Is a photovoltaic system also sensible in the West or East?

That helps you today if you sign the contract but then also nothing. Since the vast majority of people can do math, I don't really believe that the issue will catch on. You bind yourself unnecessarily to a provider. Make sure you use as much of your own electricity as possible and feed the rest in, that's it. No additional contracts, obligations, or provider lock-ins.

Of course nothing is "stored" there, but you get the electricity that you cannot use yourself during the day in summer back for free over the winter. That’s why it’s a kind of "virtual storage." Obviously, you are always tied to the electricity provider, but it’s better than nothing (the low feed-in tariff).

For what reason is a "cloud storage electricity contract" better for me AND the provider than if I feed the electricity myself and buy the electricity I need regularly from an electricity provider of my choice? I admit I didn’t even read the cloud contracts and I didn’t buy the photovoltaic system from providers who handed me corresponding flyers. For tax purposes, the cloud deals complicate the already absurd effort so much that standard software for photovoltaic tax is no longer sufficient.

Please forgive me if I don't fully get the financial models, but do I understand correctly that depending on the size, it can even be worthwhile if you fully finance it?

With east/west/south orientation, you get about 8500 kWh yield per year with 10 kWp (approx. 50 m²). That means €850 in sales if you don't use the electricity yourself. Through self-consumption, you can increase the annual income to maybe €1100/year. With rising electricity prices, even a bit more. Additional costs: - €50-100 insurance - €100 reserve for defects - €50 VAT on self-consumption in the first 5 years, afterwards 0€ - some degradation of the modules over time - possibly taxes, interest The system with 10 kWp should cost between €9000 and €13000 net. With that, you can calculate everything else yourself. The return is mainly shaped by the purchase price of the photovoltaic system, as you can see for example at guckguck. Without financing, I only break even after about 12 years.

For a still relatively short period, feed-in is still worthwhile. The date of the system registration counts. The feed-in tariff decreases every month. When registering a system under 10 kWp in September 2019, it was still 10.73 ct / kWh; in January 2020 it was 10.27 ct / kWh, already 5% less within 4 months. And it continues like this until there is no longer a legally fixed feed-in tariff. The prices for the systems continue to fall – as a private person you buy a heat pump installed in decent quality for about 1.00€. Now the calculation without subsidy with an electricity price of 30 ct per kWh:

Consumption in the house: 5000 kWh System (East-West): 6000 kWp Annual production: 5000 kWh Own consumption from the system: 3500 kWh

System costs: 6000€ Savings per own-consumed kWh: 20 ct Annual savings through own consumption: 3500 x 0.20 = 700€ Payback period < 9 years

When the feed-in tariff expires, the system sizing for own consumption is decisive. A much larger system only increases the proportion of own consumption to a very small extent and then becomes uneconomical. The share of own consumption can then only be increased with a storage solution. This is where hot water storage, batteries, etc. come into play.

If you buy the system above with battery storage, e.g. 2.4 kWh, then it costs around 7500€ including a different inverter. You increase own consumption to 3850 kWh (corresponds to about 150-180 charge cycles per year depending on degradation) System costs: 7500€ Savings per own-consumed kWh: 20 ct Annual savings through own consumption: 3850 x 0.20 = 770€ Payback period < 10 years

The “bets” on whether this pays off are the following assumptions: 1. How does the electricity price develop -> the higher the assumption, the more the battery pays off 2. How many charge cycles do I achieve per year -> some assume under 100, then it never pays off, others measure over 200 per year, which is probably the main point of contention 3. Assumption of the battery’s lifespan.

Those who do not see photovoltaics purely as a financial product but also as part of the design of the house can trade payback time for aesthetics and the value increase of the house. After all, façade and garden design are often chosen for aesthetics and not for a minimal budget. It is even said that there are people who buy cars without ever thinking about payback.

Long story short, as of today this works out wonderfully, you get the feed-in tariff guaranteed for 20 years. Besides, you won't get the small system for that money. The rest is pure speculation, no one knows what will come.

Oh come on. The Dax yields an average of 14% p.a. over such a period. You might as well pack up your solar panels on the cabin, which will later be hazardous waste, right away.

Photovoltaics are not profitable enough. It's fine that there are enthusiasts and people who find the technology cool. But from a return perspective, it doesn't pay off.

14% for the DAX was possible if you timed your entry well after the last crisis. The long-term average is 8%!
On top of that, you have price risk there. With photovoltaics, the income is guaranteed. Sure, there can be failures, but they can be insured for a small amount.

Photovoltaics are profitable!