Evaluation of Photovoltaic Offer and Components

As an example, my system (7.2 kWp) with a 10 kW battery.

Energy yield on 29.04.2023 8.52 kWh
Consumption 9.73 kWh
Grid feed-in 0.10 kWh

Energy yield on 06.05.2023 19.65 kWh
Consumption 9.22 kWh
Grid feed-in 0.11 kWh

Construction costs 11,000 euros or 1527 euros per kWp, however including the battery.

As you can see, no grid feed-in thanks to the battery. And the battery also gets me through 1 or 2 rainy days. I only plan the water heater with a timer so that it heats up only between 10 a.m. and 3 p.m.

I don’t know if it makes much sense to fill the roof completely and just not buy a battery. Even if many do it that way, it would not have been an option for me although I have several hundred square meters of space.

And if there is snow on your system in winter, then it doesn’t matter how big or how expensive a system was. The result is always close to zero!

I don't know if it makes much sense to fully cover the roof and just not buy a storage system. Even though many do it that way, it wouldn't have been an option for me even though I have several hundred square meters of space.

You can tell that you don't know that.
I am not against storage systems per se, but you can calculate it. Just because the storage system (possibly) pays off does not mean that investing the same amount of money that the storage system cost in more photovoltaic modules wouldn't have been even more lucrative.
Personally, I don't find profit maximization in this area very important, we also take the storage system because it is an ideological decision and it at least pays for itself within the warranty period.

Nevertheless, you can calculate all of that. And I would not recommend a storage system to anyone if the storage system does not pay off within the warranty period. And when I see offers where a 7kWh storage system costs over 7,000€, then that is a purchase with high risk. The chance that the storage system will break down before you have recouped the purchase costs is not exactly small.

Basically, I am with Kati, but how can the decision for a storage be ideological in nature?

Basically, I agree with Kati, but how can the decision for a storage system be ideological in nature?

I don’t know if I’m wired differently, but I like the feeling of consuming as much electricity as possible from my own roof myself. I even like that better than making maximum profit from my capital. If I wanted that, I would actually have to ditch the storage system and find space for more modules, feed the surplus into the grid, and then try to shift our consumption as much as possible into the sun hours. It somehow feels better to channel from the roof into my storage and from the storage into my PC than to buy green electricity from the grid. The one from my roof even feels "greener" than the one from the hydroelectric power plant. Maybe ideological is the wrong term and "crazy idea" fits better. ;)

Yes OK, it is often more a kind of selfishness or simply fun. Because a storage does not help the environment at all in the first place.

Because a storage system doesn't help the environment at first.

Yes and no ... of course, the storage system consumes production resources. On the other hand, if a household with storage manages to optimize its own electricity consumption in such a way that external consumption is minimized, then this helps with the current grid capacities and also avoids one or another kWh that would otherwise have to be generated with quickly adjustable gas or coal power plants. Or on sunny and/or windy days, it also helps avoid one or another shutdown of externally switchable photovoltaic/wind systems.