Photovoltaic systems: What experience have you had?

What does KfW40 cost you compared to "normal"? It's not free, is it?

OK. Then, to be fair, you first have to deduct the costs that building KfW40+ actually entails and which produce 2 residential units. The gifted storage is basically financed through the costs for the Kfw40+ requirements ... so it’s a bit of creative accounting. But that’s totally fine. My better half didn’t want such a thing in the basement, but that’s another story. Which storage unit should it be? Tesla is interesting in terms of cost.

That is of course a point, but if, like in our case, the 2 units are fixed, as well as KfW40, then I’d be silly not to take the storage for free... @Mastermind, our future base fee is €9.60 per month

What is considered "normal"? We don't have gas, so a heat pump... We wanted ventilation anyway, the exterior walls and the roof are standard KfW40... Only the thicker perimeter insulation was missing....

Normally it is the Energy Saving Ordinance 2016, KfW40+ is not without reason. A heat pump and controlled residential ventilation alone do not make a KfW40. You need more insulation on the floor slab, basement, facade, roof, windows and then also an expert, airtightness ... that is not given for free.

Keep dreaming. Go to the photovoltaic forum and read every post where someone got the battery for free.... None of the calculations ended up with it being free...

Storage is viewed critically there due to its typical uneconomical nature, but under your conditions with KfW40+ it could have a significantly less negative impact than usual. Maybe even slightly positive. Have it calculated precisely.

Ultimately, the profitability strongly depends on the price of a system. You need a reasonable provider who can offer competitive prices. Whether that is the case with a complete house provider, I cannot say. The above-mentioned 1100 - 1300 €/kWp (excluding VAT and storage) are already a good reference point.

With our photovoltaic system provider, I pay €922/kWp without VAT and storage. I think this is a good offer, but it also required quite a bit of negotiation.