Just finished a T5 grow from veg to harvest. The T5's (4ft, 8 bulb) definitely run cooler than the HPS setups. The only problem is that they just can't penetrate the canopy of a good batch of indicas. I had to constantly move fan leaves around so the buds could be exposed. I even had to turn the plants each day. I also added 2 additional single T5 4ft fixtures on the sides. Overall, I yielded 7.5 oz for 5 plants that did 1 month veg, 2 months flower. Not bad but nothing to compare it to.