ᐅ Photovoltaic System for 120 sqm of Living Space – Should the Entire Roof Be Covered?

Hello everyone,

I am currently looking into expanding our planned photovoltaic system.

The standard total capacity is 3.75 kWp. I have been considering upgrading it to 5 kWp.

Now, browsing through the forum, I see many examples with 10 kWp and more.

Of course, it makes sense to cover the roof as much as possible, but the price is an important factor for us.

There are two of us living in a 120 sqm (1292 sq ft) home.

What are your experiences with achieving the best possible balance between cost and performance?

From an economic perspective: You need to calculate to what extent feed-in remuneration is profitable for you and how much more you can use in your house. Many people here still received a no-brainer tariff.
Other goals can be achieving a particularly high degree of self-sufficiency, contributing to CO2 reduction, or acquiring additional major consumers... Ultimately, your decision depends on your personal goals.

Price-performance ratio: The larger the system, the lower the cost per kWp.
Additionally, you increase your energy self-sufficiency.

3.75 kWp sounds quite low. The fixed costs for the inverter, connection, etc. will probably be relatively high.

Personally, I would recommend at least 5-6 kWp to make it economically worthwhile and to still produce some of your own energy outside of peak summer.

Ok, thanks very much in advance.
Yes, that sounds reasonable.
Our roof is on the south side and there are no windows on it. That seems ideal.

From my initial research, the most expensive part appears to be the storage system. Is there a general rule of thumb for the ratio between modules and storage?

I am therefore leaning towards doubling the number of modules. Currently, it would be a 5 kWh storage system (corresponding to the standard for prefabricated houses). The next steps would be 7.5 and 10 kWh.

Photovoltaic systems are best installed as large as possible for the environment!

Are you building a KFW40+ or similar standard where a battery storage system is required?
If yes, then keep it as small as possible. If not, then omit it.
At least for typical single-family homes, this makes the most sense (both environmentally and financially).
In special cases with specific energy consumers, the situation may be different.