Always seemed to make the most sense to me to express as (dry weight/wattage)/time.
Using multiple large HID lights, consensus target was .6gram/watt/month.

If you did 6+ z , that's bout 182 grams, or .728 grams/watt (figured only using the 250 hps)

(.728g/watt)/4 months total =(.182g/wt)/month.

Keep in mind, though, that this formula doesn't allow for the lower efficiencies of floros and smaller HID lights. It really doesn't allow for veg time, and assumes unlimited access to cuttings. It's really a metric for flower room eff, not eff of total grow system. The assumptions are based on commercial production.

If you started from seed, and brought in 182g in 8sq' with that lighting, I'm gonna say you did pretty damned well.

Are you happy with it? I would be. That's what matters. Don't go nuts chasing #'s.

Also, keep in mind that differant genetics yeild differantly. The above goal of (.6g/w)/m assumes the use of high yeild commercial genetics. It's not too tough to hit running PP or Critical Mass in hydro w/ c02 and a/c- but you'd never get close running a white, even w/ all the bells and whistles.

To figure out sys efficiency, you have to first state a unit of output measure. Then you can start doing input/output ratios. The (g/w)/m metric only refers to dry weight at the end of the day- not what you learned, how much fun you had, how it feels to break out a stick of your own and level the room, the joy of sticking your head in the garden- all the intangiables.

So it sounds like ya did real well.

" I'm gonna give it a nine, Casey...
It's got a good beat and I can dance to it!"