Add L/s (litres per second) as a valid unit of measurement to volume_flow_rate device class

[bradkeifer]

The volume_flow_rate device class currently does not support a litres persecond unit of measurement.

I have a requirement for a sensor and also dashboard display of volume flow rates in litres per second (L/s). I also note that the SI unit of measurement for volume flow rate is cubic metres per second and this is also not supported. I make use of the modbus integration to obtain my sensor data, and I was alerted to the lack of support for the L/s unit of measurement when reviewing the home-assistant.log file at startup, where the following warning message was given:

2024-02-21 10:32:19.879 WARNING (MainThread) [homeassistant.components.sensor] Entity sensor.d1_flow (<class 'homeassistant.components.modbus.sensor.ModbusRegisterSensor'>) is using native unit of measurement 'l/s' which is not a valid unit for the device class ('volume_flow_rate') it is using; expected one of ['m³/h', 'gal/min', 'L/min', 'ft³/min']; Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+modbus%22

The configuration I have for this sensor is:

- name: D1 Flow
        unit_of_measurement: "l/s"
        device_class: volume_flow_rate
        address: 29689
        scale: 1
        precision: 0
        data_type: uint32

I would like to see litres per second (L/s) and possibly cubic metres per second (m³/s) added to the set of units_of_measurement for the volume_flow_rate device class please.

[MartinHjelmare]

Sounds ok to add support for litre per second.

Cubic meter per second doesn't sound like it would be used in a home.

[patrickvorgers]

For residential usage L/h is much more common than m3/h. In my case I have a heatpump which shows the flowrate in L/h.
Has there been an architectural decision whether L/h and/or L/s will be supported?

[mib1185]

the pegel_online integration would benefit from m³/s - see home-assistant/core#143563 (comment)

[mib1185]

@MartinHjelmare would you agree with adding l/s , l/h and m³/s ?

[MartinHjelmare]

Yes, all three are ok add. We're now accepting new units where there's a simple conversion for existing device classes without architecture discussion.

[mib1185]

home-assistant/core#143625