Subsidies: how effective? And sensible when using own funds?

It always depends on the average interest rate: If we were to normally borrow the planned 100k euros from KFW153 through the bank, we would pay about 10k euros more in interest at the currently offered interest rate (term: 10 years as an example period, since the fixed interest period of the KFW loan is 10 years). It is due to the large difference between the bank's interest rate and that of the KFW bank and always needs to be checked individually.

I would most likely look into whether a geothermal heat pump with a ground collector is feasible. In my opinion, this offers the best subsidy when combining BAFA and the 10,000-houses program (at least 6,000 euros). Of course, costs for the production of the collector surface also apply here again, but from my point of view it is still currently the best way to really benefit from a subsidy (besides KFW153 and KFW431, if additional costs are not astronomically high).

Thank you, Haydee and Strahleman

Did you have to pay processing fees for the KfW loan?
I have read that 4% fees are allowed. There was an incident with the Raiffeisenbank: the court ruled in favor of the bank (so €4000 on a €100K loan!!).

Is the condition for a KFW153 loan always 0.75% p.a., regardless of the bank?
And are there any other costs / fees at all?

Unfortunately, a geothermal heat pump with surface collectors is not possible for us, as we still have an old building on the property.. BAFA is therefore excluded.

The KFW sets the interest rates for its loan. The executing bank has no influence on this. No additional costs have been incurred by us through the KFW loan (main loan at the Sparkasse). Even in the mortgage, they are not included. It only states Sparkasse there, but for the ENTIRE (KFW+Sparkasse) loan amount.

Thank you, Sebastian! I just spoke with Sparda Bank, the advisor was surprised that there are still banks charging fees. Sparda certainly does not do that. I am attaching here my calculation for a KfW153 subsidy (= what the subsidy would cost with the current fees and interest rates). Maybe it will help other seekers: Interest at 0.75% p.a., effective interest for 10 years: €4610 (according to the bank no possibility of early repayment) 1+2 (notary fees + land registry): €930 (varies) Energy consultant (50% of total costs): €475 (varies) ================ €6015 For us (KfW 55, equity) it is not worth it. We are currently focusing on the 10,000 houses program. With air-water heat pump, photovoltaic with storage and possibly wood heating with storage and 2-story house there would be around €8,000-10,000 subsidy together

We will probably stay away from all subsidies, although it sounded so tempting at first.. for possible interested parties here are our considerations regarding the 10,000-Houses-Program:

to achieve the required heating values, we would have to insulate to KfW-40 (and install a ventilation system with heat recovery, which we actually did not want).
For the required performance figures, larger systems (or systems installed indoors) with >7kW would have to be installed = more expensive and less economical for us.
If there is still something left in the subsidy pot, there would be €3,000. But only if the air-water heat pump has a heat meter plus thermal storage.
Photovoltaics only get a subsidy combined with a smart meter: for data protection reasons alone, we personally do not want that.

Of course, this is all a matter of attitude and taste. And with poorer creditworthiness, such programs probably help to get a loan.
"Not everything that glitters is gold" is what comes to my mind first with such subsidies.

We also didn't receive anything. I think a passive house is quite energy-efficient. What more do they want. We also achieved the energy efficiency bonus in 2017. It was only available if the technology bonus was approved. But we didn't need that.