Back to the question, I think you have to go by the number of lumens for an accurate comparison. I don't remember the numbers but I do know that an HPS has a much higher number of lumens per watt. That's the key. A little searching will answer your question. It's here. But look at lumens.
qdavid Reviewed by qdavid on . CFL Light Intensity Question... Does anyone know the optimum positioning of a CFL. What I mean is, does a CFL's light intensity radiate parallel to the bulb (inline with the coil) or perpendicular to the coil. I don't know exactly how to explain my question, but I do not know if I should align my bulbs so that they point at my plants, downward vertically, or if they should be aligned so that they point outward, horizontally. Does anyone know ? Rating: 5