Passive house as a logical consequence? Are there counterarguments?

The photovoltaic system + battery costs €23,000

...so €27,000 surcharge from the Energy Saving Ordinance to Passive

Ah, you also had to deduct the fireplace, as it was probably not included in the Energy Saving Ordinance reference house and is also not needed for the passive house.

The fact that I still receive money from feeding electricity into the grid, because I certainly won’t consume 9000 kWh per year and energy prices will also continue to rise, has not yet been taken into account.

Please correct me if I’m wrong, I’m not very familiar with the system.

In winter or when photovoltaic doesn’t produce enough due to bad weather (in summer it will probably be enough for your consumption), you have to buy additional energy for heating and consumption electricity... at a more expensive price than you get for selling it?!

no, the fireplace was also included in the energy saving ordinance.

In winter or when photovoltaic doesn't produce enough due to bad weather (in summer it will probably be enough for your consumption), you have to buy additional energy, for heating energy and consumption electricity... at a higher price than you get for selling?!

...exactly

I can feed in for 11 cents per kWh (the price is legally guaranteed for the next 20 years)
When the sun shines, I heat my buffer tank and charge the battery.
When the sun does not shine, I use the warm water from the buffer tank, when that is depleted via an instantaneous water heater. I get electricity from the battery first, when it is empty I buy additional power and at the end of the year in the final accounting, purchase and feed-in are balanced out

I get 12.50 cents per fed-in kWh, just checked again...

I use the hot water from the buffer tank, when that is exhausted, via an instantaneous water heater

Will you then have an instantaneous water heater everywhere, that is, at all hot water taps?
The buffer tank should be depleted quickly if several people use hot water in the morning...

Do you have to pay taxes on the income of 12.5 cents? I think so, because as an entrepreneur you have to present a balance sheet/income monthly?!