Re: grow lights ?
if i were to take a wild stab at this question i would have to say no..
because there is 1000w of energy being used in something that only needs 400, SO you would end up with a bulb shattering when you turn it on.
Im not 100 percent sure but from a little knowledge of electronics it would make sense to me.
NOW
you could possibly use a 1000w bulb in a 400w ballast although i dont know why you would want to do that because A) it would be a waste of money and B) you would not get the same amount of power wich would mean that the light would not be as bright.