Power consumption of a heat pump

We have a groundwater heat pump, a heating rod for hot water and a ....

- the esteemed boxwood is not entirely wrong, the hot water is (for whatever reason) generated by the heating rod - so it is probably stored in the hot water tank, possibly with the legionella program regularly carried out. - not all experts here in the forum master coffee grounds reading, so you do have to provide a little meat on the bones in the form of data

My smart meter shows exactly the same peak at 0400 every night; I assume this is due to the heating curve; looking forward to the [Sanitär] response

I still suspect hot water. Have you checked if a timer program is set for it?

Hot water is heated by the heat pump up to 40 °C and further heated to 55 °C with the heating rod. These are the small peaks in the curves, but never more than one hour without a break. The heating rod is controlled exclusively by the thermostat; there is no time program. The unusual power consumption around 04:00 appeared for the first time on 01.10.2023 and then every day. It cannot be related to the outside temperature, as it was not exactly the same every day. It remains a mystery!

I cannot regularly identify any extraordinary spikes at four in the morning from the presented diagrams. The consumption appears to come from the compressor starts, spread over the day. The one peak at quarter past four is probably the activation of the heating element, by the way, like at other times as well. where do you see the puzzle?
My question is: does the hot water have to be heated to 55°? Wouldn't 40-45° also suffice? Because for the legionella program, 55° is anyway too low, but 40-45° would be manageable for the heat pump without using the heating element.

Why should the heating element always turn on at the same time at night if no hot water is being used?

This can simply be related to the threshold temperature being undershot. If you have a reasonably consistent daily routine every day, it is likely that the temperature (either heating or hot water storage) will also drop below the threshold at a similar time. Alternatively, it could also be a night setback setting, although the time would be strange in that case, but not impossible. Are you sure you have checked all the relevant control options? Sometimes manufacturers hide such settings in a third nested submenu somewhere you would never intuitively expect.