So I moved the slide rule once and now consciously take out only one building block, the largest one with the highest interest rate, to show that the whole thing is not so dramatic because of the home savings contract, provided I have not miscalculated.
There are 205,000 € with 1.9% interest over 15 years. Until now, I thought you pay down directly, then there is a residual amount and after that you have 2.35% – which sounded very good, but unfortunately was not the case because it is a home savings contract.
BUT:
With this variant, after 15 years there remained a residual amount of 140,000.
If I calculate the home savings contract; i.e. that you continuously pay the interest as in the first full month, then you pay a total of 58k interest at 1.9% and save 55k – resulting in a residual amount if you then virtually add these 55k to the loan of 150 or... 149k. Certainly more, but not as extreme as I thought before the calculation.
If I apply all this to both home savings contracts + KFW and then calculate so that after 15 years I pay my same monthly amount in II and III and then make an interim calculation after 20 years, because then the KFW loan will have expired, I have the following after 20 years:
33k residual KFW (unknown interest from then)
177k residual II and III (after 15 years it was 222k, monthly at 2.35% and 1,058 rate)
Until then, I have paid my 1,250 Euro monthly (plus the expensive 20k loan 160 Euro, which would also be finished after 20 years, even if I didn’t pay anything extra)
So total outstanding after 20 years:
33k KFW
177k the rest
= 210k -> assuming it continues at 2.35% for this amount and I then pay the same total 1,410 Euro monthly, I would be finished after 14.5 years, so after 34.5 years total.
If the home savings contracts were not home savings contracts but you would pay down directly, I would be finished 6 months earlier, so about 10k more expensive overall.
I am still a bit surprised about this, whether there is perhaps a calculation error... but it should fit.
Certainly, I do not know if you would get 2.35% for the 33k remaining KFW and how long it would be secured, but that never sounds bad and I would have a permanent rate of 1,413 Euro.