Recommendation digital heating thermostat

Sure, basically yes. But if in the next few years I have higher consumption with the heat pump than with gas, meaning I pay more for electricity, it might not be worth it anymore. Those are my concerns.

Then just think rationally about what it means for you to have a surplus of €15,000. If you were wasting €500 with gas and (unrealistic) €1,000 with electricity per year, you could easily pay the additional consumption from the surplus of the subsidy for about 30 years. However, CO2 taxes will work against you. And with reasonable planning, the "additional costs" will too, so that you will always be the "loser" with the gas heating.

Now the offer stands to pay about 3000 euros more for the heat pump and thus achieve kfw55. That makes me start to ponder.

I would be very careful here. Because the small surcharge suggests that the same assumptions and the same designs are made for gas and heat pump, and the surcharge is only the pure additional cost for the heat source.

But you cannot transfer it 1:1 and no general contractor will do more and spend more money than necessary. In other words, the heating design will (possibly) be intended for a gas boiler. For 3K more you simply get a heat pump but with the same hydraulics as for gas. From the general contractor’s side everything is okay, the house builder is just supposed to operate a higher flow temperature.

So I would ask very precisely and have the numbers shown to me for what kind of system would come into the house for 3K more.

I would be very careful here. Because the small surcharge suggests that the same assumptions and the same designs for gas and heat pump are made here, and the surcharge is only the pure additional cost for the heat source.

But you can't simply transfer it 1:1 and no general contractor will do more and spend more money than necessary. In other words, the heating system design will (possibly) be intended for a gas boiler. For 3K more, you just get a heat pump but with the same hydraulics as for gas. From the contractor's side, everything is okay; the builder just has to run a higher flow temperature.

So I would ask very carefully and ask to see the figures of what kind of system would come into the house for 3K more.

I have the designations of the devices. What should I pay attention to? According to the company, the system is already designed for the heat pump. How can I tell if that is true? And shouldn't the energy consultant pay attention to that, who should be involved for the KfW55 subsidy?

Well, as of today, my gas will not be more expensive next year; I have already received confirmation for the next renewal.

Please note the reservations in the fine print about changing levies and taxes.
As far as I know, this should already be included, provided the contract start date is already in 2021.

Against your assumptions speaks also the new gas pipeline from Russia.

Wait and see. That thing was expensive and has to be paid for.
The problem with gas or electricity is not that producer prices rise/drop (drastically), but that public levies and taxes change. Mostly in only one direction, and these are politically prefigured significantly for fossil fuels.
We'll see.

The problem with turnkey construction is that you do not choose the heating installer yourself. I also did not want to study in order to decide on a heating system.

Still, this can be clarified beforehand if you know that this is a relevant area that requires a little extra attention alongside window foil applications.

I have the device designations. What do I have to pay attention to?
According to the company, the system is already designed for the heat pump. How can I tell if that is true?
And shouldn't the energy consultant pay attention to that, who should be involved for the Kfw55 subsidy?

You have to ensure that the size of the heat pump matches the heating load calculation (which must be created and not just guessed). An oversized heat pump costs unnecessarily in acquisition and tends to short-cycle in operation. Ideally, it is a modulating device.

If you only want to "prepare" for a heat pump, the most important thing is the close pipe spacing of max. 10cm, preferably less in bathrooms, and the omission of additional radiators.
The entire system should be designed for a maximum supply temperature of 35 °C.

In case of a retrofit, it would also be practical to be able to simply mount the outdoor unit of the heat pump, e.g., by positioning the heating system in the floor plan so that it is located on an exterior wall and this remains or can be made free for an outdoor unit. Electricity can be retrofitted.
The position should also cause as little conflict potential with the neighbor as possible (possible noise exposure).
Alternatively, prepare the heating room so that it is suitable for an indoor heat pump. This means a certain room size and the possibility for supply/exhaust air with a fairly large cross-section. So here again an exterior wall or, in the case of a basement, two shafts should be planned and the noise exposure considered (I have a neighbor here who has both directed onto his own terrace. I am very curious how happy he will be...).

You are making an expenditure here of several hundred thousand euros and have to make decisions that cannot be changed later or can only be corrected at high cost.

I had decided for myself to familiarize myself with the trades of heating/insulation and electrical work at least to the extent that I can avoid the biggest mistakes.

According to the company, the system is already designed for the heat pump. How can I see if that is true?
And shouldn't the energy consultant pay attention to that, who is supposed to be involved for the Kfw55 funding?

The energy consultant is often just a rubber-stamper. I wouldn’t rely on statements from the overall contractor. Only on hard numbers. That means a complete heating load calculation and the planning of the system.