Photovoltaic system: Costs, saving potential? - Experiences?

So once again a positive effect and the bill for construction power eases up...

Heating with construction site electricity was not allowed for us. Nobody cared..

You

And can the system also be used for the heat pump to heat the screed (using construction power), provided the house connection has not yet been made?

But you have to make sure that the construction power meter has a backflow preventer, because you are not allowed to feed the photovoltaic surplus into the construction power meter! That would cause trouble!

We had a final bill of €58 with photovoltaic (with storage) on construction power, including screed heating

Is also not permitted with us or explicitly prohibited.

Isn't it possible to program something so that the surplus is simply not fed in? It's supposed to only supply the heat pump. But doesn't anyone (supplier) notice that the initial reading is higher than the final reading?!

Not that it should become too easy with taxes in Germany - where would that lead us?

or that the citizen would ultimately pay too little tax....