I have a 25K Gal In ground Pool in South East Pa. I currently have propane for my furnace, Hot Water Heater, Stove/Burners, and 13Kw Backup Gen. I have a 500 gal underground tank, and could get the gas to my pad where the pool heater would go. I talked to the guy at the pool store and he said the bigger the better, but is there a point where the size of the heater becomes less efficient? I would like it to heat as quickly as I can. What size should I get