roseman posted this on my old site as part of a CLF tutorial, i take no credit for it... just passing on the information hope it helps someone.
TOKE OUT
Look at a lumen/watt ration of various CFL's. The higher the wattage of CFLs, the lower the lumen/watt ratio. This chart was submitted by Jerry Garcia, a grow buddy from another grow site, and edited for typos.
For example...
the 200w listed at 9250 lumens for a lumens/watt ratio of 9250/200=46.25
the 150w is listed at 7500 lumens for a l/w ratio of 7500/150=50
the 125w is listed at 6500 lumens for a l/w ratio of 6500/125=52
the 42w are listed for 2700 lumens, l/w ratio of 2700/42=64.28
I have some 26w that give off 1700 lumens for a l/w ratio of 1700/26=65.38
GE lists some 13w that give off 825 lumens for a l/w ratio of 825/13=63.46
So, according to these numbers the most efficient bulbs for growing are the 26w that emit 1700 lumens. If you used 8 26w bulbs (208 watts total) you'd be getting 13,600 lumens...4,350 more lumens than a single 200 watt CFL. AND the eight 26 watt bulbs would cost less than the one 200 watt bulb.
I suppose you need to purchase more sockets and cords and things to support 8 bulbs, but in the long run, more lower watt CFLs seem like the way to go.