These data are simply calculated values, so you will need to make considerations with your eventual pool heater selection, since they are commonly sized in 50,000 BTU/Hr increments. Also, this data is based on the heating units operating at an 80% efficiency. Gas pool heaters are available that exceed this rating, so an appropriately smaller sized unit could be substituted.

Gas pool heaters are rated based on the BTU input of the heater. Natural gas has a heating value of 1,000 BTU/cubic foot, so a 100,000 BTU/Hr heater that operates at 80% efficiency would transfer 80,000 BTU/Hr of heat to the pool water. A heater with an efficiency of 90% would transfer 90,000 BTU/Hr to the water and result in a fuel savings of approximately 13%. This will have a greater impact on your fuel budget the more that you use the heater, so the greater expenditure for a higher efficiency system may justify the higher capital cost.

A pool heater that can raise the water temperature by 30 degrees is needed if you plan to use your pool in early April through October (and you live in the NE US) when the air temperature is 50 deg, but if you only want to extend your swimming season by a month on each end then a smaller sized unit would suffice. A smaller unit would also work out well for you if you can run it for several hours to warm the water or only need to supply the water temperature of the daytime with some additional heat at night or on overcast days.

Again, these tables are presented as a guide. Discuss your specific requirements with your pool equipment supplier. However, for most homeowners with above ground swimming pools, a heater that is rated at 100,000-200,000 BTU/Hr will handle many situations. But if you are to err on one side or the other, you will never be disappointed by choosing a larger unit over a smaller one.

Table 1: 1 deg F Rise/Hr

	10 deg F rise	20 deg F rise	30 deg F rise
Round Pools
15	26494	52988	79481
18	38151	76302	114453
21	51928	103856	155783
24	67824	135648	203472
27	85840	171680	257519
30	105975	211950	317925
Oval Pools
15 x 30	60244	120488	180731
18 x 33	78651	157302	235953
18 x 40	97551	195102	292653

Table 2: 2 deg F Rise/Hr

	10 deg F rise	20 deg F rise	30 deg F rise
Round Pools
15	52988	105975	158963
18	76302	152604	228906
21	103856	207711	311567
24	135648	271296	406944
27	171680	343359	515039
30	211950	423900	635850
Oval Pools
15 x 30	120488	240975	361463
18 x 33	157302	314604	471906
18 x 40	195102	390204	585306

There are three main pool heater technologies that are in common use today: the gas pool heater, the electric heat pump and the solar pool heater. Electric pool heaters that you used a resistance heating element and fuel oil fired pool heaters were also fairly common in the past, but due to the high operating cost associated with their energy sources they have fallen out of favor with the public.

Gas powered pool heaters utilize either natural gas or liquid propane as a fuel source. They are relatively simple pieces of mechanical equipment and consequently have the lowest capital cost associated with them. However, although natural gas and liquid propane prices have stabilized recently, gas pool heaters still have the highest operating costs relative to the other technologies. But at the same time, newer gas heaters can operate at 80% or greater efficiency and that leads to an offset of the energy cost. Another benefit of gas heaters is their ability to raise the water temperature in a short period of time.

Electric heat pumps are finding more use today since there have been advances in the efficiencies and technologies associated with them. They are very similar to the heat pumps used in home heating systems and work in much the same way as a central air-conditioning unit does, only in reverse. The systems use a chlorofluorocarbon like Freon and utilize the thermodynamic properties of the expansion and compression cycles of gasses and fluids. The low pressure side of the system is a gas and this gaseous fluid is forced through a nozzle into the high pressure side of the system where heat is released. This heat of compression is used to heat the pool water. Although electrical energy is not used to heat the water directly, electricity is required to operate the pump that moves the fluid through the system.

Solar pool heaters collect the radiant heat of the sun through their solar panels. This radiant energy is transferred to the water through the high surface area of the panels. This is analogous to the solar energy of the sun hitting the pavement or the beach sand. The pool water is circulated through the solar panels by a pump that is operated by a control panel. The pool thermometer sends a signal to the control panel that instructs the pump to keep circulating water to the solar panels until the water temperature reaches its designated setting.

Obviously, solar panels have the lowest energy cost associated with the operations. However, this is somewhat offset by their high initial cost due to their plumbing and installation. Additionally, solar panels also require a significant area for installation and access to the sun's rays so there may be siting constraints involved. Therefore, the use of solar panels is somewhat restricted by the available area to place the panels and a geographical area that is subject to strong sunshine.

The choice of the correct pool water heating system for your specific application depends on several factors, which should be discussed with your pool equipment supplier. The major factors that need consideration are:

• The water temperature desired
• The rate or time that you prefer to raise the pool water temperature
• The months that you need to heat your pool
• Your climatic location
• Availability of direct sunshine on the pool
• The availability of a fuel source
• Your budget for capital costs (equipment and installation)
• Your operating budget (electricity and fuel costs)
• The expected life of the pool heater

I was thinking about selling it and wondering if we could get anything for it?

My gas pool heater stopped working. I have reset the circuit breaker and there is electrical power at the heater itself. I have also visually inspected the wiring and do not see any problem areas.

What else should I look at? Thanks!

I have found a used 250,000 BTU Hayward pool heater that I'd like to use to heat our pool. It's a natural gas fired unit, but I'd like to use propane instead. I understand that you can convert natural gas pool heaters to propane, but I don't know what is involved. Do I need an additional part? Any help is appreciated.