The efficiency of natural gas swimming pool heaters are measured by their output in Btu (British thermal unit) and is determined by a standard test. 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.
Find out why Gas Pool Heaters are the most effective for heating your swimming pool
The efficiency of a gas swimming pool heater is displayed on their nameplate. The manufacturer may also provide its efficiency percentage.It is not unusual to find gas pool heaters with 89%–95% efficiency. The Department of Energy has computed the savings one may obtain by installing a 95% efficient gas pool heater for every $1,000 in annual pool heating costs.
Table 1. 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 – source-Dept. of Energy.
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. Reading reviews of gas pool heaters are a good source of information.