Sunlight intensity does not vary between winter and summer, but allowance has to be made for cloud cover (but still get fine days in winter), panel tilt (some roofs would be normal to the sun in winter, others in summer).
Also do not confuse instantaneous illumination (kW and V) with aggregate insolation (kWhr), grids would be upset by too much kW and V, accountants are concerned with kWhr.
Belmont Solar City in Perth has a live display of the output from crystalline and thinfilm panels on their roof. One day I might plot out the ratio of output to see which does better when.
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