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Gas Swimming Pool Heaters

July 10, 2014 - 1:33pm


Gas Swimming Pool Heaters

Gas-fired pool heaters remain the most popular system for heating swimming pools. Today you can find new gas-fired heater models with much higher efficiencies than older models. Still, depending on your climate and pool use, they may not be the most energy-efficient option when compared to heat pump and solar pool heaters.

How They Work

Gas pool heaters use either natural gas or propane. As the pump circulates the pool's water, the water drawn from the pool passes through a filter and then to the heater. The gas burns in the heater's combustion chamber, generating heat that transfers to the water that's returned to the pool.

They're most efficient when heating pools for short periods of time, and they're ideal for quickly heating pools. Therefore, gas pool heaters can be a good choice for pools that aren't used on a regular basis. Unlike heat pump and solar pool heaters, gas pool heaters can maintain any desired temperature regardless of the weather or climate.

Selecting a Gas Pool Heater


  • Size
  • Efficiency
  • Costs.

Sizing a Gas Pool Heater



Gas pool heaters are rated by Btu (British thermal unit) output. Outputs range from 75,000 Btu to 450,000 Btu.


  1. Determine your desired swimming pool temperature.
  4. Calculate the pool surface area in square feet.

Pool Area x Temperature Rise x 12


Determining Efficiency of a Gas Pool Heater

New gas swimming pool heaters have a standard test they go through to determine their energy efficiency based on their Btu (British thermal unit) output.

Heater efficiency is the ratio of usable output to energy input. For example, an 80%-efficient heater uses $80 worth of useful heat for every $100 worth of fuel. Therefore, it wastes 20% of the fuel.

Most gas pool heaters feature their efficiency percentage on their nameplates. A pool heater's manufacturer can also provide its efficiency percentage.

Today, you'll find some gas pool heaters with 89%–95% efficiency. The following table shows how much you can save for every $1,000 in annual pool heating costs by installing a gas pool heater that's 95% efficient.

Table 1. Annual Savings by Gas Pool Heater Efficiency*
Current Htr Eff Cost w/ 95% Annual Savings
55% $580 $420
60% $630 $370
65% $685 $315
70% $735 $265
75% $790 $210
80% $840 $160

*For every $1,000 in annual pool heating costs

Estimating Gas Pool Heater Costs and Savings

The table below estimates annual costs of a using a gas pool heater for an outdoor swimming pool by location, by water temperature, and with or without using a pool cover.

Table 2. Costs of Outdoor Pool Gas Heating by Location*
Location Season Temperature
78° 80° 82°
Miami 1/1–12/31 $2136 $2848 $3600
w/cover 1/1–12/31 $416 $584 $800
Phoenix 3/1–10/31 $1384 $1776 $2216
w/ cover 3/1–10/31 $96 $168 $256
Dallas 4/1–10/31 $1512 $1920 $2456
w/ cover 4/1–10/31 $184 $280 $408
Atlanta 4/1–10/31 $1704 $2248 $2880
w/ cover 4/1–10/31 $320 $424 $592
Los Angeles 5/1–10/31 $1864 $2376 $2904
w/ cover 5/1–10/31 $168 $304 $472
Kansas City 5/1–10/31 $1434 $1872 $2384
w/ cover 5/1–10/31 $288 $416 $544
New York 5/1–9/30 $1448 $1904 $2384
w/ cover 5/1–9/30 $208 $296 $400
Chicago 5/1–9/30 $1621 $2072 $2536
w/ cover 5/1–9/30 $216 $296 $384
Denver 5/1–8/31 $1757 $2120 $2498
w/ cover 5/1–8/31 $123 $168 $243
Boston 5/1–8/31 $1712 $2096 $2504
w/ cover 5/1–8/31 $232 $328 $461
Minneapolis 6/1–9/30 $1331 $1776 $2176
w/ cover 6/1–9/30 $192 $248 $384
San Francisco 6/1–8/31 $1560 $1856 $2168
w/ cover 6/1–8/31 $192 $320 $472
Seattle 6/1–8/31 $1525 $1784 $2056
w/ cover 6/1–8/31 $304 $424 $552

*Figures based on a 1,000 square-foot, outdoor pool heated with an 80% efficient natural gas heater at $.80 per therm and uncovered for 8 hours per day.

If you're replacing a gas pool heater, you can use the following formula to determine your annual cost savings with a higher efficiency gas pool heater model:

Current Annual Cost x [1 – (Current Efficiency ÷ New Efficiency)]

Installation and Maintenance

Proper installation and maintenance of your gas pool heater can optimize its efficiency. It's best to have a qualified pool professional install the heater and even perform complicated maintenance or repair tasks.

Read your owner's manual for a maintenance schedule and/or recommendations. You'll probably need to tune up your pool heater annually. Also, scaling in the burner or heat exchanger may decrease efficiency over a period of time.

With proper installation and maintenance, gas pool heaters typically last five or more years.

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