> How can it be 50% when the sun is beyond the horizon for 17 hours straight?!

50% of the average. The average being a day with something like 12 hours of sunlight. Sorry to be unclear.

> I see what you mean, but plants optimize for electricity value, not rough output, and electricity is more expensive in winter, if they could get good yields at that period, they would actually make more money than the one they get by selling excess electricity in summer…

One important factor is that they're not optimizing for power per panel. Panels are pretty cheap, and filling the land with panels makes sense as an overall decision.

Let me reframe things. For a commercial plant it's not that they could get significantly more power in deep winter, it's that they could get the same power with 20% as many panels. But spreading panels out that far would be worse the rest of the year.

Many home installs can get that "spreading" for free.

So to redo my claim from earlier, if there was a magic button to put 50 feet between each row of panels with no downside, I strongly bet commercial installs would pay to press it. And it should take the winter output up from "useless" to "bad".

It's possible I'm still severely underestimating the clouds. But when there is light, there's this interesting advantage small/widely-spaced installs get in winter. Or rather, they have a much smaller disadvantage.