hey Albert, wedfr, I don't have a normal space i need to cool. I'm on the top floor, so my ceiling is the roof with no insulation, I have a 25' long by 20' high wall of glass / skylight. In the summer the heat in that space would melt you. I solved the problem last year and installed a 35,000 btu wall unit. it kicks ass and will cool the entire 1,300 sq ft apt. I just can't run it 24/7, that would cost way too much. On days when the temp is nice and goes in the 80's my apt gets beaten on by the sun and heats up and extra 15 degree's. I won't always be around to turn the a/c on. So to keep the tank pegged at 80 I need at least a 1/3 chiller. I have 150 gallons total in the system. If I'm not home on the hottest day of the year I could actually have to pull the water down 30 degrees. I'd rather go bigger to be safe.