Underfloor heating air-water heat pump. House too warm when the sun shines

Turn off circulation then you always have warm water. Hot water at 48 degrees and 6k hysteresis

Phew no, then it heats up to 54 degrees. That is not very efficient. It simply depends on demand (time, amount) and how large the storage tank is.

No, you are thinking wrong

Turn off circulation then you always have warm water. Hot water at 48 degrees and 6k hysteresis

But then you have to run the water for 1 minute first until it gets warm, right? Our experience. Actually, total water waste.

Phew no, then you heat up to 54 degrees. That is not very efficient. It simply depends on demand (time, quantity) and how large the tank is.

We have a 180-liter tank, hot water from 6 am to 7 pm. Circulation permanently on

No, you are thinking wrong

Correct.
48 degrees as the setpoint with a 6K hysteresis causes heating from 45 degrees and ends at 51 degrees.
That should fit.

Really? I had thought heating would continue up to 48° and only start again when it reaches (drops below) 42°. That’s how I understood it so far. How quickly it gets warm without circulation depends on how long the line is from the buffer to the point of withdrawal. I have all hot water draw-off points in the immediate vicinity of the HAR. None should be more than 4m away. That should only take about 10 seconds, I think... It could be different for you, of course.