If your roof is so big that only a 7 kWp system fits on it, then yes, otherwise roof fully covered. 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, it costs 50-70€ per year. And make sure your private liability insurance covers photovoltaic as well. In case flying modules cause damage to others.
Run the heat pump on the house electricity. Saves the 2nd meter fee. General electricity you can get already for less than your 29ct. Since beginning of May I have e.g. 0.2293 €/kwh. Always switch providers and take bonuses.
Certainly more fits on it. But we would like to install only as much on the roof as we could theoretically consume ourselves. In my opinion, it makes no sense to fully cover the entire roof with photovoltaic if it is not clear what will happen to the feed-in tariff in the future.
After dealing a bit with the topic, I assume that in the long term feed-in will hardly be subsidized anymore and with technical development, complete self-consumption via storage is the future. Why should I then have more photovoltaic than necessary and, if in doubt, waste the overproduction? Better to install less photovoltaic now and retrofit a battery storage in a few years when they are more powerful and cheaper.
As already written here, the electricity price strongly depends on the supply region. There are certainly offers for 24-25 cents per kWh, but I prefer to calculate conservatively with 29 cents...
The 420 EUR p.a. consist of maintenance/wear, cleaning, and insurance.
It really isn’t that difficult, you just have to calculate what the system brings you, meaning self-consumption + feed-in tariff, and then compare it to the investment. You mix too many things here, your maintenance costs are also way too high.
Example:
10 kWp system costs 12,500€
it produces your 10,000 kWh per year.
of that 6500 kWh feed-in and 3500 kWh self-consumption.
6500kWh x 9.875 cents (my own tariff) = ~650€ p.a. 3500kWh x 25.07 cents (my electricity costs) = ~875€ p.a.
= ~1525€ p.a.
You can then also offset your few pennies in interest and, if you want, 150€ for maintenance, repair, and insurance. I leave the conclusions to you.
Your calculation is certainly correct if I want to know when my photovoltaic system pays off. But I am more interested in the economic advantage compared to the usual external electricity supply.
I don’t believe in the 8 cents. On the one hand, we are already very close to 8,x today; on the other hand, the development of the Renewable Energy Act after the 52GW cap is completely open. Personally, I consider it absolutely impossible that the subsidy will rise again. What is being discussed are rather different models with significantly lower feed-in tariffs (goal: self-consumption systems).
Conclusion: profitability calculations for 2021 are a waste of time, and current offers won’t be valid anymore by then anyway.
I share that opinion, see above.
Therefore, my strategy would be: photovoltaic system calculated for self-consumption now on the roof and take the feed-in tariff in the first years. As soon as the investment in a storage system pays off, buy one and celebrate independence from external energy. Is this thought completely wrong?
But we already have to decide for or against a photovoltaic system now. The house concept is already or will be finalized by the end of the year.