You'll need more than just a CFL to grow one plant but if you get the 400w HPS be sure to grow more than one plant, rumor has it that it is possible to put 12 - 16 plants under 400w HPS, although you'll need more than just a box.You can actually lower your electric bill by changing your house bulbs to 26 watt cfls and then buy a 400 watt hps and grow a real plant for less money..