I picked a 'standard' CFL grow log at random as an example below. (Post your own or a grower you like and we shall examine it.) This grower is using over 30 watts per plant, but notice how only about 3% (I am guessing) of the light is actually hitting the leaves.

Attachment 280040

The cone of light on my plant is just slightly larger than the width of the leaves so the utilization is probably close to 75-80%. Again a guess.
RackitMan Reviewed by RackitMan on . My Single 3W LED A-Train Grow I see so many baby plants vegged under big HID lights or like 5-6 or more 23w or larger CLFs or a 90-120W LED, when that is hardly necessary. And then the same people talk about GPW... People did not believe the huge plant I vegged with a single 23w CFL, yet this is way more impressive. It is all about not wasting light. Here is my widdle 8" X 8" A-Train vegged under a single 3w cool white LED. Yes, one 3W light with nothing else. The hull wouldn't come off and it was nearly dead and I Rating: 5