Construction of a 144 sqm bungalow in Fichtenwalde (near Potsdam)

There must be a reason why almost everyone gets the VAT refunded ;). You also have business expenses that you can claim. The private use can be declared as a flat rate of 20 cents. If it were a loss-making business for private individuals in the long term, it would have been widely known by now and hardly anyone would register as a business anymore.

And what about the issue of compulsory hobby loss?

And what about the issue of forced hobby activity?

It's not a problem. You also feed electricity into the grid and get paid for it. So there is a permanent source of income and thus the intention to generate profit. In the end, you break even or have a small tax loss or gain. Typically, hobby activity rather applies to occupations like photography. Equipment worth several thousand euros is purchased and claimed, but one never seriously engages in it because it is actually just a hobby that one tries to get subsidized.

No problem. You also feed electricity into the grid and get compensated for it. So there are permanent income streams and therefore an intention to generate income. In the end, you break even or have a small tax loss or profit.
Typical for hobby activities is something like photography. Equipment worth several thousand euros is purchased and claimed, but one never seriously engages in it because it is basically just a hobby that one tries to get subsidized.

Does that mean you have to register a business with the tax office before buying the photovoltaic system?

Does that mean you have to register a business with the tax office before buying the photovoltaic system?

Yes, but you can also do that shortly afterwards. It is at least better than submitting everything only with the tax return. Then the processing usually goes significantly faster. What you also need to keep in mind is that in the year of commissioning and the following year you have to submit monthly advance VAT returns. After that, due to the amount of income, usually only an annual VAT return has to be submitted.

A question regarding the floor plan. We are considering, if it is still possible at all, to omit the terrace and instead enlarge the living room. As mentioned, we do not know if this will even be possible. However, we would gain about 11 sqm without significant additional costs (the roof is already planned, as is the base slab).

What do you think about this? Does the building application also need to be adjusted for this? Is an addendum sufficient, or would we have to start from scratch?

I think it’s good that you are dealing with the floor plan.
The extra space in the living room feels good.
So far nothing has been built, everything is just on paper.
To what extent the building application is affected, your [GU] or the building authority will tell you.