Heat pump: Which makes sense? (Viessmann Vitocal 250-A?)

Hello everyone,
I am a fairly new homeowner and am just getting to grips with the topics, so please be patient. ;) Our old Rotex heating system (22 years old) already started to give up in the first winter, we managed to fix it, but it was said that we should slowly think about a new purchase. Now the political situation is turbulent as well, so we would like to apply for funding in December and have a heat pump installed next year. The company that does the maintenance (also very well rated on Google) recommended the Viessmann Vitocal 250-A to us, and it also seems to perform very well in Stiftung Warentest. I am aware of the sale to the Americans, but this is not necessarily a deal breaker (I can manage with Indian customer service in English if necessary).

Key data about the house:
- Built in 2001
- 150m² living space, of which 40 are in the basement (half window) and currently do not need to be heated strongly, supply line later on
- 65m² usable area
- Previous owner's consumption: 15,000 kWh/year
- Underfloor heating in the kitchen, living room, and bathrooms, thermostats in the basement and upper floor

It should be quiet (that’s already suitable) and otherwise should be a sensible long-term investment (so if the higher efficiency compensates for the higher purchase costs, it can cost a bit more).

The only thing that surprises me a bit is that the colleague mentioned 35k-40k€ verbally (without subsidies). On the internet, e.g. at EnBW, the total cost comparison was 17-27k€. We have a slight complexity as we are considering building the system behind the garage, so another hole plus laying cables about 20m through the garage (on the wall, not inside the wall), but that shouldn’t cost 10k. Therefore, my questions:

1. Does the model make sense from your point of view or do you recommend others that I should look at (what are the pros & cons?)
2. Does it make more sense to use smaller companies for installation or one of the big providers (if yes, which ones are good?) [We live near Worms, between Mannheim and Frankfurt]

Best regards

Viessmann is traditionally rather expensive. Large supra-regional companies usually also rely on local subcontractors, and you can get a lucky break or a bad deal, but you don't know beforehand. If you're lucky, the main contractor sets certain guidelines, but these are mostly to their advantage (main thing is warmth, saving costs) rather than yours (efficient operation).

I would rather look for someone local who is available, so not tied to a brand or at least offers several different ones. Then preferably Japanese or Korean. Panasonic is somewhat of a secret tip, but LG or Samsung or Daikin are all actually good. Monoblock, simple software, not too much fuss. The German (European?) systems are all overcomplicated in the control. The development engineers wanted to reinvent the wheel again, but the service technicians and installers don't understand it at all.

And it is best to do the 1st step before the 2nd.

First, it must be checked whether the existing grid connection is sufficiently dimensioned for the additional required rated power of the heat pump. The inspection of the electrical system is carried out by an electrical company registered in the installer directory of the local network operator, which coordinates the necessary measures with the network operator.

First, it must be checked whether the existing network connection is adequately dimensioned for the additionally required rated capacity of the heat pump.

With the small power consumption, this is not an issue in 99.9% of cases.

Thanks for your feedback. I have requested a detailed quote. The 4,000€ also include 1,000€ for additional work in the garage. I think I would spend the 17k for the Viessmann 250 A, but I wonder if all the additional topics are relevant or possibly oversized (e.g. 600L buffer). What do you think? Where can we still save here or is everything reasonable from a long-term business case perspective?

Topics are relevant or possibly oversized (e.g. 600L buffer).

Buffer tanks are almost always unnecessary. Domestic hot water tanks are sufficient - but if the system looks like that because it is specified that way by Viessmann, then you have a tougher nut to crack.