Gas pool heaters
With a gas pool heater you’ll need to decide between running it on natural gas or liquid propane. For that reason, you’ll want to pay attention to the availability and the price of gas in your area. Also, if you select propane, remember you will have to refill and hook up the propane tank on a regular basis.
Because of the speed at which a gas pool heater can heat pool water, they make a good choice if your above ground pool is used less frequently, say on weekends or only a couple times a week. In these cases, you’ll only need to run a gas heater when you use the pool. If you fire up a gas pool heater in the morning you can be enjoying a warm pool later that afternoon. And while it may actually cost you more to run the gas heater, your overall cost won’t be that significant because you’ll be running the gas heater less frequently.
Also, as mentioned earlier, gas pool heaters represent a better option if you live in a colder climate. Typically, a pool heat pump will not heat a swimming pool nearly as well as a natural gas heater during the colder months.
If you missed it here is part 1 of A General Guide to Pool Heating options