A light system will increase your electricity cost -- the exact amount depends on the size of the system and the number of hours operated. However, since these grow lights are so energy efficient, you are getting huge amounts of light (and growing power) for your money! Make sure your grow room's power circuit can handle the power draw. For safety reason, do not exceed 75% of the rated ability of the fuse/breaker (for example: use no more than 15 amps on a 20-amp circuit).