KfW loan is expected to become cheaper from 01.07.

We are considering... we would have more available monthly next year and there are still a few things to do on the old building that would be subsidized because of energy efficiency. At first glance, the conditions of the KFW didn't seem bad to me, especially since you often get grants. But when I read this here, it might be better to inquire at other banks again.

Your energy consultant charges 5,600 euros?

Yep. Although 2,000 € are deducted by the BU and I get 2,800 € back. I know, quite a lot.

That was not possible with my one concluded in 01/2018. Why should one have canceled it immediately and lost the variable special repayment? It is paid off anyway in 2 years exactly because of its advantage.

Well, the unlimited special repayment might be interesting for those expecting large sums of money or an inheritance. Otherwise, the usual 5% is already a big gulp, given today's volumes.
The KFW was only interesting because of the repayment bonus, and you could easily get that if you had 3 tranches at the bank right away.
1) Main loan
2) KFW (100k)
3) Forward in 6 months on 100k less the repayment bonus at the same bank

I still remember the time when many found KFW annoying because of the conditions and the short fixed interest periods. If you like to fix everything for 20, 25, 30 years, the KFW module simply didn't fit the concept.

monthly annuity

somewhat contradictory ;-)

Well, the unlimited special repayment might be interesting for someone expecting large sums of money or an inheritance.

Certainly, or for anyone who wants to put in an extra 2-3k€ every month to pay off the kfw153 and then subsequently set the repayment of the main loan to the maximum.

But this brings me to a question. If the contract states that the maximum repayment can be set to 5%, then my question is: from which base does the bank start here?

From the initial repayment of 3%, so +2%
or
From the current repayment of 3.3%, so only +1.7%

2. The loan option is unattractive for 95% of home builders/buyers.

Hmm, well, if you browse through the forum, I'm not so sure about that? It seems to be cheaper than most of the conditions seen here recently, or am I seeing that wrong?

Partly, that's certainly due to relatively high loan-to-value ratios, but those also seem to be becoming more common(?). (For years now, the trend has been toward higher construction/purchase costs, but low interest rates... which probably doesn’t make a huge difference in total costs over time relative to income compared to before, but it does mean that saving 1-2 years’ salary only covers the incidental purchase costs and the loan-to-value ratio is correspondingly high)

This is just my impression from browsing the forum, but so far the loan option doesn’t seem that unattractive to me.

The renovation loan has become cheaper. The predecessor was from 0.75%, now from 0.66%