Introduction to Photovoltaics (New Construction)

Hello,
I would be interested to know the opinions of the experts here in the forum about our project:
Kfw 40+ house in timber construction (not post-and-beam construction) with 2 apartments, definitely photovoltaic, since the purchase of an electric vehicle as a second car is planned within 3 years. With 40+ and 2 apartments, we get a €10,000 repayment bonus more compared to Kfw 40 without photovoltaic and storage, which would cover almost half of the system.
My questions about this:
What does the economic feasibility look like if the repayment bonus for photovoltaic and storage is included?
How large should the photovoltaic system and storage be in this case?
I tend to go for a larger photovoltaic system (at least 10 kWp and about 6 kW storage) because of the electric car, which can largely be charged during the day. The roof is sufficient for this, a north-facing shed roof with 9°, photovoltaic therefore on mounts. Additionally, about 4 kWp would be installed on the south facade and the 12 m wide south balcony at a lower inclination of about 20°.

As already written before and often discussed, the storage does not pay off. It will especially not pay off if you already have a storage in the form of your electric vehicle!

As already written before and often discussed, the storage does not pay off. It will especially not pay off if you already have storage in the form of your e-vehicle!

... because the vehicle is always at home when the sun is shining?

... because when the sun is shining the vehicle is always at home?

Especially since electricity is also generated when the sun is not shining..

... because if the sun is shining the vehicle is always at home?

No, but the profitability of the storage system largely depends on the storage being charged and discharged as often as possible (fully) during its (short) lifespan. And that does not happen if the size of the photovoltaic system is, for example, too small or there are other large consumers (heat pump, electric car), meaning self-consumption is already good even without storage.

I will link to myself here:


If KFW40+ can be achieved and only storage and visualization are really missing, i.e., photovoltaic, controlled residential ventilation with heat recovery would also be implemented even without the subsidy, and the building already meets Kfw 40 standard in terms of insulation (probably very easy with timber construction), plus there are two residential units - then the storage is worthwhile because it is virtually free.

No, but the profitability of the storage primarily depends on the storage being (fully) charged and discharged as often as possible during its (short) lifespan. And that does not happen if the size of the photovoltaic system is, for example, too small or there are other large consumers (heat pump, electric car), meaning that the self-consumption is already good even without storage.

I’ll link myself here:


If KFW40+ can be achieved and only storage and visualization are really missing, i.e. photovoltaic, controlled residential ventilation with heat recovery would also be implemented without the subsidy, and the building already reaches KFW 40 in terms of insulation (probably very easy for wood construction), plus two residential units are added – then the storage is worth it because it is practically free.

... I’m late, but better late than never:

If a small business is registered according to §19 UStG, the sales tax on self-consumption is waived.
If no small business is registered, input tax on the system costs can be reimbursed, but sales tax on self-consumption applies.

The statement about linking photovoltaic system, battery storage, and battery electric vehicle is not correct as such or at best too general, but I do not want to elaborate here.

Have a nice day.