This is something of a mess writing wise, I'm stoned and don't have anyone handy to edit it. Theres a nightmare run on sentence with a billion parentheticals because I returned to revise my thoughts. I'll try to edit it later but her it is for now because there's been a bunch of posts in here since yesterday.
Skunkdoc the thing about vertical setups is they almost always take up a much larger footprint than the theoretical canopy. I have a friend who is running a v-scrog in a room that's 5x7x7 where the screens are ~2' from the bulb and I think are 42" high. Or maybe the circle is a 42" diameter. The point is he managed to get about 38sqft of illuminated canopy with a single 1k bulb in a room that's only 35 sqft. It's jammed so tight he had to build a lazy susan to get access to the plants. For a single light grow trying to produce for yourself without spending a fortune on electricity and more space than light this is really high up there in terms of grams of bud produced of a given strain per kW of energy used. He also does a long veg with ~100W of fluoro to build a good root system shape the plant for how he wants it to go into a perpetual setup but 16 weeks of 100W of fluoro is the same as 4 weeks with a 400W HID and plants in veg are a lot smaller than plants in flower so keeping them around to veg a good long while and be monsters works for him. I think his state also doesn't consider vegging plants or has a higher limit for them so having a bunch around for a long time is no issue. His grow is very efficient to him which is what matters in the end.
The variables with efficiency are how much electricity you use (remember lights aren't the only things), money spent (water, nutes, rent of a grow facility, paying your full time security guards who rape intruders with hot cooltubes, whatever your operating costs are), time (should a sativa that takes 16 weeks to flower and yields half as much per crop be considered 1/4 as efficient as an 8 week hybrid that twice as much per crop?), space, plant count (if it's not an issue it's really hard to beat some kind of SOG because all you need to do for veg is root the clones, you have fans in flower that use more energy than those lights), strain, nutrient use and that's just off the top of my head. You have to weigh each of them to decide how you want to tune your grow. In the example above if initial startup and running costs weren't an issue (ie a large grow expanding) then make sure you have the cooling and run 80+W/sqft with CO2. SOG or ScrOG to fill the canopy depending on plant count. If you can pack the canopy with even buds with room for airflow you will get the most bud from that flowering cycle.
My g/W from my last cycle was only about 0.6g/W, but I'm in a 2x2x4 space and beat a half pound, that's ~600g/m^2 for our metric friends. Most important to me I have enough bud I could work on making seeds and hunting for new moms with this run.
