House construction for €750,000 with an income

For a 750,000 EUR project, electricity and additional costs really shouldn't be an issue

I see it the same way. The use of washing machines and hair dryers doesn't change. Maybe some kitchen appliances will even be replaced with more energy-efficient ones. Nowadays, lamps are only installed as energy-saving LEDs... at least when it comes to accent lighting and outdoor lighting. You calculate a buffer of 30% based on current consumption. Heating flat rates can be googled, waste fees are fixed, and insurance can be found online for a calculation in 5 minutes. You already have consumption data for 4 people now.
All in all, you just take 500 € as a placeholder—overcautious 600 €. And as Steffen80 already says: if you then have a bad feeling, you should scale back a bit: reducing the house size by 10% can alleviate fears about some euros.

Does it really make that much of a difference?

Does it really make that much of a difference?

What?

Building the thing smaller?

380000 house minus 40000 basement equals 340000 340000 divided by sqm of 180 equals rounded 1900... I am certainly not a numbers juggler here, but roughly speaking you will probably save 15000 - 19000 € for saved 10sqm. Where does a house start for you? The majority in this forum, which reflects society, build 150/160sqm without basement for 4 people or 130/140 with basement. Thus they lay a foundation for a healthy financing that does not cause any stomach aches. There is also a dressing room and a fancy kitchen included. What does the banker say?

The banker is traveling but absolutely does not want a house under 180 sqm. And definitely a basement. I will calculate everything tonight as soon as two little sweet people under 5 finally sleep here