hps wattage needed for 2 plants?

umm do all hps systems need to use the ballast? if so why? to move heat? umm whats the minimum watts to get in hps to grow 1-2 plants?

would 150hps do?

is it comfortable to put hps in the same room your going to sleep in? if not are there other lights comfortable to put in the same room you sleep in?

they have 50-75 watt hps lights that you can use for growing.a 150 would do good and heat would be minimal.As long as you have something to seperate your grow from your bedroom you should be fine.I use a 400 watt behind my bedroom.

150w will do for 2 plants

the reason you use a ballast is to regulate the flow of electricity
http://en.wikipedia.org/wiki/Electrical_ballast

also yes 150 watts will be good but even at 1gram per watt thats not a shit ton of weed unless you just want some personals for like a month or two. i would recommend getting a 400 watt

also before posting next time there are already quite a few threads that answer both your questions so please use the search feature before asking questions that seem like they might be commonly asked. thank you.