Hey Total NOOB...Mutt and Hick are of course right on with their answers, so your definitely headed in the right direction...IMHO I would forget about anything smaller than a 400w MH or HPS, If your going to veg and flower in one box and not have a perpetual grow system you could also get a dual ballast light which provides the ability to switch from MH for veg and HPS for flower. If you have the funds this is the way to go. Also IMHO for a box that size you are going to need more than one fan, most likely flow thru ventilation will cure any heat problems. As far as electricity goes, I run a 400watt MH 24 hrs a day, and a 400 watt HPS 12 hrs a day, with 7 total fans (exhaust, intake, etc) of which 2 are high powered. My electric bill is only about $40 more per month than it was previously which isnt much to have your own herb. The cost of the setup is where you will pay the most so dont worry much about the elec bill, unless of course you are trying to hide it from you parents which is a horrible idea seeing as they could go to jail if God forbid you got busted. If you live on your own and are just worried about the elec company catching dont worry you would need a huge setup for that to happen. Anyhow I hope I answered some of your questions...Peace Out and GG