i found this on the energy star site. i was woundering how many lumens i should have per plant use CFL lighting
To be honest, I've never worried about lumens. I try to have 100 actual watts per plant (or more) when using CFLs. Just stick to the general rule of thumb of 100w per plant and at least 50w for each additional plant and you will be ok.
It really depends on your needs. For CFLs I keep the plants small and prune the lower growth because they won't be seeing the light anyway. Don't think you can grow a 4 foot tall plant using the above suggestions. I would think more in terms of watts per square foot, not watt per plant. Trying to grow SOG with 25 plants in a 4x4 tray. Then using the above info, you need 2500 watts. Or 4 bigger plants on the same tray, then only 10,000 - 12,000 lumens. That's not gonna cut it. How much do you want to yield? How big is your space. There is no right answer. Use as much wattage as you can to get the best results possible.