I have a 400watt hps with an air cooled hood and I'm flowering 4 plants right now too. I use it in a 3x3 4ft tall space and I am very happy with it. I live in a 1 bedroom apartment so my ballast is outside my bedroom and I exhaust outside of my bedroom, if I didn't do this it would be too hot to run it. I also have central AC which is a must. heat control should be your biggest consideration when looking into a HID system!