Economic Efficiency of Photovoltaic System and Storage

Keyword VAT refund - but then I have to do these advance returns monthly and tax the own consumption? Does that pay off in the long run?
Generally: Are there calculators on the Internet that calculate everything sensibly? Including tax topics etc.? A complete calculator, so to speak

Complete calculator? A piece of paper should roughly suffice.

Our tax office only does VAT advance returns quarterly in the first year and then annually. And you also have to tax the own consumption or take it into account in the income/expenditure statement. But it’s just a bit of paperwork. Nothing wild.

Leave out the storage or size it significantly smaller. Exception, you are simply storage fans and want to install more modules on the roof later. So far, I have seen roughly two to three times as much power on the roof as fits into the storage when sizing. The price without storage is perfectly fine. Currently, it is difficult to get below €1400 /kwp in sizing.