Construction costs are currently skyrocketing

Many thanks.
I will ask what exactly the "preparation" looks like and partially list your points.
I'm inexperienced here. They will probably just answer "a empty conduit will be laid, etc."

So right, even if it gets expensive -> have empty conduits installed?

You can and should also try.
However:
Your general contractor knows what you really want. I find it hard to believe that he will significantly lower the price if you suddenly no longer want photovoltaic and wallbox preparation, but rather a 3-phase outdoor socket with 5x2.5² supply cable and an M32 empty conduit for a "sauna" on the roof...

Spoke with our BL yesterday, HeidelbergCement has announced in writing a price increase of €35 per cubic meter of concrete starting January 1st. This would be an increase of almost 40%…

Here, 150 is now being asked for dry RM beech.
It's only about the ambiance now, you probably hardly save anything.

Well, I think wood has about 1,500 - 2,000 kWh / cubic meter. So that's 7.5 - 10 cents / kWh, still cheaper than new gas contracts.

Well, I believe wood has about 1,500 - 2,000 kWh / cubic meter. So that means 7.5 - 10 cents / kWh, which is still cheaper than new gas contracts.

Exactly, and no one can shut off the wood in my basement. We would now be accepted again as a regular new gas customer by the municipal utilities (for a long time they did not accept new customers at all), but we would pay 350€ per month instead of the previous 65€. With wood, we are simply much cheaper. Maybe it will calm down again, who knows, but it is never wrong to have two different energy sources in the house as an option.

P.S. Anyone who wants to get daily updates on the development should google "Swap Mitte 10 years". finanzen net has the 10-year rate daily dz hyp has daily all rates from 1-30 years at a glance boerse manager magazin 10 years with charts Swap Mitte rate = refinancing rate for banks (simplified)

So the appointment at the house bank "Sparkasse" was as expected.. 3.6% despite increasing equity to 70,000. However, the Sparkasse would have financed it, stating that he is currently one of the few for whom the rates still fit at all. But with almost 1500 euros burden plus additional costs etc. he will decide against it. Today there is still an appointment with mc broker. Let's see what they say. Where did you get these 2.5%? Or what were the conditions to get that?

Where exactly were these 2.5% available? Or what were the conditions to get that?

Not at all!!! Unless the bank is giving away money. That is the rate at which banks refinance themselves. On top of that come all cost items and of course the bank’s profit. That’s why nowadays you end up more around 3.5-4.0%.