40, I have that one 150 watt Cfl in the reflector. i have 2 85 watt CFls. I have 3 45 watt CFls and several of those regular 27 watt CFls. however i don't think you have to have a 150 watt cfl in a reflector. basically after seedling stage i just surround the baby with 6500k lights of whatever wattage -just so it is right in the middle of those lights. i turn the plant as often as i can. like most CFL growers i am constaly moving lights around around: raising, lowering etc etc. i'm growing in soil, one plant in a 5 gallon bucket.