The following information and recommendations are based on over 25 years of experience in pool installation and maintenance in Western PA

Electric pool heaters (Heat Pumps) cost more than gas pool heaters, but they are generally more efficient and cheaper to operate. With proper maintenance, electric heat pumps typically last longer than gas pool heaters. Electric heat pumps are essentially an air conditioner in reverse. They are also larger in size and heat much slower than a gas heater. Electric heat pumps work efficiently as long as the outside temperature remains above the 45ºF–50ºF range. Recommendations are situation dependent based on service availability and a number of other factors. For certain customers, heat pumps are a great option to consider.
Pros: Lower operating costs, environmentally friendly, lasts longer
Cons: Requires warmer ambient temperatures, higher initial cost

Natural gas heaters are able to maintain a constant water temperature in any weather conditions and heat water much faster. We do not recommend propane. If you want to keep your pool warm when it is colder (below 55ºF), then gas is your best option. If you OVER-size a gas heater you can get your pool to temperature quickly and with decent efficiency. Again, dependent on a number of factors, we often recommend gas heaters to customers if an adequate gas supply line is available.
Pros: Heats pool quickly, lower initial cost
Cons: Higher operating costs, generally fails sooner