Our planning for the home. Entrepreneur wanted

After a long break, a message again
We are now waiting for the last offer, from which we expect the most
It is a revised offer from the provider who already submitted the first offer to us. It is the floor plan posted here. We have slightly revised the floor plan to enlarge the kitchen. We also had a conversation with the general contractor, his heating engineer, and a sales representative from Stiebel Eltron. We want an air-to-water heat pump with a ventilation system with heat recovery. The system will still be calculated by Stiebel based on the floor plan and included in the offer.
We already had a financing consultation shortly before Christmas. Frightening amount, but according to our advisor, no problem, even if one salary fails.
So we are now approaching the decision on whom the contract will be awarded to, then a precise financing plan will be made based on the existing offer, and then it can start soon

So, the final offer is in our hands. The extension and the ventilation system are included, including underfloor heating in 2 of the 3 basement rooms. The offer looks very good! There is only one point that makes us hesitate. The offer includes an air-to-water heat pump from the manufacturer Nibe and a separate ventilation system, also from Nibe. (I have not yet asked which models) But it is a device with a component in the utility room and a component for outdoor installation (for the air-to-water heat pump). For an additional 4,000€, we could get a combined unit from Stiebel Eltron (LWZ 304 SOL) for indoor installation only, with a 700l buffer tank, instead of the two Nibe components. Personally, I would tend to go for Stiebel Eltron – despite the surcharge – because of the name... (Nibe means nothing to me at first) Is there anyone among you who would advise me on a variant?

We are getting a split unit from IDM in Austria. We decided against an indoor unit because of the space. Nibe comes from Scandinavia, I believe from Sweden. My sister has a geothermal heat pump from Nibe and has been very satisfied so far. Nibe has not been a no-name product for a long time. However, I cannot recommend any to you. I think the heating installer knows best.

Two neighbors have devices from Stiebel Eltron: 1.) LWZ 403 SOL ==> very satisfied after one year, low power consumption (in KFW 55 prefabricated house) 2.) LWZ 303 ==> not satisfied after 5 months, as power consumption is 20-40% higher than in 1.) and in a nearly identical house Both heating systems installed by the same installer, 2.) even has almost one degree colder inside the house. Noise level low, ventilation system reduces humidity to 30% in the (warm) winter

Thank you very much for your answers!

Two neighbors have devices from Stiebel Eltron:
1.) LWZ 403 SOL ==> very satisfied after one year, low power consumption (in a KfW 55 prefabricated house)
2.) LWZ 303 ==> not satisfied after 5 months, because power consumption is 20-40% higher than with 1.) and a nearly identical house
Both heating systems installed by the same installer, 2.) even has almost one degree cooler inside the house.
Noise level low, ventilation system reduces humidity in the (warm) winter to 30%

I am not particularly familiar with the subject either, but is it maybe that system 2.) is undersized for the house?

Hello,

I am not particularly familiar with the topic either, but could it be that system 2.) is too small for the house?

Yes.

Rhine greetings