Thermostats - How to make a more stable heating profile?

Hardware
1

I have a Bosch SMC integration with room thermostat and heater valves.
I turned off the Bosch automations and set it to manual but let HA handle the automation.
The temperature is kept by the Bosch devices.

But my room temperature graph looks like this:

Screenshot 2026-02-17 at 18-35-56 Verlauf – Home Assistant
Screenshot 2026-02-17 at 18-35-56 Verlauf – Home Assistant1077×434 18.8 KB

Is there somewhere that I can fine tune the valve behaviour to keep the temperature more constant?

For the metalevel:
It is a big room approximately 10m x 17m x 3m with 4 large 3m x 1,50m radiators with separate valves.
Do I get any benefits in an efficiency sense if keep the temperature more constant instead of just being less annoying to very temperature sense aware people?

2

To be fair, that’s less than 3 degrees…

You would need to use PID control if you want closer, but would you know there is a ~3 degree swing if you didn’t see the graph?

3

On top of any PID control as stated by SG, you would need to account for the warm up and cool down times of the valves closing and opening to keep a consistent temperature you are targeting for the season.

4

The smarmy marketing text around the Bosch App imply-promises to do exactly that. Self-calibrate this in an external data augmented feedback loop.