I'd say "most" that we see around here are 20 acres or less.
Recently there have been a couple larger sites started.

But, I do have a question. We receive letters here occasionally by companies searching for solar sites. They want to "lease your 80 acres...." for a solar site. But, the actual panel site may only be 10 acres. So, do they pay only on the 10 acres they took out of the 80 acre field? Or do they pay you on the whole 80?