Home purchase financing - we cannot decide

Gladly
The offers have been improved again. We have decided on Offer 2.
KFW is not included in the calculations, as it is identical in both offers.

Offer 1:
- (Loan KFW 50k, RS 34k after 10Y)
- Loan 303k, 20Y fixed, 2.15% (2.17% eff), term 30Y, RS 121.2k, special repayment 5%
-> Interest expense first 20Y without special repayment: 94.2k, RS 121.4k
-> Total cost of loan with scheduled term and without interest changes and special repayment: 410.4k, rate 1353

Offer 2: Our choice
- (Loan KfW 50k, RS 34k after 10Y)
- Loan 100k annuity, 15Y fixed, 1.89% (1.91% eff), 2% repayment, special repayment 5%, term 35Y, RS after 15Y without special repayment: 65.4k
- Loan 203k via building savings contract, interest 1.52% for 12Y, then 2.35%. (Total term 28Y), first building savings contract phase special repayment 5%, second building savings contract phase special repayment unlimited possible, RS after 20Y approx. 69.7k
-> Total interest expense first 20Y (projected with 15Y annuity at constant interest to make it comparable): 85.1k, RS 121.4k
-> Total cost for both loans with scheduled term and without interest changes and special repayment: 404.3k, rate 1333

Offer 2 is thus cheaper than Offer 1. The interest rate for Offer 1 would have to be below 2.35% after 20Y and an RS of 65k (this is the interest rate risk of Offer 2) in order to achieve an interest expense of 87k with an annual special repayment of 2350 and a constant rate. However, this interest expense is still higher than the interest expense of Offer 2 and here special repayments are not yet considered! Offer 2 is therefore definitely more cost-effective.

Conclusion: Advantages compared to Offer 1: total cost lower, 9.1k interest saved, interest rate risk reduced from 121k to 65k (without KfW), 20€/month less, 58% of the total amount is secured by the building savings contract for the entire term, unlimited repayment possible in the second building savings contract phase.
To make both offers comparable, an assumption of 0€ special repayment was made in the calculation.

For the 34k KfW RS we are still considering taking out a small building savings contract, to use it in 10Y depending on the interest rate level or to continue saving for the RS of the 100k.
Special repayments are of course planned and realistically possible at a minimum of 2k annually. At the beginning certainly more than 2k special repayments to benefit from the compound interest effect.
This is how our schedule looks, which I find very good.

What do you think about it?

No feedback whatsoever? Hope the effort to write it down was not in vain

Are there any fees charged for the building savings contract? Are these taken into account in your calculation? What are the effective interest rates (total) of the two variants?

I find it difficult to follow the calculation from your post :-(.

Thank you for your feedback. 1% building savings contract fees are already included. Effective interest rates are indicated everywhere except for the building savings contract, completely forgotten. Saving phase (12 years) 1.52 nominal and 2.08 effective, loan phase (16 years) 2.35 nominal and 2.52 effective. The calculation was done by the trusted bank advisor. Sounds almost too good to be true, but I can understand the calculation. Maybe I am forgetting something?! How else can I compare the two offers?

That's tricky, you need the effective overall interest rate (so one number each for option A and for option B; not two or three each) as a starting point, section 4 on this page: http://WWW.iww.de/Bebauungsplan/Finanzierung/Immobilienfinanzierung-teure-bausparkombinationsfinanzierung-f66380

From me you get the diligence and feedback like

Greetings