit is still „state“.
Does this have to do with InfluxDB? Since it wasn’t initially under „m3“?

EDIT 2:
I just have to FIRST define the unit of measurement in the configuration for the sensor and THEN create the utility meter sensor with the same name as in the configuration. Then InfluxDB will put the measurements under „m3“ and Grafana will suggest m3 as unit.

4

The utility meter just takes the measurement unit of the source sensor, so make sure the original sensor has the correct units before creating the utility meter.

Also, if you want to integrate it into the energy dashboard, you’ll have to make sure it is in one of the supported untits. For cubic meters, it must be specified with the superscript 3: m³

5

That’s weird, the source sensor‘s unit is definetly cubic meters. The utility meter‘s unit however was „state“ when I first created it. It was only when I added the Customize part to my configuration before creating the utility meter that it would be m3.
I can see it in the energy dashboard too.

Unfortunately I can’t test anything really, since I’m not at home until Saturday auto turn on the water.