Photovoltaic systems: What experience have you had?

That's correct: I think around 600-700 gas will be added.

Then explain why that is nonsense? I still haven’t quite understood why thousands of photovoltaic operators make the same mistake year after year ;-)?

Just because you pay a power installment and at the same time get money for feeding in?
The end result counts.

Whoever says in the photovoltaic field that a battery system pays off is talking nonsense. There is a lot of sugarcoating/calculating going on at the moment.
The subsidies look interesting at first glance and at second glance are a scam. No one tells you that the battery probably won’t last the 20 years of feeding in. And you still need power from the grid at least in winter.

I’m leaving out the purchase price completely anyway.

But if someone here writes that you can achieve €0 energy costs with a photovoltaic system, that is nonsense.

You pay a 1,400€ advance and receive 900€ remuneration. Where is the profit? Or at least where are the 0€ costs?

It is actually quite simple: Your calculation is wrong. Without photovoltaics you would pay 2,000€ for electricity, with photovoltaics you pay 1,400€. Your savings of 600€ are already included here. That is why it must not be deducted again at the end.

You can’t just go and say: The pants normally cost 100€. I negotiated well and got a price of 80€. And because I saved 20€, the pants cost 60€ in the end.

Anyone in the photovoltaic sector who says a battery system pays off is talking nonsense. A lot is being sugar-coated / calculated nicely at the moment.

But that looks different again when the storage system is practically given away by the KfW. Then the storage system also begins to pay off. For example, it was clear to us from the start that we would build KfW 40; the last necessary step to 40+ was the storage system. Due to the two residential units, we receive a repayment grant of €30,000; without storage and "only" KfW 40, it would have been only €20,000. This additional repayment grant of €10,000 therefore easily covered the 10.5 kW storage system and cost me practically nothing. It's like the chicken and the egg: if we hadn't chosen the storage system, the grant would have been €10,000 less; with storage, it's more, which then immediately went back into the storage system. Thus, the storage system is free and pays off from day one. Just the fact that we integrate the photovoltaic system and the storage for screed heating (air-water heat pump) alone significantly reduces the arising costs.

I haven’t included the tax aspect in my back-of-the-envelope calculation.

So I am roughly 100€ ahead per year

The calculation like this is really worthy of a milkmaid.

Without photovoltaics you pay 2000; with photovoltaics 1400 minus the compensation of 500. (Tax left aside).

In other words, a 1500€ yearly difference is opposed to the investment, the return on equity or the financing costs, as well as maintenance and repair costs and depreciation (or a clearly larger reserve for replacement in x years); and then you arrive at an ROI of x years.

But to talk about having 0€ or even negative energy costs...

Kfw40+ also has disadvantages :-)
- Interest conditions are mediocre
- Meanwhile, no early full repayment is possible without prepayment penalties
- feed-in limitation of 60% - for 20 years, regardless of whether the storage lasts that long or not
- for tax purposes, due to the higher self-consumption with a battery, the tax office must be involved for at least 5 years.

The tax office takes a share of the kWh of electricity you feed in, not the 70% that you get back yourself.

But it looks different again if the battery is virtually given away by the KfW. Then the battery also starts to pay off. For us, for example, it was clear from the beginning that we would build KfW 40; the last necessary step to 40+ was the battery. Due to the two residential units, we receive a repayment grant of €30,000; without the battery and "only" KfW 40, it would have been only €20,000. This additional repayment grant of €10,000 has more than covered the 10.5kW battery and cost me virtually nothing. It's like the chicken and egg scenario: if we hadn’t taken the battery, there would have been €10,000 less in funding; with the battery, there was more, which went right back into the battery. Thus, the battery is free and pays off from day one. Just the fact that we integrate the photovoltaic system and the battery for screed heating (air-water heat pump) significantly reduces the costs incurred.