Construction costs are currently skyrocketing

That is probably a standard statement from a heating installer just pulled out of thin air. I wouldn't put much stock in it, that's just how things run 'on the construction site' or did he really read through the detailed planning of the energy consultant (which is usually 15-30 pages)? - hardly, why should he. The house is standard size, so it needs standard energy, meaning 1500m3 gas or 5MWh electricity - a bit of buffer, done. Of course, this favors a larger, unnecessary heat pump.

I would react extremely sensitively to that. Behind this exaggerated estimate, there may be massive planning errors that can no longer be corrected afterwards.

But geothermal energy has a higher efficiency, right?

[*]Maximum 30 degrees supply temperature in all heating circuits
[*]Maximum 30 mbar pressure loss in the worst heating circuit
[*]Maximum 30% length difference between the shortest and longest heating circuit
[*]Maximum 30% of the heating circuits with individual room controllers
[*]Minimum 30 mm pipe diameter for connecting the heating circuit distributors

I actually underestimated this point back then, I assumed the same reference value. One underestimates the enormous standby losses in a single-family house, even with deactivated circulation. I would rather assume 2500 kWh for 2 people and then 600-800 kWh for each additional person. In the first year, my circulation ran 24/7 because I didn't have time yet. 2 people, 4500 kWh for domestic hot water - but from the utility room to the bathroom it's also about 15 m, unfortunately