[ELGo]

Here is my last attempt to explain why I think you will waste energy and money:

1. Cheap energy to cool the water -- good
2. (Albeit Cheap) energy to cool the *entire* thermal mass of the house to temperatures below what you would otherwise would, causing an increased gain of heat until the house equilibrates with the outside ambient -- not good.

Your approach requires (2.) to achieve (1.)

This will make more sense if you are familiar with Newton's law of heat transfer.