OK, it seems like I'm not doing a great job of getting my point across.
I don't care how many g/W I'm getting and I don't care how many lights I run. This thread isn't about that.
The only question that we are concerned with here is how to get max yield from a given number of plants. My answer to this question is to grow the plants as wide as possible and use as much space as possible.
My reasoning is that bigger plants give larger yields and that the most productive phase is vegetation. See, if one is illegally growing, that person wants to keep electrical use low and maximize yield by Watt and/or by growing area. To do that you grow many small plants.
If one is doing a legal grow and needs to stay with say 24 plants, the game changes. What I am considering is a 2'X2' area per plant - so 12 plants would take up a 4'X12' area. The plants would be topped so they don't get too tall and they would be illuminated by 2 X 600W HPS on light rails. I love the light rails because if you turn the reflector perpendicular to the rail you get massive canopy penetration from the infinitely changing angle of the light.
Anyway, this method will give a 48 sq ft canopy as opposed to say a 12 sq ft canopy for small plants. That is 4 times the yield from the same number of plants. In exchange, this will cost about 3 X the electrical (given the larger veg light). And we will not lengthen our growing time either, because when on plant restrictions one must wait to take clones.
So, in the end, you get 4 times the yield, burn 3 times as much electricity, and you get rid of 3 weeks of down time. The only thing you need is a very large growing area and the ability to burn through a decent amount of electricity.