Air heat pump or use gas and solar?

Why does the hot water preparation rely on the heating element? With our air-to-water heat pump, the heating element did not even turn on during hot water preparation at -5 degrees. With a brine-to-water heat pump, the source temperature is significantly higher, so why should the heating element activate there? The temperature of the source is not adopted 1:1 there either.

So the "very experienced" may be true, but then "not trained" probably applies as well. Because the installer's statement is simply completely wrong. Apparently, he has never glanced at the manual of any heat pump in his entire life. A pity for a professional.
As evidence, I have put the technical data from a brine heat pump manual (~4 years old, a model similar to mine) into a picture. I'm sure if you look at a current heat pump of your choice, you will surely find even better data by now. What can you read from it?
Up to a brine temperature of 0° at the input, the heat pump heats water up to 60° with a performance factor of 2.4, i.e. from 1kWh of electricity → about 2.4kWh of heat energy, and if you save a bit and only operate with a 55° warm storage, you can run with even colder brine or get better performance factors (my borehole has always remained in the positive range as input, even in winter rather +5 to +10°, but for the devices it is basically completely normal to work with negative brine temperatures, this is often the case with trench collectors → the icing provides a lot of energy).
My brine heat pump has not once gone into heating rod operation in the last 4 years. It can be as cold as it wants outside, the brine temperature was stable and the efficiencies good (at 0° brine, the heat pump is sufficient for us down to about -30°C outside temperature in terms of output).
So I can only agree with the previous speaker. Especially when it is very cold, the brine heat pump is advantageous compared to an air-water heat pump.

[Edit] The performance factors don't look that impressive yet, but at 0° outside temperature we have a flow temperature of about 25°, and at a brine temperature between 5 and 10 degrees you are already in the upper 6 range...

Why does the hot water preparation switch to the heating element? With our air-water heat pump, the heating element did not turn on during hot water preparation even at -5 degrees.

It was not about the outside temperature; he said the heat pump can only heat the hot water up to 25° with geothermal energy and then the heating element kicks in. I need to look for the manual of the Waterkotte AI 1 Geo and read up on it. Although I always worry that the manufacturers give overly optimistic phantom values (see emissions scandal, etc.).


It is really a huge problem to find someone who can solve the puzzle.

It was not about the outside temperature; he said the heat pump can only heat the water to 25° using geothermal energy and then the heating element kicks in.

That sounds like nonsense. A heat pump always works with a compressor etc. to raise temperatures; in an air-to-water heat pump, it naturally has more to do than in a ground-to-water heat pump, which is why it consumes more energy. This has nothing to do with the heating element, which is only there for emergencies. You can easily Google that in 2 minutes. I wouldn’t put any stock in this "expert’s" opinion.

Is it possible to find out specifically for this heat pump how efficient it is for hot water preparation?

I cannot find a user manual. Does the heat pump consumption database help in any way? Unfortunately, I don't see anything there that I could extract.

Do you have such high demands on hot water preparation? With us, with 2 people and an air-to-water heat pump, it was just 50kWh in December.