History graphs for helper entities are drawn separately from regular entities of the same unit

[neuviemeporte]

Checklist

• I have updated to the latest available Home Assistant version.
• I have cleared the cache of my browser.
• I have tried a different browser to see if it is related to my browser.
• I have tried reproducing the issue in safe mode to rule out problems with unsupported custom resources.

Describe the issue you are experiencing

I have a bunch of temperature sensors around the house. I also created some helper entities from the temperature sensors, e.g. an entity calculating the average of a group of "real" sensors. I also have a custom dashboard for temperature and heating with history graph cards for the temperatures. In the cards on the dashboard, the temperature sensors are combined into one graph as expected.

However, when I click on the card to go into the detailed history view, the derived helper ("Temperatura średnia piętro") entity is drawn on a separate graph, which makes it difficult to cross reference with the rest of the history.

Describe the behavior you expected

I would expect the helper entity to be on the same graph as the rest of the entities with the same unit (deg C).

Steps to reproduce the issue

1.Install some temperature sensors (mine are z2m, but had the same problem with zha in the past)
2.Go into helpers, create helper->Combine the state of several sensors, select sensors to derive the value from, type e.g. arithmetic mean
3.Go into history view, pick a "real" temperature sensor. Then, pick the helper. Both are in deg C, but two separate plots are shown

What version of Home Assistant Core has the issue?

2025.5.1

What was the last working version of Home Assistant Core?

No response

In which browser are you experiencing the issue?

Firefox 143.0.4 (64-bit

Which operating system are you using to run this browser?

Windows 10

State of relevant entities

"normal" sensor:
state_class: measurement
unit_of_measurement: °C
device_class: temperature
friendly_name: Temperatura u Ani

average temp helper:
state_class: measurement
unit_of_measurement: °C
icon: mdi:thermometer
friendly_name: Temperatura średnia piętro

Problem-relevant frontend configuration

JavaScript errors shown in your browser console/inspector

Additional information

No response

[karwosts]

They are separated as they are a different device class. Does the combine state give the option of setting a device class?

[neuviemeporte]

Unfortunately not: https://www.home-assistant.io/integrations/min_max

It seems like it would be a good idea for the helper to inherit the device class of the entities it's combining?

In addition to the graph problem, I also can't use the average temperature helper as a temperature sensor for my thermostat, presumably for the same reason.