Keep seeing the question "how many do I use"??
The usual answer (and is right-- but not entirely helpful) As Many as You Can!
Often called "energy saving bulbs" CFL's use less wattage, put out little heat and are easy to find... but are NOT as efficient as HPS/MH... BUT ARE better than traditional "tube" flourescents...AND you CAN get a decent grow from them IF you use enough!
Heres a pretty easy way to figure the bare minimum in CFLs for your grow--start to finish....
never use any output smaller than 100w...
it's a waste of $$ and not efficient (uless ya allready have em-- then do the math and use the equivelent!)
HERE YA GO:
sprouts to 3 leafers--2 for up to 6 sprouts
3 leafers till 10-12 inches--1 per plant
10-12 inches till they go 12/12-- 2 per plant
12/12 till harvest-- 3 per plant, additional side/back lighting helpful
OR get the BIG CFL's That are 100-150w useage 500-600w output in a decent reflecter (These do NOT fit in household or regular fixtures!
You MUST get the special ones made just for them!) ...
and use 1 for every plant... pricey tho---
Below you can see some grows using CFL's and CFL's with Floro tubes ... they can work if ya use enough of em!