What I mean by adding lumens for example: Think of the light that comes out of the bulb like an upside down v. If you put three bulbs together, it overlaps. My growbox is definatly more bright with more bulbs even if they are placed close together; but, I'm sure that it isn't nearly as effective as the same wattage coming from one bulb. I find it very hard to believe that the amount of lumens coming from 3 bulbs is the exactly the same as one bulb of the same wattage.