Photovoltaic system air-water heat pump - profitability single-family house KFW55EE

Have a lot of window areas (100m2) and, due to their size, expect an energy consumption of 7-9k kWh p.a.
Heating is done by underfloor heating with the Tecalor THZ 504 air-water heat pump.

You probably won’t benefit much from the photovoltaic system in winter. In good weather, you will heat with solar gains and are likely to get rather too warm than too cold. In bad weather, the photovoltaic system delivers relatively little electricity compared to the heat pump. The low roof pitch reduces efficiency even further in winter.

For profitability, it will be more decisive whether you can also consume the electricity in summer. In other words: Are you home during the day?
The same question arises with bidirectional charging. How often does the electric car leave in the morning and only return in the evening?

If he can charge for free at the employer, it will then arrive almost fully charged at home. The question would rather be whether this is not a taxable benefit that must be taken into account for tax purposes (regardless of whether the employer puts up with it for long).

When will construction take place, and by when would you need to decide on the photovoltaic system? There will certainly be short-term changes in approval, bureaucracy, and subsidies for photovoltaics. Probably not for the worse. In this respect, I would look for a solar technician with whom you plan this, but possibly only give the official order after the new regulations are available. If you have to finance it completely yourselves, that’s not a problem. There are KfW loans for that as well, and usually the installment is easily covered by the feed-in tariff or your own electricity savings.

What kind of roof is it actually? A shed roof, facing south?

We have the THZ 504 in use in a KFW55 house. In 2021, we covered about 14% of the energy costs from photovoltaics (4.55 kWp with relatively ideal roof pitch and orientation), the rest came from the grid. In the months when the system draws the most electricity, you have extremely little generation from photovoltaics. You have good synergy in the transitional months of autumn and spring. Also in summer for hot water and ventilation. However, we also have a software component that converts the photovoltaic energy surplus into warmer water before it is fed into the grid. I am still absolutely pro photovoltaics. We have practically financed ours as well. There are few other investments that practically pay for themselves.

When will construction start, and by when do you need to decide on the photovoltaic system? There will certainly be short-term changes in approval, bureaucracy, and subsidies for photovoltaics. Probably not for the worse. In this respect, I would look for a solar installer to plan with, but possibly only award the official contract after the new regulations are in place. If you have to finance it completely yourselves, that's not a problem. There are also KfW loans for that, and normally the installment is easily covered by the feed-in tariff or your own electricity savings.

What kind of roof is it actually? Shed roof, facing south?

Construction start is around May/June 2022, completion spring 2023.

I thought so too, but the subsidies will certainly be passed on by the providers.

Gable roof 15° pitch (roof surfaces are on the north and south).

We are using the THZ 504 in a KFW55 house.
In 2021, we covered about 14% of our energy costs with photovoltaics (4.55 kWp with a relatively ideal roof pitch and orientation), the rest came from the grid.

Ouch, since I am currently in the process of buying photovoltaics myself, the 14% reads like a slap in the face. Why so little? Why generate hot water instead of feeding it in, even if it’s only 7 or 8 cents?