We just bought a new house in Orlando that has a pretty good size pool, I would say at least 15k gallons if not more with attached spa (pool is 15x30x6). The current owners had a large propane tank sunk for other reasons so they went with a gas heater.
In any case, I am trying to decide what kind of pool heater to get for the new house. I have a pool at my current house (in Orlando) with a 120k btu heat pump and it's nice and efficient, but it's noisy and takes a long time to heat unless it's above 75 degrees outside. I use the pool a lot (I work from home) and I like the temperature to be between 85-88 degrees when I swim.
I've read some of the pros and cons of the two types of heater, but have not zeroed in on a real consensus for my type of situation. The gas heater would be cheaper to install initially, especially because there is already a tank nearby, but I have no idea how much it's going to cost me in the long run. Propane here is currently around $5/gallon. Electric is $0.12/kW.
In summary: I use the pool frequently, but only for short periods at a time. I like it "hot" (i.e. 85 or above) but I don't want a lot of noise or long term expense. It's a northern exposure, and a fairly large pool with attached spa. There is already a sunken gas tank near the pool area. Which heater would be most economical for my situation? We plan to be at this new location long term, like 15 years.