250 watt HQI ballast.

[Delphinus]

I don't think we're flogging a dead horse. I think it's been interesting so far.

First of all I'm not sure that I am in disagreement at all about:

my personal experience dictates running a seperate line to something which is going to draw more current than normal.. so this is why i push it..

That's exactly what I was thinking, too. I would try to minimize overloading any one circuit by spreading the load onto different circuits. Personally, if I was anywhere near a 15amp load on a single circuit, I'd be very nervous about that. I'm much rather, for example, see 12amps split between two circuits, instead of all on one circuit.

It seems me that you're saying that one can take this one step further, instead of putting "this and that on circuit #1" and "this other thing and that other thing on circuit #2", we're now putting "half of this one item on circuit #1" and "the other half of this one item on circuit #2." If my device had a serious amperage draw by itself then I understand why you would want to do this. But the typical amp draw for metal halides is going to be in the 2-4 amp ballpark, which to me, seems not entirely unreasonable to have one or two of these on a circuit and then be done with it.

the benefit is safety and convenience.

Is 220V inherently safer than 110V? If we're going to introduce variables such as "shoddy wiring" then it seems to me that 220V is potentially "twice as dangerous" as 110V. Convenience be one thing, efficiency be other thing, and safety be yet another thing.

the arguments should not be "The lights aren't going to burn any brighter, the ballasts aren't going to run any less hot, the watts consumed aren't going to be any less"

I think they are still valid questions though. Even if the answer is "it won't make a difference" they should still be asked. If it's better to do "function 'X'" in one method over another, why not pursue that?

My thinking was that as far as the "overall efficiency" (which I, personally, measure in terms of "what did the utility company charge me this month"), 220V vs. 110V won't make any significant difference. Nothing in the ensuing discussion since the question was originally asked, has suggested otherwise. The only good reasons have been about load balancing and minimizing overload. If one's circuits are not closely approaching their limits then I don't see a burning need to rip apart my house and install a 220V circuit. If they were, however, taxed close to their limits, or perhaps I was building a new tank room that I wanted to service who-know-what-kind-of-future-needs, then yes, I see the "benefit."