have you given taughts to liquid to liquid geothermal units withproper coil material for your pool water.Typicaly the offer from 300% to 400% efficiency over electricity (bassicaly take a planned electrical cost and divid by 3 to 4). You would have to find a undeground source of water of addequate gal/min and pipe it to the geothermal unit (with the option to pipe it to a solar heater before). Initial cost can be pretty steep but return on investment can be anywhere from 5 to 15 years depending on applications