i run a 600 watt hps and for the winter i grew indoors, i grew in a closet about 2 and ahalf feet wide and 4 feet long and 8 ft tall and in some areas it was only 4 feet tall cuz the rof is slanted, i kept my room in the high 70's at all times and i used a 2 small fans inside the close one blowin on top of the plants and on the bulb a bit and the other small one below blowing up the skirts then hitting the bulb, also i used a 24 inch house fan to supply cool fresh air into the room. i also was able to keep the the light 15 inches away from the tops safely. i had a inline fan for it but these three fans are much cheaper to run and to buy. and for me works just the same in a way.