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The optimal direction for solar panels is due south (180° azimuth). Deviations of up to 45° east or west reduce yield by only about 5–10%. Even pure east- or west-facing roofs still achieve around 80% of the maximum possible output.
In Central Europe, the optimal tilt angle is 30–35°. Shallower angles (15–20°) generate more in summer, steeper ones (40–50°) more in winter. The annual difference between 20° and 40° is usually less than 5%.
In Germany, an optimally oriented solar system generates about 900–1,100 kWh per kWp per year. In southern Germany and Austria up to 1,200 kWh/kWp is possible, in Northern Europe rather 800–950 kWh/kWp. The exact value depends on location, roof orientation, tilt angle, and shading.
The self-sufficiency rate indicates what percentage of your own electricity consumption is covered directly by the solar system. Without storage it is typically 25–35%, with a battery 50–70%. The higher the self-consumption share, the more economical the system operates.
A battery storage system significantly increases self-consumption and self-sufficiency. For a typical 4-person household with a 5–10 kWp PV system and 5–10 kWh storage, the self-sufficiency rate rises from about 30% to 60–70%. Whether storage pays off financially depends on electricity prices, storage costs, and the feed-in tariff.