Heat of Metal Halides

I have another question with regard to metal halide lighting.  As I have dug deeper researching MH systems there seems to be one common comment from everyone I talk to.   This comment is that these lights throw an enormous amount of heat.  I would like to ask anyone in the group using MH how you would rate the heat generated, how this heat affects your tank and if you take any special steps to counter this probem, if it is indeed a problem.
I think that in my personal situation, the excess heat will be welcome in the winter (as I live in WI), however in the summer it will be a major factor as I don't have AC in my home.  To Refresh your memory, I have a 150 gallon tank (6' x 2' x 18"wide).

Scott Corbeil