The installed nominal output for the individual figures indicated cannot be taken to represent the overall output of the system in question. For instance, if a ground-mounted array is connected to the grid in sections, then each section reported on a different day is a registered at the Network Agency as a separate system on those different days, so that the overall plant's nominal output cannot be gathered from the lists.
(Die gemeldete installierte Nennleistung der einzelnen Datenmeldungen ist nicht mit der Gesamtleistung der Anlage gleichzusetzen. Wenn beispielsweise eine Freiflächenanlage Zug um Zug in Betrieb genommen wird, erfolgen die Datenmeldungen an die Bundesnetzagentur in der Regel sukzessive und gehen an verschiedenen Tagen ein, die installierte Nennleistung der gesamten Anlage kann nicht den Listen entnommen werden.)
In layman's terms, a 240 kW system might actually be connected to the grid in four segments of 60 kW, so that single array would appear as four 60 kW systems, not one 240 kW system.
My reader says that this report, which has apparently not been translated though a press release was published in English, contains the adjusted figures, though if you take a look at the bottom of page 13, you will see that the report contains a similar caveat for wind power, though I could not find an indication of the same for solar.
Anyway, assuming that the figures were adjusted for solar, the report from July 2009 unfortunately only applies to figures at the end of 2007, but they clearly indicate the following figures (also in the chart on page 13) of total power by arrays size:
- 2,591 kW in arrays smaller than 30 kW
- 686 kW in arrays from 30 to 100 kW
- 281 kW in arrays from 100 to 500 kW
- 419 kW in arrays larger than 500 kW
Clearly, the smallest category predominates, though a 30 kW array is not necessarily that small -- you would probably only have three or four on your average home roof, and even a large Black Forest farmhouse is going to max out around that size (panels used to produce around 150 W are now closer to 200, so you would still need around roughly 150 of these things to get 30 kW).
At any rate, it certainly seems hard to get the average array size. If anyone has any other sources, please let me know.