Air-to-water heat pump consumption at 30 kWh per day

Hello everyone,

we have an air-to-water heat pump from Kermi with 8kW power and a KfW55 house with approx. 200m². Currently, it is also relatively warm with 24.5°C in the house. Yes, yes, I know that is quite high. The consumptions are only for the underfloor heating and separate from the hot water.

I am aware that we have a higher consumption due to the high temperature, but is it possibly too high?

We live slightly north of Hanau and had a temperature of ~23°C in December with a consumption of 6-8kWh per day at times. When it got colder around Christmas, it was about 20kWh. It has now gotten a bit colder again (-6 to 2) and at the same time we set the temperature to ~24°C and now have a consumption of 30kWh.

I had read that average consumptions are based on 19°C and per degree, you need about 10% more energy. So we would be at about 60% more, but are the 30kWh then appropriate? According to the KfW application, we need about 30W/m2, so we come to 6kW, but what is the 6kW related to? 24h? Which outdoor temperature? 19°C indoor temperature?

We had consumption of 6kWh per day in December, which I find quite good, but a few degrees colder and the heating curve raised by 1°C and then such an increase? By the way, we only heat via the heating curve, so without any other controllers.

Thanks in advance :)

According to the KfW application, we need approx. 30W/m2

That is just a number. It has nothing to do with consumption or similar.

What did the room-by-room heating load calculation say? How is the underfloor heating designed? What kind of air-to-water heat pump?
Of course, you have sauna temperatures, that definitely costs a lot of money. Regardless of whether the heating is well or poorly designed.
Such consumption at subzero temperatures can happen...
But we know too little about the heating for that.

Hey, here are the data:

We have two calculations: Kermi (engineer)
Heating load calculation by Kermi: 8475 (6650)
Underfloor heating design Kermi: 20/24 (21/24)

The underfloor heating was installed as closely as possible, with increased density at the windows.

We also have a controlled residential ventilation system (also from Kermi). It runs 24/7 and when I turn it off, the room temperature rises by 1°C.

30kwh per day are absolutely within the limits given the area and temperatures, even rather good!

Although the question is why one needs 24 degrees? In summer I would activate the air conditioning and cool down to 21. Crazy!

At these temperatures and size, the values certainly do not fall outside the norm.

If you had designed the underfloor heating to 24 degrees from the start, it would have been cheaper. 1 degree higher flow temperature already costs about 2 percent efficiency, and then there is the additional consumption. Nevertheless, a thermal balancing should still be carried out.