KFW 270 for subsequent photovoltaic system

I would try it again at a real bank. One with real people. Then plan the investment as large as possible and present the earnings calculations to the banker. Then print out the guaranteed Renewable Energy Act rate and have the payments from the grid operator go directly into a separate account of theirs. If the advisor then doesn't realize that this is an absolutely risk-free undertaking, I don't know either.

But you have to leave out the storage (better just omit it), it can't be made to look better.

If the consultant then doesn’t realize that this is an absolutely risk-free undertaking, I don’t know either.

Then start pulling your hair out. That may be pragmatic without much risk, but formally it’s just as if I lend you €20,000 for a world trip and have no security of getting my money back.

Then print out the guaranteed Renewable Energy Act rate

And as a consultant, I then tell you who guarantees me that you as a customer, including the storage, won’t almost entirely consume the electricity yourself for the house and electric car? The Renewable Energy Act rate is not worth the paper it’s written on (for the bank).

have no security,

Except for a legal regulation.

completely spend alone on house and e-car?

THAT would of course be the worst case. Suddenly the borrower gets 20 instead of 6 cents per kWh. No, you’re right, that quickly ruins the calculation. ;-)

But that’s exactly why I say you have to talk to someone about it. If I enter the data into an online loan calculator, of course it says no. If the advisor is not knowledgeable, you have to possibly explain to them that a loan for photovoltaic is the only loan for a private person that improves the customer’s financial situation and does not incur additional costs like most other loans the bank issues.

Well, but how big is the risk for the bank with 15,000€?

When I am in the ING app online banking, I occasionally get ads from ING, instant credit of 35,000€ without a check. But for a small loan for a photovoltaic system, they want collateral? Sure, the interest rate will be significantly above that of the KfW, but it is somewhat incomprehensible.

But as I said, thank you very much for the clarification.

THAT would of course be the worst case. Suddenly the borrower gets 20 instead of 6 cents per kWh. No, you’re right, that obviously messes up the calculation quickly. ;-)

No, you don’t get anything in your account at all. You only have a lower electricity bill. So exactly 0€ arrives in the separate account at the bank where you want to park the guaranteed payments. That completely messes up the formal calculation.

Well, but how big is the risk for the bank with 15k€?

As big as with any consumer loan. But that doesn’t cost 0.99%, it’s 3.99% and more. I’m only talking about the formal risk – regulatory, with everything that comes with it. How often do I have to refuse financings (e.g. kindergartens with municipal lease agreements + municipal guarantees), because although they’re considered a "great deal" by everyone, they are simply not formally financeable.

To make it interesting for oneself and the bank, one should really cover all areas and, if possible, build > 20 kWp. If there is space, a sensible size is usually limited to 30 kW by the house connection. Depending on the roof orientation, that corresponds to about 40 kWp. Then we're already talking about €50,000.

For the mid-terrace house, which hopefully can accommodate 5 kWp, one usually does not need a bank for support.