I have this same problem, as im doing it in my house. So how to do it without attracting too much attention from the parents? First i start off with 2 compact floresents. Im not too sure how much they raise the light bill, but im pretty sure its not a terrible amount, maybe like 5ish a month. The other way to reduce electricty costs are buy a timer and use electricity at night. 18/6 cycle at night is much cheaper than using electricty during the day. When you want to flower, im using a 250 watt HPS (I think my parents are getting suspicous cause these burn that electricty) I keep it on night cycle cause night electricty is about 10-20 times cheaper. Thats a bare minium grow set-up if you want a semi-decent harvest..Im hoping for around an ounce to an ounce and a half per plant...I might he hoping too much