MH use quite a bit more energy then HPS (except during ignition). As long as your grounded and you know which breaker it is, keep an extra one on hand. Thats what breakers are for. That said, what I try to do is distribute the energy around. Instead of everything hooked up in one room, get it hooked up on a few different circuits.

A good surge protector (this way you have 2 failsafes), basic knowledge of how circuits work, and an extra breaker or two and he should be fine.

Last, the only time I ever popped a switch is when I started up 3000 watts all at once and didnt realize that the A/C somehow got switched to the same circuit. We then made it so each light turned on 1 minute after the other. HPS draw the most amperage when they ignite, however for a 1000 watt Id say it barely hits 15 amps (which is still quite a bit) and only for a few seconds.

Now obviously, all this doesnt matter if you have some super old shabby spot with nasty wiring thats beginning to be overloaded.