Photovoltaic system 120 sqm living area - cover the entire roof?

Hello everyone,

I am currently inquiring about an expansion of our planned photovoltaic system.

The total power in the standard version is 3.75 kWp. I have been thinking about increasing it to 5 kWp.

Now I am looking here in the forum and see many examples with 10 kWp and more.

Of course, it makes sense to cover the roof as fully as possible, but the price does play a role for us.

There are two of us on 120 sqm of living space.

What are your experiences to achieve the best possible price-performance ratio?

From an economic perspective: You have to calculate to what extent feeding in is profitable for you and how much more you can use in your house. Many here still received a no-brainer compensation. Other goals can be achieving a particularly high degree of self-sufficiency or contributing to CO2 reduction or the acquisition of further key consumers... Ultimately, your decision depends on your goals.

Price-performance ratio: The larger, the cheaper the kWp.
In addition, you increase your autonomy.

3.75 kWp sounds very low. The fixed costs for the inverter, connection, etc. will probably be quite high. I would personally do at least 5-6 kWp so that it is economically somewhat worthwhile and you still produce some own energy outside of midsummer.

Ok, thanks a lot already. Yes, that sounds reasonable. We have our roof on the south side and no windows on it. That almost suggests itself.

The expensive part seems to me, after a first research, to be mainly the battery. Is there a rough rule of thumb for the ratio of modules to battery?

I tend to double the modules then. Currently, it would be a 5 kWh battery (according to the prefab house standard). The next steps are 7.5 and 10 kWh.

Photovoltaics are best as large as possible for the environment!

Are you building KFW40+ or similar, where a storage system is required?
If yes, then as small as possible. If no, then omit it.
At least that is what makes the most sense (for the environment and wallet) in a typical single-family house.
In special cases with specific consumers, it may look different.