Photovoltaic system: Costs, saving potential? - Experiences?

You don’t do that through the general contractor but look for the best offer yourself. In January, we paid a flat €12,000 gross for 9.2 kWp including HomeManger.

That works out even worse, because although we then have more panels on the roof, our self-consumption rate goes down. It’s only really profitable if you use as much of the electricity yourself as possible and feed in little.
But that’s not so easy, unless you consider a combined heat and power plant/battery, but then it becomes disproportionately much more expensive again, it’s not worth it at all.

Unfortunately, that is not true.

- first error already in household electricity consumption. Where are 4000+2800+400 = 8000?

My mistake, I was juggling the numbers a bit in Excel and added a buffer on top (I assumed 400 for air conditioning was a bit underestimated). But I didn’t update the basis of my assumption above, it was just a mental note. The calculation is only done with the value stated below (8000).

- electricity price 2020 is supposed to be 0.26 cents, four columns to the right it says 0.24 price per kWh. Huh?

The beige highlighted was a specific offer I had calculated. The "electricity price approx." is calculated from the data in the offer and takes the basic monthly fee into account. 24 is only the price per kWh. My total costs consist of both per kWh price and basic fee. Therefore, this must be considered.

- acquisition cost 9280€ for 4.2 kWp absolutely overpriced (biggest wrong assumption in the calculation imo). The system should cost around 4600-4800€ net. Or is a storage system counted in that ruins the balance?

No, that is a gross price, but as it is. It was already included in the first offer from the general contractor and at that time we were very afraid and wanted everything from one source.

- The photovoltaic system is simply too small for household consumption. The share of self-consumption is likely relatively high, a storage system particularly uneconomical, if pursued.

Not planned, we have a storage system in other calculations of the table, but as you say, that is even more uneconomical.

- All taxes were forgotten. In case of self-consumption, the VAT is missing, which negatively affects profitability. On the other hand, this applies only for 5 years (then small business regulation). Also working in the other direction is the depreciation, which is ignored (especially with the high system price)

It also says in the initial post that I did not consider taxes because I didn’t know how that fits into the Excel sheet. Especially since I didn’t know that VAT is charged for self-consumption? I thought only for feed-in?

Actually, I didn’t know that VAT applies to self-consumption? I thought it was only for feed-in?

Even more is due for self-consumption. You also have to report the monetary benefit you have in the income/expenditure statement and pay tax on the profit.

But it doesn’t help; the mistake lies in the acquisition itself. But everyone else has already said that. Then your calculation would also look much nicer.

For self-consumption, even more applies. You also have to include the monetary benefit you have in the income/expenditure statement and pay tax on the profit.

But it doesn't help, the mistake lies in the acquisition itself. But everyone else has already said that. Then your calculation would also look much nicer.

That's true. But now the horse has bolted. We are still looking forward to the photovoltaic system.
At that time, the decision was made from a different perspective. Now, half a year later, we know much more.
We are here in the forum, have more experience with the construction situation. At the beginning, we were completely focused on getting absolutely EVERYTHING from one source, since we are very far from the craft professionally.

But is it really realistic to get a 4.2 kWp system, complete with inverter and all installations for under €5,000 gross?
At the time, I had seen few real "offers," but what one read on the internet regarding costs rather corresponded to our offer from the general contractor, not half of that.

But is it really realistic to get a 4.2 kWp system, complete with inverter and all installations, for under €5000 gross?

No, it is not. The prices are always net, since you only pay net and reclaim the VAT. However, for this system size (which hardly anyone does because the installation costs are disproportionately high), €1850 is clearly too high. For your €7250 net, a system in the size of about 5.5–6 kWp should be feasible.

7250€ net should rather bring 6.6 kWp. I wouldn’t pay more than 1100€ net anymore, even for "smaller" systems. Of course, it always depends on the components, LG is just more expensive than JA. Whether it’s worth it is another question ...