New construction - How to build economically sensibly?

That's not quite true, otherwise I wouldn't have had a KFW 55 house with a heat pump offered to me. The question here is only how it looks in reality or if it's like the "diesel scandal" where car manufacturers determine and specify consumption and emission values that do not correspond to real conditions.

Air heat pumps are probably nonsense in cold regions as they are prone to failure.

We also have one and so do the neighboring houses. It's rather mild here, then suddenly a harsh winter came and 4 air heat pumps broke down. 2 were replaced.

And now? Was it the manufacturer, the general contractor, or Mother Hulda???

Oh no, it was Merkel.

You ask strange questions that no one can answer you.

Back then, no one wanted to believe me about the construction costs.

We started building in mid-2015 and moved in April 2016.
Construction site: Rheinland... rural area between Aachen and Cologne
Whether this is standard now or not, everyone can decide for themselves, but here is a small excerpt of our equipment:
140 sqm living space
masonry 4x9m garage with access to the house
house and garage fully faced with bricks
air-to-water heat pump with integrated ventilation system with heat recovery
kfw 70 according to 2015 standard (corresponds to today's Energy Saving Ordinance standard)
electric shutters
glazed clay tiles
built with an architect and individual trade contracting with companies from the region

Total costs including all ancillary construction costs (without land): €245,000 completely ready to move in
This also included materials for painting work and floors, which we then carried out ourselves.

The problem with a calculation are the parameters you assume. Please determine for your house: expected gas consumption (I calculate 8000 kWh for 110 sqm). Determine the annual price with a usual provider, eon or similar. Determine the electricity consumption. You can transfer the current one to the new house. Determine the additional cost for the heat pump. Determine the one-time costs for the gas connection. Spread them over 15 years. Determine the expected electricity consumption of your new building with the pump; gas will then no longer be needed. Make one table. It should only cover 15 years. Everything else is nonsense, because the heating system, whichever one, will be broken by then anyway. Now calculate. Forecast: a heat pump will only be worthwhile if you assume strongly rising gas prices and moderately rising electricity prices. In my opinion, that is not realistic. Both will rise: gas because of scarcity, electricity because of electric cars. The controlled residential ventilation is, in my opinion, more of a comfort extra than something that saves energy. Photovoltaic system on the roof to support the pump: In my opinion, that won’t make a difference either; the system is simply too expensive in initial investment. My conclusion: if you have money left over, don’t buy home technology but rather a nice garden fountain or something. You’ll enjoy it more. One more thing: if you take KfW funds, there must be proof whether you have reached KfW standards. If you build to the energy saving ordinance basic, you save blower door tests and such. My opinion: the whole current energy saving ordinance is a green-ideological educational concept to promote certain industries under the label of CO2 saving. Nobody calculates what all these things require in CO2 for production, etc. If you really want to save CO2, take the train, walk, buy a gasoline car with 75 hp and a hybrid as well, give up the wood stove, and above all, don’t eat so much meat anymore; then no more rainforest will have to fall for soy plantations. Karsten

200,000€ basic equipment!

You can't just say what basic equipment is like that. Our house provider offered our house back then for 149,000. The result was a house price of 195,000 without upgrades by electricians, plumbers, and tilers. How come? Underfloor heating, controlled ventilation, etc., were not included in the price. For some others here, this is a no-go if a house provider hasn't even priced in shutters and underfloor heating, but offers them as optional upgrades. In this respect, I know that there are indeed houses under 200,000, but I doubt whether you can manage with that sum when you really think about it and want one or the other feature. If you want to avoid polystyrene and build more ecologically, you tend to end up with a provider who is positioned in the higher segment. They then also install more expensive heating technology, possibly also the ventilation system that in my opinion is important. This can easily cost over 12,000. Homeowners who can only build cheaply inevitably choose a builder who omits one or the other thing in the basic equipment, but then you have to live with the fact that it is "only" polystyrene or only gas heating. Everything else in terms of technology then has to be affordable for you. I hope I have made myself clear. On average, calculate 180,000€/sqm plus additional construction costs; with cheaper construction, it can be less, but sooner or later you end up with cheap construction (see [Bauleistungsbeschreibung!!!]), the higher the quality of the [Bauleistungsbeschreibung], the more expensive it can get. Yes, and then there is also the north/south gradient. Down south, it gets more expensive.

Can you say again how much you can/want to spend to be able to live in the finished house including compensation for all additional costs/extra wishes?

No one calculates "just construction" and then sets a budget based on that. Your questions cannot be answered like this.

If your budget has to cover everything as I described above, your questions don’t even arise, as kaho674 explained clearly and correctly: Then you take what you get, because you have no choice anyway.

What is economical in terms of energy supply depends on the outcome of our bets on the future. Personally, I would never want to be dependent on gas; others see it quite differently. I would produce electricity myself via solar and use it myself until the last bit before feeding any into the grid – financially nonsensical, ecologically sensible. Future-proof, in my personal opinion. Others see it exactly the opposite.

How are your questions supposed to be answered under these conditions? The "economy" of a house build is highly subjective.

The only objective truth, namely that a newly built single-family house is per se uneconomical (in every respect), is the only fact and at the same time also the only thing a builder must disregard, otherwise one would not be a builder.

200,000€ basic equipment
!

You can't say what basic equipment is like that. Our house provider offered our house back then for 149,000. The final house price was 195,000 without upgrades from the electrician, sanitary and tiler.
How come?
Underfloor heating, controlled residential ventilation etc. were not priced in.
For some others here, it's a no-go if a house provider hasn't even priced in shutters and underfloor heating, but offers them as additional upgrades.
In this respect, I know that there are houses for under 200,000, but whether you can manage with that sum, I doubt it if you really think about it and want one or the other feature.
If you want to forego polystyrene and build more ecologically, you end up rather with a provider who is attached to a higher segment. They then also install more expensive heating technology, possibly also the ventilation system which in my opinion is important included. This costs well over 12,000. Home builders who can only build cheaply inevitably choose a builder who leaves out one or the other in basic equipment, but then you also have to live with the fact that it is "only" polystyrene or only gas heating.
Everything else in technology you have to be able to afford.
I hope I have made myself understandable.
Calculate on average 180,000€/sqm plus additional construction costs, when building cheaper it can be less, eventually you end up with cheap construction (see construction description!!!), the higher the quality of the construction description, the more expensive it can get.
Yes, and then there is the north/south divide. Downwards it gets more expensive.

Currently, the offers are around 280-300k € for the entire project.