[brucehoult]

In the summer the optimal angle where I live (35.5º S) is 12º. Panels lying flat on the lawn are losing only 2% from that. Just now, near the equinox, panels lying flat on the lawn lose around 18% at noon.

I'll find a way to prop them up at 50º for winter when the time comes for that (April or May), though that's for sunny conditions. In our typical overcast in winter flat on the ground is probably still fine to catch the most diffuse light. I'll experiment when the time comes.

[valenterry]

Right. I mentioned the suboptimal 60 degrees because many people hang it from the balcony (90 degrees) and the tilt it a bit, but usually not too much. From what I've seen 60 degrees seems like a good average number.

[brucehoult]

Yeah, in northern Germany vertical and 60º are pretty much equally good/bad in winter (75º would be ideal), but 60º will be getting 70% more power in summer than vertical, and is near ideal in spring/autumn.