Quote Originally Posted by Zandor
I do not agree with you here.

Most of the power consumed is by the transformer not the bulb. The gas inside the bulb get's hot to produce the light but no where close to the 75% you are saying. Heat is a by product of the gas producing the lumens. (light)

Most of the energy is spent transforming the power from 120v input to the 240-277v AC output the light requires to burn. That is where most of the true heat and the power come from.

There is nothing wrong with cooling the bulbs in an air-cooled hood. I have used them for many many years with great success. The amount of light the bulb produces is not affected once if the bulb is cool or not. The glass does take away a few lumens but nothing you or your plants would notice. The savings in heat is well worth the very little light given up by the glass.

I have measured it many times with my light power meter and have found less then 1% decrees in the lumens with cool tubes or air-cooled hoods.

A cool room is way better then a hot room any day!!!!!!

I have to disagree with you and side with Karma.
Simple facts are your bulb needs to be a certain temp in order to fire the lumens we expect of it cooling it only increases the time it takes to actually produce what its suppose to.
As far as someone saying its this % or that % whos to say for sure we all have different setups and I am sure results do vary but on the standard idea behind the bulbs we use cooling them does effect the output.
DFG