Photovoltaics at any cost - current situation and offers

For a heat pump, a storage unit is not worthwhile. Rather for the night, so that it empties every day.

Roughly estimated with average values: 200 cycles/year, 7 kWh/cycle -> 1400 kWh/year through the storage.
Electricity price 40ct/kWh - feed-in tariff 8.6ct/kWh -> 440€/year
7800€ acquisition cost divided by 440€/year -> the storage must last almost 18 years.
Realistically, probably only half the lifespan.
From this, it can be deduced that either electricity must become twice as expensive or the storage half as expensive to break even.
Since storage units are also not good for the environment, I would currently rather refrain from using them.

But it probably also depends on the consumption pattern. For example, if you mainly have consumers at night that you can't shift to daylight hours, then it might shift again. And by now, you can probably expect at least 50, rather 60 cents / kWh if you don't want to reckon with an annual increase anyway.

Around 15% charging/discharging losses must also be deducted. Currently, prices are simply not in economically reasonable ranges. My 10.2kWh storage system cost €4200 in 2020 after VAT and subsidies.

But it probably also depends on the consumption pattern. For example, if you mainly have consumers at night that you can't shift to daylight hours, then things can shift again.

There may be a few special scenarios, but how realistic is what was mentioned in a single-family house?
And nevertheless, there will always be days when you can't fully charge the storage.
Especially with a heat pump and "only" 10 kWp, there will be plenty of days in winter when nothing goes into the storage.

And by now you can probably expect at least 50, rather 60 cents / kWh if you don't want to factor in an annual increase anyway.

Well, whether that is realistic remains to be seen.
Many are already protesting at 40 ct and caps are being introduced.

Well, I have no idea how widespread that is. My wife is a plant aficionado, and tropical plants just need extra lighting. Then there are aquarium owners, gamers, sauna users, shift workers, possibly home office night workers. Yes, certainly not the majority. But if you know that you have more or larger consumers at night, you can calculate more precisely, that’s what I wanted to say.

Yes, you just need a lot of space for winter.

How long should the lid last? I think that even if market prices go down again in the medium term, prices will stabilize well above 40 cents. I mean, right now we have almost universal coverage over 50 cents with new contracts. With existing contracts, one supplier after another is following my increase from 25.xx to 52.xx (just received). That won’t seriously go down again, and the state will not subsidize forever. That means these prices will form the new base level over the next two years.

The casual answer will just be to save even more electricity.

BTW, how is it actually with DIY batteries? There are some on special interest platforms and forums. Is that even legal? In off-grid operation? I’ve read that you can connect car batteries (I mean the 12V lead-gel ones) for that?

Regarding the question aspect: "at any cost?"

In a - for me believable - article I have read that batteries in the future will very likely not only become significantly more powerful but also more environmentally friendly. To strengthen the system, it is helpful to participate, even if it is not yet "worthwhile" economically.