yes yes lets devolve into the "lumens don't add" act.
After reading this thread I have no idea what anyone is after...
More watts is more yield plain and simple. More watts, tends to lend to a higher intensity- which means, how much, how many umols of lights, are shooting out of a particular point... the more the better, a la HID.
HIDs are pretty crazy though... and inefficient, oh, and put out too much unusable, unphotosynthesizeable light. which means its wasted electricity and therefore comes back at you in the form of heat.
Lumens don't exactly add, yes, If you have one point of light, putting out so many lumens, adding another point of light proximally of the same intensity will give a higher rating on a meter... but the factor isn't exactly addition. its lower than that, and at a point, adding more points of equally intense radiation won't help the rating rise above that of the individual bulbs...
but more watts burned will help a plant.
As for spectrum specific light sources... I don't think there is anything other than anecdotal observations on the correlation between spectrum/watt and parity to hids... meaning, all red at 100 watts obviously is better than 100 watts of warm flourescent, or HID for that matter, but not many times better. its not magic, cause its not any more intense, its not any more light, umols, einsteins...
So still its the wattage that matters most.
The intensity, the initial lumens, is what really counts, you must hit the plant hard to even try and mimic the sun. and the sun hits fucking hard. again, more watts lends to this. More watts in a smaller package means this.
So in sumation, low intensity, wider points using higher wattages not as good as similar watts in a more effecient, more concentrated package... I'm thinking good leds and hids, although hids can be placed feet away, and leds should be inches away... A testament to the initial lumens and the lower lumens per watt of leds, and they're lower power handling capabilities.
sigh.
this argument is non existent.
my led, uvb cfl grow is successful. I think I will get close to a half pound from like 900 watts... but i really dont know yet. I mean, gram per watt is standard.
You do that kind of growing at about 60 watts per square foot. No matter what source, I think this number is a good guidline to go by to be a standard grower... below this there is no better upgrade for your garden than being able to handle more watts, more intensity, more initial lumens... more PAR, umols or micro einsteins of light.
So, the minimum is 60 watts per foot if you want to be responsible, no matter which package you choose. (thats a 1000 on a 4x4 table, and a 600 on 3x3)