If you are going to run the A/C, that's a great idea. I collect rainwater in a barrel from my downspout and never turn the A/C on. My utility company just had to pay me back from even billing excess (yay

). We have a whole house attic fan that we run all night in hot weather. Sucks the heat out from the top of the house and pulls cool night air in. Works great as long as there is cool night air. When we get to the dog days in august when it never cools off, we just sleep in the basement. Stays tolerably cool.