My neighbor works for a company that sells swam coolers that do not add moisture to your house. It cools the air the same way as a swamp, but the moisture is contained and drips out of the unit itself into the yard. He's been telling me that if an A/C unit of the same size as his unit takes 4,500 watts to run, his takes 450 watts. The company is called Coolerado.

http://www.coolerado.com/how-coolerado-works/