Photovoltaic system: Costs, saving potential? - Experiences?

So... I just checked again and also did the calculations.
Value-added tax on self-consumption in the calculated year would be €242.40.
Income tax on feed-in amounts to €77.50.

Although a large part of that would also have occurred without the storage. If I only consider the tax on the stored electricity, I am at the €100 you mentioned for the 2,700 kWh. But from that I would have to subtract €46, which I would pay on the 2,700 kWh anyway if I fed it directly into the grid without storage.
So instead of the €513 savings per year I calculated, it would only be €467 for the storage.
6,000 / 467 = 12.85
So it would take one more year for the storage to pay off.

I know the entire calculation is not 100% accurate, since the investment in the photovoltaic system without storage would pay off sooner than with storage.

Actually, I just wanted to determine whether the statement that a storage system is basically always unprofitable is true.

I can't yet judge whether the price increase will also reach us soon.

Yes, I'm very curious about that. ;-)

Our consumption is about 9,000 kWh per year because we have an air-to-water heat pump.

House very large or poorly insulated? Heat pump poorly adjusted?

The VAT has no effect on the cloud contract, as it must be paid anyway, with or without the cloud contract.

Does the tax office accept that you reclaimed the VAT?
If you waive the feed-in tariff, there is no longer any intention to make a profit, right?!

Actually, I just wanted to find out whether the statement that a storage system is basically always unprofitable is true.

It's certainly not that generally applicable. But many conditions have to be met, and above all you need the luck that your battery lasts a long time. You can see for yourself that with the remaining small adjustment factors you end up somewhere around 15 years until the break-even point. It can go well, or not. We ourselves also decided in favor of it, with storage costs amounting to only €4300 after subsidies, and even those were recognized as depreciable.

Does the tax office accept that you reclaimed the VAT?

Interesting question. Senec receives the tax payment, but according to my interpretation of the explanations in the videos, they probably do not remit it. I would have a tax advisor check this arrangement, so that the tax office doesn't come around later with a hefty back payment and legal proceedings.

House very large or poorly insulated? Heat pump poorly adjusted?

Simply a very high electricity consumption. Everyone likes to shower very much and very long (especially the children sometimes until the 325l of hot water are gone :p) and in general we are not exactly economical when it comes to electricity consumption.

Does the tax office accept that you reclaimed the VAT?
If you waive the feed-in tariff, there is no longer any intention to make a profit?!

I have ceded the feed-in tariff, but still have to pay taxes on it if I understood correctly. But I need to clarify that again. I still have to do the tax return for 2020.

The deadline for the value-added tax has long since passed.