This is a question that AFOAF has also asked. and so far, the answers he has recieved are
"Sugars", ie, even white death. but brown sugar, mole-asses, and he heard today, from dispensary dude, JUICES. Yes, fruit juices not from concentrate. As soon as dude said it, AFOAF was like "Fuck yeah!"
"Watts", but they have 2k in a 4'X8'...so thats not it, with them
"Strain"..Sure, makes sense. But, when AFOAF asked for advice on a high yielding strain for heavy pain, he was told, "Ahhh... most of the good pain meds, like the OG's, arent known for their heavy yield", which at least made AFOAF somewhat comforted in that the hella low yield of some strains relative to the yield of the others made a bit more sense"
another friend of a friend of a friend mentioned airflow, both in and out.
hope these help a bit, and any other tips are more than welcome
namaste