Lumatek e-ballasts are the performance leader and the most reliable on the market. Use any 400w lamp, HPS or MH, with this ballast. It will produce up to 20% more lumens while saving you 5%-8% in electricity. Runs on a standard 120 volt outlet. Can run on 240 volts by just changing the power cord. The 240v power cord is sold separately. This e- ballast can run a 400 watt lamp at 400 watts, 275 watts or 250 watts. For best results use a 250 watt lamp when running at 250 watts. Now has the Super Lumens Switch giving you another 10% increase in lumens!( only with a 400 watt lamp). Now your light can "grow" with your garden by simply changing bulbs.