all light fixtures are rated diffrently the most common ones are 40w 60w 100w 150w in the medium base like an "a-type" light bulb but ive seen em as high as 4000watts @ 10000 volts for mogal (the giant hid base) ya just gotta make sure you base is rated for the wattage/voltage your using ...

on another note im a big fan of 48" 8 bulb bathroom vanity fixtures there like 15-25 bucks depending on quality and finish there rated for 60w bulbs so they have no problem takin the 42watt cfls so thats like 300watts for 30-50 bucks after bulbs and wire