Photovoltaic system: Costs, saving potential? - Experiences?

the calculation is complete nonsense

Complete nonsense.

Why so unfriendly?

What is unfriendly about the word Unfug?

Thank you for your reply.

...
Your calculations are roughly not wrong but quite incomplete and therefore also not realistic.
You still have to consider at least 2 factors:
...
What is certainly the case: A photovoltaic system is in most cases a very profitable investment.

I would also emphasize that. But it is certain that most solar installers currently
make offers with 9.9KWp and battery for about 20K net,
which is unfortunately often "nonsensical."

Currently, I have seen 5 offers ranging from completely overpriced to
expensive and *nonsensical (*not suitable for needs and situation).
One would have been acceptable, but it was not "optimal."

The advice to look around the appropriate forum has already been given. And that should be taken seriously. The 20 - 30K that may then be invested almost always pays off (provided the system was not purchased at a completely overprice).

Rule 1: Roof full
Rule 2: Roof full
Rule 3: Battery is a matter of preference, but can be justified with the arguments of autonomy and ecology.

Try to understand what photovoltaics can do and what is not possible.

If storage, then rule of thumb: 2x more KWp on the roof than storage in KWh.

Everyone sets different priorities. A purely economic consideration is certainly permissible, but is that what you want?

Think about what a total concept with a BEV in connection with 25KWp + about 16KWh battery might bring? Tax-wise, ecologically, economically?

(with 25KWp you will usually also have to cover the "worse" north side, with inclination of 35° and northeast orientation PVGIS gives about 65% of southwest as a result, which also makes the photovoltaic yield more evenly distributed over the day and cancels out the 50% regulation (with battery!))

P.S. For a single-family house only 2600KWh for the air-water heat pump seems very low to me, but it can work. The rest of the electricity consumption also seems very low to me.

Try it with self-consumption + feed-in tariff

I have now read a bit deeper and understood that we are currently in transition... away from feed-in and towards almost complete self-consumption with the help of a storage system.

Currently, however, battery storage systems are still probably too expensive, so feed-in is still (and in the medium term) more economical.

Our initial consideration was to become completely independent from external energy supply. But that may only be possible in the next few years -> topic of retrofitting battery storage.

1. Your load curve of electricity consumption: When in the year do you need more electricity and when do you have more electricity yield from your photovoltaic system? I have not yet seen a household where electricity consumption in winter is not significantly higher than in summer. In contrast, the yield from the photovoltaic system is significantly higher in summer than in winter. As a result, you will not be able to supply yourself with electricity in winter and will have overproduction in summer. And that brings us to

2. For the overproduction of your electricity, you receive a feed-in tariff of - let's say 9ct/kWh. This gives you income in summer.

The offer of 13k for a 6.83kWp system seems high. What is included in that? Others here in the forum have had significantly larger systems installed for the same money. Also, the electricity price including meter seems somewhat high to me - especially since you can surely get a heat pump tariff for the heat pump that is worthwhile.

What is certainly true: A photovoltaic system is in most cases a very profitable investment.

We don’t have any offer yet. I just wanted to roughly estimate what it would mean financially for us to integrate a photovoltaic system into the overall concept. The 13,000 EUR are from the internet and I believe inclusive of installation and possibly battery storage (?).

After renewed research, I would rather assume a 7 kWp system for 8,500 EUR (including installation). More realistic?

P.S. for a single-family house only 2,600 kWh for the air-water heat pump seems set very low to me, but it can work. The rest of the electricity consumption also seems very low to me.

Thanks for your suggestion. I picked that up and set it at 6,000 kWh (currently, the two of us consume 2,600 kWh general electricity without heat pump).

I would correct my calculation according to your suggestions as follows:

Parameters:
- 7 kWp photovoltaic system for 8,500 EUR incl. installation (= share annuity house bank loan: 26 EUR)
- Maintenance costs 420 EUR p.a.
- Production of the photovoltaic system: 850 kWh/kWp p.a. = 5,950 kWh p.a.
- Total consumption 6,000 kWh; thereof 2,600 kWh heat pump
- calculated self-consumption rate: 45 %
- feed-in tariff: 8 cents/kWh (since completion of single-family house planned for 11/2021)
- heat pump electricity tariff: basic price 90 EUR/p.a.; 20 cents/kWh
- general electricity tariff: basic price 150 EUR/p.a.; 29 cents/kWh
- tax considerations initially neglected

Total costs with photovoltaic system p.a.:
- Loan annuity 312 EUR
- Maintenance costs 420 EUR
- Heat pump electricity tariff: 90 EUR + 413 EUR (2,600 kWh - 536 kWh* x 0.20 EUR)
- General electricity tariff: 150 EUR + 365 EUR (3,400 kWh - 2,142 kWh* x 0.29 EUR)

*Photovoltaic system production 5,950 kWh
thereof feed-in: 55% = 3,273 kWh
thereof own consumption: 45 % = 2,678 kWh (thereof 20 % for heat pump; 80 % general electricity)

= 1,750 EUR minus 262 EUR (feed-in tariff 3,273 x 8 cents) = 1,488 EUR (124 EUR p.m.)

Total costs without photovoltaic system p.a.:
- Heat pump electricity tariff: 90 EUR + 520 EUR (2,600 kWh x 0.20 EUR)
- General electricity tariff: 150 EUR + 986 EUR (3,400 kWh x 0.29 EUR)

= 1,746 EUR (146 EUR p.m.)

Advantage of the photovoltaic system:
258 EUR p.a. or 22 EUR p.m.

If your roof is so big that only a 7 kWp system fits on it, then yes, otherwise the roof is full. But this has already been said here. Your roof earns money. The larger the system, the lower the price per kWp. Maintenance costs of €420/year are, in my opinion, set way too high. What do you want to maintain? Don’t forget a photovoltaic insurance, which costs €50-70 per year. And make sure your private liability insurance covers photovoltaics in case flying modules cause damage to others.

Run the heat pump on the house electricity. Saves the second meter fee. General electricity is also available for less than your 29ct. Since the beginning of May, for example, I pay €0.2293/kWh. Always switch providers and take bonuses.