You do not have to be on the natural gas grid to use propane as it can be stored in large storage tanks right on your property. Like natural gas, liquid propane provides fast heat. Liquid propane has the same disadvantages as natural gas, and it is significantly more expensive than natural gas.
Fuel oil is readily available and can be delivered to storage tanks on the pool owner's property.
Its cost varies depending on geographical area, but generally can equal or exceed that of liquid propane. Like other fossil fuels, fuel oil provides fast heat. Fuel oil heaters are not odorless, so it's best to place the fuel oil- fired pool heater away from the pool and recreational area. Electricity is universally available. Electric pool heaters are flameless and small.