Why don't construction prices go down?

What outdoor temperature (AT) have you had in the last few days?
What room temperature (RT) do you have?
Are all rooms comfortably warm? Maybe some warmer than desired?
How is the heating curve? How is the flow temperature?

Depending on the AT, there is no average. And at the beginning, there is always more construction moisture in the house; the heating energy demand is still higher in the first year than later.

AT between +5 and -3 degrees
RT approx. 25/26 degrees (not measured) thermostats almost fully turned up everywhere
Heating curve 0.5, flow temperature 31.5 degrees
According to the energy certificate, I calculated with much less. Sure, now it is winter, but if this stays like this for 3-4 months, it means electricity costs of 400 euros per month (!) Something must be wrong here.

Edit: just now while watching TV the thermostat clicks every 10 minutes, is that normal?

The thermostat is crap. Please measure RT (there are very cheap thermometers, just distribute a few of them around the house). If 25-26°C is correct (which can certainly be the case with a flow temperature of 31.5°C), then you have to realize that this is about 4-6°C warmer than "normal". The DIN standard specifies 20°C for living rooms and 24°C for bathrooms. It is often common in modern new buildings to aim for 21-22°C, but 25°C is already really cozy warm and usually more typical for houses with fireplaces. The heating curve of 0.5 is also way too high for a new building. I have a KfW-70 house and operate with a heating curve of 0.15. However, even then I cannot reach my set WT (but I control differently). Try at least to lower the WT to 23°C and the heating curve to at least 0.2. Then wait two days. If it becomes too cold somewhere, you either have to raise WT again or set a steeper curve. There are different philosophies for this. Google hydraulic and thermal balancing...

It could be, we consumed 210 kWh in the last 5 days. Half of that from the heat pump.

So about 20 kWh/day with the heat pump is about right? That's what my "new" existing property has been using recently at 0 to -2°C, I was a bit puzzled whether that's normal. But it seems to be the case. Thanks for the figures :)

So about 20 kWh/day with a heat pump sounds about right? That’s what my "new" existing property has needed recently at 0 to -2°C, I was a bit confused whether that’s normal. But it seems to be so. Thanks for the numbers :)

You can’t really say that in general terms, we have now had 2 new buildings with heat pumps, and the consumption is very different. The first was located in Lower Saxony and was a Frisian house, so with sloping roofs in the upper floor. This one is in the Southwest Palatinate, is half built into a hillside (so has earth contact on some walls), and we don’t have any sloping roofs, but high ceilings instead, and over 100 m² more heated area. Here there is simply significantly more air in the house that needs to be heated. You can notice that very much in the consumption, of course. That was yesterday. But that is the total consumption, including car charging and birthday party with cake baking, etc. =D

So in 4.5 days we have consumed 160 kWh. That seems extremely high to me. Can that be right in winter?

Why are you whining? You heat electrically, you drive an electric car and consume 40 kWh per day. And yes, it is winter.
Here I have 30 cm of snow and minus 6 degrees. What will you do when climate change fails and it’s minus 20 degrees? Then your heating will need twice as much again. Energy calculators tend to make everything look good.

20 degrees in living rooms? Is that the Habeck comfort temperature in a newly built house? That would be too cold for me.
40 kWh hours, of which 10 kWh are certainly normal household electricity, is not much. That would be 4 liters of heating oil. Where is the problem?
I would rather say, that is still a cheap consumption.

Otherwise, we currently still have the electricity price brake. 40 cents per kWh. Or you emigrate to Austria. There the price brake is 10 cents.
Well, yes, they also earn more.