Metal halide ballast questions

My father in law has two metal halide fixtures with two 400w ballasts. I was wondering if I had to use 400w bulbs or if I coul use smaller bulbs. My wife dosent like the idea of 800w of electricity.

 

Under most circumstances, no! You must use 400w bulbs unless they are switchable ballasts that allow other wattage bulbs to be run.

 

Many people,myself included,find that LED fixtures will pay for themselves in a sometimes relatively short time with lower energy cost and no cost for replacement bulbs.