I have an evacuated tube system with six panels that helps to heat my 100,000L (25,000 US gallon) pool but I am in Toronto so I need it much more than you would in FL. The system works well - the initial cost was about $4000 and the payback is about four years. This is my third season so it has almost paid back. My understanding is that evacuated tube is better in providing heat when the ambient temperature is much lower than the desired pool temperature so it wouldn't be suitable for a place like FL, except for the winter. The only downside is that the system causes air bubbles to be coming out of my return jets due to pressure imbalances caused by the water flowing up to my roof and then rushing back down to the pool which is about two floors below the roof at this part of my house.