Hello, such a storage system is currently not cost-effective anyway, no matter how you twist and turn it, unless you are calculating with electricity cost increases of 5% p.a.
Now, about the tax part... only a member of the consulting professions is allowed to advise you there.
But two points to consider beforehand: You don’t necessarily have to go through all the effort if you have no other business; then you are also not allowed to reclaim the VAT. If you are commercially or freelance active, there is no way around doing this. Hiring a tax advisor just for that is probably not worthwhile.
Continuing with the economic part... If you decide to do it, fully load your roof. Covering only 50% is silly, because in winter you won’t get very far with the planned size of the system. Overall, it may reduce your yield somewhat, but feeding in the surplus will eventually get you to break-even (as opposed to the storage).
The storage is only for the soul and as a hobby. More than that is not possible at the moment.
For orientation, even if it doesn’t quite fit since we have a ground-source heat pump (these are the peaks)
Here is today’s dark gray day, so even with 10kWp we wouldn’t have fed in anything today.
This was yesterday with some sunshine...
Here is a laundry day with good weather at the beginning of November.
And this was our best day this year in midsummer
