Is preparing for photovoltaics in new construction sensible?

The construction will only be finished in 2023, so not possible immediately

My main concern is whether I can build the terrace roof beforehand without any worries or if I will have problems later when I want to install a photovoltaic system

When will the roof be put on approximately?

A terrace roof - if walkable - might not be a problem. How many floors will there be? There are scaffolds that can be placed in the gutter and supported on the wall below. Getting onto the roof with a ladder next to it should then be guaranteed.

With so much time, many options are possible. For example, to acquire some components at a favorable price point. They only account for about 50-70% of the total costs. But to reclaim VAT, VAT registrations would be necessary. But since you have to pay two years less VAT on revenues because it is not present, I think -> better clarify precisely.

Addendum: I had calculated about 2500 kWh/a feed-in for my planned size. That would be about 50000 kWh in 20 years. With an electric car and some % degradation, rather 40000 or less. The 50 MWh already mean about €60 (depending on reduction) of lost feed-in remuneration per month. In addition, there would be the paid household electricity.

Waiting one year had cost me about €2600.

I had calculated about 2500 kWh/a feed-in for my planned size. That would be about 50,000 kWh in 20 years. With an electric car and some % degradation, rather 40,000 or less. The 50 MWh already mean about €60 (depending on reduction) of lost feed-in tariff per month.

If you get €720 feed-in tariff (12*€60) for 2500 kWh surplus per year, then your feed-in tariff is 28.8 ct. Congratulations. Today you don't get that anymore.

If you get 720€ feed-in tariff (12*60€) for 2500kWh surplus per year, then your feed-in tariff is 28.8ct. Congratulations. You don’t get that anymore today.

Wrong. I described the monthly reduction of the feed-in tariff over 20 years. For shift Feb -> March 2021: (0.0804 €/kWh - 0.0792 €/kWh) * 50000 = 60 € exactly 12 shifts would then already be this 720 €. In addition, there is still what you continue to buy yourself. Note: The monthly changes of the feed-in tariff fluctuate. By the way, I calculated and received the 60 € together with lost household electricity savings from the company (in the form of a reduced invoice amount). ;)

Wrong. I described the monthly reduction of the feed-in tariff over 20 years.

You probably meant that. You did not describe that.

The 50 MWh already mean about €60 (depending on the reduction) feed-in tariff not received per month

So not €60 per month Apparently €60 less total remuneration for every month of later system registration.

You probably meant that. You did not describe it.

It may not have been entirely clear here what "50 MWh", "reduction" have to do with the actual monthly remuneration (which is only a few euros anyway in March):

The 50 MWh mean about €60 (depending on the reduction) of feed-in remuneration not received per month.

But I was much clearer that one does not receive €60 feed-in remuneration per month. ;)