What to Consider when Choosing a Gas Pool Heater What to Consider when Choosing a Gas Pool Heater

Gas pool heaters are great for rapidly heating up or maintaining the temperature of a pool regardless of the outside temperature. However, with so many different types of heaters on the market, knowing which one is best for each individual application can become quite a chore. To make things easier consider the following:

Pool Usage

Gas pool heaters run on either natural gas or propane and work well in pools that need to be heated quickly. Unfortunately, because the cost of running these heaters is usually quite high, they are not recommended for pools that are used frequently throughout the year or pools that must constantly maintain a specific temperature. Instead, gas heaters are great for warming up a pool rapidly when guests drop by. Pools that are at summer homes or places that are only inhabited for short periods throughout the year are also good candidates for gas heaters. If a pool’s usage demands more constant or frequent temperature adjustment, consider either a solar or a heat pump style pool heater.

The Size of Heater Needed for Initial Heating

Heater sizes are described by the amount of British Thermal Units (BTUs) they can put out. A BTU is the amount of energy it takes to raise one pound of water, one degree Fahrenheit. The size of the heater needed for a swimming pool is determined by the size of the pool, the temperature the water needs to be raised, and the speed at which one needs to raise the temperature. To find how many degrees the temperature of the water needs to be raised, simply subtract the temperature of the outside air from the desired temperature of the water. Next, multiply the number of gallons of water the pool holds by 8.33 (the number of pounds in a gallon). Once this has been determined multiply the product by the number or degrees needed to raise the pool to the desired temperature. Finally, divide the product by 24 to learn the amount of BTUs per hour it will take to heat the pool. 

So, in the case of a 1,000 gallon pool that needs to be raised 10 degrees, the equation would be: first, 1,000 gallons multiplied by 8.33, which yields 8,330. The product 8,330 is multiplied by 10 degrees to yield 83,300. 83,300 is then divided by 24 hours which yields 3,470.84 BTUs per hour. Thus, to heat the 1,000 gallon pool 10 degrees, one would need a heater that put out at least 3,470 BTUs per hour.

The Size of Heater Needed for Maintaining Heat

The final consideration in determining what size of heater to get, is how much energy will be needed to maintain the temperature once it is heated. Usually, it will take about 10.5 BTUs per square foot of water, for every degree above the base line air temperature that the pool needs to be (this is assuming an average wind speed of 3.5 MPH). To calculate this, simply multiply the surface area of the pool by 10.5. Then, multiply that product by the number of degrees above the air temperature the water needs to be.

For example, if the 1,000 gallon pool from the example above had a surface area of 100 square feet, one would multiply 100 square feet by 10.5 BTUs to get 1,050 BTUs needed per degree. Then 1,050 would be multiplied by 10 degrees to give 10,500 BTU per hour of heat loss. Comparing that to the size of the heater needed for the initial heating of the pool, a heater that puts out 3,470 BTUs per hour would need to run about every 20 minutes or so in order to maintain a pool temperature that is 10 degrees above the air temperature in a pool with a surface area of 100 square feet. Depending on what the price of gas is in the area where heater is, one may want to buy a larger heater. A larger heater will raise the temperature more quickly which means it will run less, reducing the long term costs.

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