9.2 kWP system - size of the battery storage?

I have a 13 kWp system and a 7.5 kWh storage. It works perfectly fine for me. From March onwards, I will supply myself almost completely independently. Choose the storage size according to your nightly consumption. The storage should also cover your household consumption at night during the summer months. Nothing more. Better put more on the roof; that way, your system will pay off faster. More storage won’t help you in summer either. ;) And then it costs too much in relation.

Thanks for the assessment. That sounds reasonable. Unfortunately, the catch is that I currently have no idea what range the nightly consumption will settle into :). But I will try to estimate it.

Edit: I would say or estimate that we are probably around 7.65 kWh at night (6:00 p.m. - 6:00 a.m.). Then the 6 kWh battery would probably be better suited.

Achieving 200 cycles with a heat pump and electric car is, in my opinion, very optimistic. Of course, if you charge the electric car from the storage (which would be absolute nonsense), it is of course achievable. Then your calculation is missing the feed-in tariff that you lose, 3-4 cents in taxes, and then on top of everything 20% storage losses.

But well, if you are aware that it doesn't pay off and you are not doing the environment any favors, I obviously have no objection if you buy a storage system. I would like to have one too... ;-) Then about the size: To get many cycles, two things have to come together. A consumption that (as already said by ) empties the storage in the summer AND a reasonable ratio of system size to storage size to fill it as often as possible during the year. Here, they say at least 2:1. 3:1 is better. So if you do not plan to increase your generator output, which I would very, very much recommend given your profile, a storage size of around 5 kW would be reasonable. With a little effort and luck, you can break even over its lifetime.

Backup power is a whole different topic with many variables.

as well as the wall box for the electric car.

You don't need storage for that - 80kWh car battery and under 10kW home battery don't match. Let the photovoltaic system charge the car completely on sunny days, that makes sense.

Edit: I would claim or estimate we are probably around 7.65 kWh at night (18:00 - 06:00). Then the 6 kWh battery would probably be more suitable.

Wow, what do you need that much electricity for? And how do you get the storage full again in winter?

You don't need storage for that - an 80kWh car battery and a house battery under 10kW don't match. Let the photovoltaic system charge the car completely on sunny days, that's sensible.

Wow, what do you need so much electricity for? And how do you refill the storage in winter?

The latter was a quick estimate of the annual consumption and the information in the grid that about 43% is used during that period. Yes, exactly the issue with winter and the large battery was also my initial concern.

In winter (Nov-Dec-Jan) the small battery is usually empty as well. The heat pump runs continuously, you want to use hot water and do washing/dishes during the day, and if the electric car is added, there is nothing left for a long time. I have just under 30 kWp on the roof and there is really very rarely anything left for the car. (On average over the three months I was able to charge 3 of the 27 produced kWh per day into the electric car. And it was almost daily connected to power from 2 pm.) From February it gets better again. Then the yield is sufficient again to cover the demand of about 20 km/day.

In short: nothing beats large, fully utilized roofs. I am currently planning to equip the south facade and the garage with 20-25 kWp.

...I have just under 30 kWp on the roof and there is really only very rarely anything left for the car. (On average over the three months, I was able to charge 3 out of 27 generated kWh per day into the e-car. And it was almost daily using electricity from 2 p.m. onwards) Starting in February, it will get better again. Then the yield will be completely sufficient for the demand of about 20 km/day. In short: nothing beats large, full roofs. I am currently planning to equip the south facade and the garage with 20-25 kWp.

Correct, no matter what others say. Currently, without hesitation, if possible, up to about 35 kWp on the roof. Those who want add a small battery for the electricity needed at night in the size of around 6 kWh. This can, with luck, break even late (if this battery was not bought at completely exaggerated but currently demanded prices). All of this goes to a large hybrid inverter and is throttled at 29.99 kWp because of the 70% rule. What I would give for a roof like that that would make this possible :oops: