Ballast: 120 v and 240 v

Im adding a 400w hps into my setup but how do i know if i need the 120 v or 240 v ballast. also, should i opt for an electronic ballast like the future brite or one like the sun leaves luma 2.0?

You can get ones that you don't have to make those decisions with. It will run off 240 or 120 by flipping a switch. The electronic ballast is better slightly more energy efficient and quieter. I don't recommend either of those. Instead of a 400 hps you would be better offf with a t-5 if you can afford it. $340.00 out the door including the necessary air cooling because it doesn't need any. VV