You might want to have a look at my "Dealing with heat issues" thread. (in my signature)
I flower in an outdoor shed, and I live in the desert where outdoor temps exceed 100 degrees daily.

I'd go bigger if you can afford it. Larger units are usually a tad more efficient during the heat of summer, and it's best not to have a smaller A/C on full-blast all the time. (electricity and wear-n-tear)
Rusty Trichome Reviewed by Rusty Trichome on . Air Conditioning Unit Help Hi. Does this work: 10,000 BTU portable a/c unit, cooling a 1000W HPS in a 4' x 6' x 8' room (192 cubic feet), exhausting air 20' UP through the attic and out the roof. The unit's exhaust is roughly 250 CFM. If this doesn't work, could someone give me suggestions on how to make it work? For example, what size a/c unit would work? Or, could I 'assist' the unit by installing an inline fan half way up the ducting, at around 10'? The problem with this latter solution is I don't know how to Rating: 5