Photovoltaic system that covers its monthly costs by itself and amortizes

Just a counterquestion, how is a system supposed to pay for itself from day one (with 9.9kwp photovoltaics & 8kw storage) given an estimated €20k investment (which is still financed)?

That means: The savings + remuneration cover the financing rate. That should roughly be possible without storage over a 10-year term. With storage, a longer financing term would probably be needed.

Can you say in general

no, you cannot say that in general.

Those who source the modules as directly as possible from Asia get them almost for free, those who can also do most of the installation themselves and with the help of friendly installers/electricians pay almost nothing in the end and it pays off within a very short time.

Those who already have to go to a professional for the planning (preferably to a general contractor) and pay absurdly overpriced prices there, like for modules from formerly German production, and have everything "done" for them, will hardly see a payback within the projected service life.

I also considered that briefly, but without storage only 30% can be self-consumed, the self-sold & self-consumed must be taxed, interest is paid on the 12k€ loan, something breaks.

All those ROI calculators from the solar companies just don't factor that in.
So in my opinion, not all of the monthly 100€ will be recovered over 10 years.

However, photovoltaics are still a good contribution to reducing the electricity bill. No question.

storage only with subsidy. that's easily €6-10k that you will never get back.

Storage only with subsidy. That's easily 6-10k € that you'll never get back.

I think, but this is just a gut feeling, that it is slowly developing from a hobby (regarding storage) to a useful and cost-neutral item. But of course, only under certain conditions. For existing systems, a hybrid inverter must be present and for new systems, every kind of subsidy must be taken advantage of....

Because storage is also not as expensive as it was, for example, 3 years ago. I’m getting the BYD high-voltage storage installed at 6.4 kW. With activation (500€) of the hybrid inverter, it’s 5,700€ without subsidy including installation. Online, this thing costs 4k€. In terms of specifications and especially efficiency, this unit is currently supposed to be the best on the market. Whether that’s really the case? No idea, but after some research it at least sounds that way.

For 5,700€ I currently get 16,300 kWh, so from my point of view it’s definitely worth considering.

For €5700 I currently get 16,300 kWh, so from my point of view it’s definitely worth considering.

Yes, but you must not forget the lost feed-in tariff.
I evaluated with Excel what I could have used myself this year with a 6 kWh battery. That’s almost 1000 kWh savings (in terms of self-consumption), but on the other hand there are about 200 kWh due to storage/charging losses. I get paid a good 11 cents and pay 26 cents per kWh. Assuming 30 cents, I therefore save 19 cents/kWh from the battery. Ergo:
(1000 kWh - 200 kWh) * €0.19 = €152/year.
The battery costs me, since I need additional stuff for SE, currently about €8000. So it would have amortized after 53 years...