What I think nubby is trying to say is, 'HID lamps, as well as other growing equipment, pull a lot of 'power'.... The 'power' used in a grow room can potentially become a lethal amount, before you start plugging in High wattage ballasts and such things you should do a bit of research on 'amps, amperage per circuit, amount of amps drawn from your equipment etc. Once you understand the basics, you then can pull out your calculator and you will know exactly what to plug in so you don't, by accident burn you or your neighbors house down.
Love GG