I run 2 GLO T5 36" fixtures w/ 4 39w bulbs. I don't have a meter or any official way to test the light difference from my previous 192w cfl setup, but you can't really compare the 2. Growth is significantly better, and the color is out of this world. Previously I was rinning only one of these, and it still destroyed the CFL. These are the single reflector for 2 bulbs that everyone says inst so good, but from my research a single reflector per bulb although losing some of light, extends the life of the bulb by 2 to 4 months. Random web fact, are they true who knows, but I can tell you from experience, cheap t5 setup cannot be compared with the cfl lighting. T5 all the way.