Pool Heating
The first benefit of using a pool heater is an extended swimming season. Thanks to a pool heater, you can prolong the season by 3-5 months or even swim in the pool year-round (it will depend on the climate type in your area).
Solar Heating
Solar water heating is heating water by sunlight, using a solar thermal collector. A variety of configurations is available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications.
Natural Gas and Propane
The speed of heating the water depends on the heater type and environment conditions (air temperature, amount of sunlight).
If the main feature you are looking for in the pool heater is the quick heating of the water, a gas heater will be perfect for you. On average, it will increase the water temperature by 3-4ºF per hour which is 2 times faster than any heat pump (1-2ºF per hour).
The heat pump transfers the heat from the surrounding using electric current while the electric heater produces heat (like gas heaters do). What does this mean? That means that heat pumps are more efficient and will not cost a lot for operation, they are 6 times cheaper to run than electric heaters. But heat pumps need a constantly high air temperature to operate (over 50°F) and will heat the water 2 times slower than electric heaters.