Conversion bulb questions

Hey i was wondering about conversion bulbs, i read that they produce less light, and some companies even advertise that the use less watts. They make it sound like it uses less watts from the outlet, but i would assume they mean that the ballast uses 400w while the bulb only uses 360w of those watts. Am i wrong, do conversion bulbs actually use less watts from the power company? Also if they do use less watts im assuming they would also run cooler. Anyone have any info on this, particularly MH to HPS bulbs. Any help would be greatly appreciated. Thanks. Lampshade.

im gona guess about the electricity use and say that the ballast will always use the same electricity.

from personal experience, i notice that the temp goes down switching to hps. that metal halide conversion bulb(600 watt) seems to keep the area 5 or more degrees warmer. being its a cool deluxe and all, that shit is hot.

Cool thanks. Anyone second that?

Also your saying it was hotter with the conversion bulb, in your case the MH?