I set up a pretty nice outdoor stealth growbox a while ago. I had a trash bin, with about a 2x2 base and about 4.5 feet tall. I found a portable camping heater in there that kept the appropriate temperature. Then I ran a extension cord out to the bin (you kind of have to bury it), for four 20 watt cfls. Then I drilled some holes in near the bottom, and covered it with cuttings from panty hoes for air circulation. It worked pretty good, too.