I have to argue this point a little.... Actually itis quite proven, not only be research but also by visible testing that a single light on a rail will yield much better on average than 2 stationary lights of the same wattage or lower, obviously in certain size rooms, as a single like trying to cover say 20 feet would be useless. Why is this true? Well you see with the light moving back and forth across your ceiling and setup to run as much of the grow room as possible, almost all parts of the plants get light and get light from different angles. A light rail also stops hot spots in a grow room.
I myself was very skeptical on a light rail when I first starting researching them, I then began talking to people, hydro stores, hydro growers, online growers etc.. and come to find a very interesting growing method. Largest light rail grow that actually saw true gain from a light rail over multiple lights was 12 feet, with most people having 10' or under lengths with light rails. I actually got to see a local hydro store do a test, I kinda requested it. He grew 4 tomatoes in each of his bays, placing them in a line roughly 2' apart, one had 2 600w hps and the other had a single 600hps on a light rail, each bay was roughly 8'x4'x10' LxWxH. All 4 in the room with a single light on a rail were very much larger, especially in width, when it came time for flowering, the plants in the light rail room had almost twice the amount of flowering sites. The end result was the tomato plants in the light rail room finished with several more tomatoes and all the tomatoes between the two rooms were about the same size, though the largest of the tomatoes did come from the light rail room.
The movement of the light lets the light cover areas of a plant that would normally only get partial light or maybe even almost none. it is also proven that if you have a single light sytem and move the light manually 6" in either direction every other day your grow will be much bigger and fuller than a stand still.
