Dont buy a chiller ... use a heat exchenger

[PoonTang]

I'm surprised that nobody mentioned using ground source cooling. Think of a ground source heat pump in reverse. Would cost you zero to run and is the greenest of all options. Simply t-off of your return pump and run it out to cooling coils buried out in your lawn and then back into your sump. There is actually a chapter in j Sprung's books on how to do it.