Solar is definately less expensive in the long run if you have the solar exposure (I assume you do in Arizona) and you don't mind the looks of the panels. My pool is tucked in among the trees and we get less than an hour of full direct sun per day on our pool. Used solar for five years, but the wife was always complaining about the panel (didn't want it on the roof or patio, and it would kill the grass). So I got rid of her -- the solar panel, not the wife! Installed an electric heat pump last week. Pool temp jumped 12 degrees the first 24 hours! It works like an air conditioner, only backwards. Blows cool air out and puts warm water into my pool. That guy in DC may be on to something. I've been thinking the past couple of days it would be nice if I could harness that cool air and get it into my house. Guess it's too late to convince the wife that the ducting would look good ;-)

Good luck