would anyone care to speculate as to numbers? as far as i can figure, a 150 HPS puts out 50,000 or so lumens, where as a 42w CFL puts out about 2600. Mathamatically, if i could have 19 or so of those little, cool suckers nestled right up near all of the photoreceptive areas of the plant in question. This of course doesen't even take into account that the HID will degrade much faster than the CFLs will, or CFL of the 55w-200w range, which should produce more lumen per watt. one thing i have not been able to dig up however, is the PAR values for CFLs, thus i cannot make an accurate comparison mathamatically. i am just wondering if anyone has any practical evidence to support these theorys a little more than the anecdotal "i had a plant under CFLs, it was doing ok, but man what a difference that HID made!!!1!11!1"