does it have to be 100 amps? you could possibly run a 60 amp sub panel right off your current main panel, just takes a 60 amp 2 pole breaker and run the new wire to where it is going to terminate, the sub panel, you wire everything for your grow room, from there on either 15 or 20 amp breakers. And the wire probably won't be copper, most likely, aluminum, save you a few bucks. It isn't uber complicated to do but electricity seems to scare the shit outta most people. And unless you're planning on doing a huge grow, 60 amps should be more than enough to power 2 1000Watt hps, your fans, etc up to 60 amps total. You can power an entire house with a 100 amp panel. Total up the entire load you anticipate using on that circuit, you need a breaker just larger than that to power it safely. The 14/2 or the 12/2 wire you use for your circuits, will be copper, just to clarify, the feeder cable, aluminum. 14/2 = 15 amp circuits, 12/2 = 20 amp circuits. A 60 amp sub panel I think would take #4CU wire, basically just go to Lowe's or HD, and they will tell you what each size is rated for. Surf the net a little, and you can find detailed instructions about installing it all. Cost you well under a grand to do it yourself. And by using a sub panel, you won't have to have the power company come out either and no inspections. Personally, I think a 60 amp service would be plenty, add up ALL the amps that everything you plan on using, will use, max load, that tells you what your minimum size breaker/wire should be, go from there. Wire should be buried no less than 1 foot and I recommend running it in conduit, 2", maybe 1 1/2".
