Magnetic or digital ballasts are an essential for any indoor grow room as High Intensity Discharge (HID) grow lamps such as HPS and MH cannot run without one. The purpose of the ballast is to limit and regulate the power for stable and safe operation. Ballasts MUST match the rating of the grow lamp. For example, a 600w lamp MUST be powered by a ballast with a 600w rating. Under no circumstances should a 400w, 600w or 1000w grow lamp be run from a 250w ballast.