Consultation for photovoltaic systems

How much is that in €/kWh?

400 Ah x 12.8 V = 5,120 Wh = 5.12 kWh ~1000 EUR / 5 kWh ~ 200 EUR/kWh

The profitability of a storage system can be easily calculated.

In my case, I would be able to use about 2000 kWh more, which would be lost to me without storage. At 37 cents electricity purchase cost per kWh, that would be a saving of 740 euros annually. The storage system would then pay off after 7 years. Provided the electricity price does not rise further. With further electricity price increases, correspondingly more.

Apart from that, there is also a backup function available, that is, an emergency power supply in case of a blackout.

The profitability of a storage system can be easily calculated.

In my case, I would be able to use about 2000 kWh more, which would be lost to me without storage. At 37 cents electricity procurement cost per kWh
Here is a link where you can nicely calculate such scenarios.

Such statements with the 2000 kWh are pointless. For that, you would have to give us your values like total consumption, etc.
In the new house, we will have a total consumption of about 4,000 kWh, of which 2000-2200 kWh will be for the heat pump. Where exactly can I achieve your mentioned savings again with a storage system?
In the photovoltaic forum, there are enough experts, almost all of whom speak against the use of storage (for economic reasons).
It may look different with possible subsidies for storage systems in individual federal states.

, your calculation is missing the lost feed-in tariff, 20% storage losses, maintenance charging in winter, and (at least for most) still VAT.

Also, you have to manage to push 5.5 kWh through the storage daily. With the 7kW on the roof, in my opinion, not even close to possible. I guess a maximum of 3 kWh. With heat pump and e-car, then only one remains.

Nothing there is pointless. I can already tell you that the 4000 kWh will not be enough for you. They assumed electricity prices with an annual increase of 6 percent. Not 60 percent like many experienced just this year. At prices beyond 40 cents, however, a storage system does pay off now.

And what happens now. Everyone starts installing storage systems again. And few understand my calculation.

At almost 40 cents per kWh and an annual consumption of 5000 kWh, I pay 2000 euros for electricity per year. With storage, I have a self-sufficiency rate of 75 percent. This reduces my electricity purchase from the grid operator to only 25 percent. Or effectively to only 500 euros per year. So 1500 euros more remain in the household budget. Every year. With an investment sum of 11,000, not a bad return.

And whether I watch currency depreciation helplessly while my money idly sits in a non-interest-bearing account or it is on my roof, in the end it’s completely irrelevant.

Not by 60 percent like many just this year.

You can rationalize anything. Last year, the electricity price increased by about 1% on average. This year will be exciting; in the end, we'll have to see. For me, it was 3%. But your last sentence is absolutely right: Better a full roof than the bank account. And if you still have too much, you can gladly put some in the basement. But please only after that. Think of the children! ;-)