Managing Swimming Pool Water Temperature for Energy Efficiency

The water temperature you desire for your swimming pool not only affects the size of the pool's heater, but also your heating costs if use a gas or heat pump pool heater.

Pool water temperatures typically range from 78ºF to 82ºF. The American Red Cross recommends a temperature of 78ºF for competitive swimming. This coincides with good fuel savings. However, this may be too cool for young children and the elderly, who may require a temperature of 80ºF or higher.

The energy consumption for each degree rise in temperature will cost 10%–30% more in energy costs, depending on your location. In warmer climates, this percentage is higher because of the relatively low cost of heating a pool at 78ºF. The tables below show the costs of heating pools at different temperatures in different U.S. cities.

Estimating Heat Pump Swimming Pool Heater Costs and Savings

For an outdoor swimming pool, use the following tables to help estimate your annual heat pump pool heater costs and savings compared to using an electric resistance or a gas pool heater.

Table 1 estimates annual swimming heat pump pool heating costs by location, by water temperature, and with or without using a pool cover.

Table 1. Costs by Location of Heating Outdoor Pools with a Heat Pump*
Location Season Temperature
78° 80° 82°
Miami 1/1–12/31 $1100 $1460 $1845
w/ cover 1/1–12/31 $215 $300 $410
Phoenix 3/1–10/31 $680 $875 $1090
w/ cover 3/1–10/31 $45 $85 $125
Dallas 4/1–10/31 $760 $970 $1240
w/ cover 4/1–10/31 $90 $140 $205
Atlanta 4/1–10/31 $840 $1110 $1425
w/ cover 4/1–10/31 $155 $205 $290
Los Angeles 5/1–10/31 $950 $1210 $1485
w/ cover 5/1–10/31 $85 $155 $240
Kansas City 5/1–10/31 $715 $935 $1185
w/ cover 5/1–10/31 $145 $205 $270
New York 5/1–9/30 $740 $975 $1220
w/ cover 5/1–9/30 $105 $150 $200
Chicago 5/1–9/30 $810 $1035 $1270
w/ cover 5/1–9/30 $105 $150 $195
Denver 5/1–8/31 $875 $1055 $1245
w/ cover 5/1–8/31 $70 $100 $150
Boston 5/1–8/31 $875 $1075 $1280
w/ cover 5/1–8/31 $120 $165 $235
Minneapolis 6/1–9/30 $660 $850 $1040
w/ cover 6/1–9/30 $100 $125 $190
San Fran 6/1–8/31 $800 $950 $1110
w/ cover 6/1–8/31 $95 $165 $240
Seattle 6/1–8/31 $770 $900 $1035
w/ cover 6/1–8/31 $150 $215 $280

*Figures based on a 1,000 square foot, outdoor pool heated with an air to water heat pump with an average COP of 5.0 at $.085/kwh.

Table 2 estimates the annual savings of using a heat pump pool heater compared to using an electric resistance or gas pool heater.

Table 2. Annual Savings Comparisons of
Gas and Electric Pool Heaters*
Efficiency Annual Cost Cost w/ 5.0 COP Heat Pump Savings
Gas Pool Heater
55% $584 $200 $384
60% 535 $200 $335
65% 494 $200 $294
70% $459 $200 $259
75% $428 $200 $228
80% $402 $200 $202
85% $378 $200 $178
90% $357 $200 $157
95% $338 $200 $138
Electric Resistance
100% $1000 $200 $800

Based on an electric resistance heated pool, which costs $1,000 per year at an electric cost of $.085/kwh, and using a natural gas cost 0f $.80/therm. A seasonal average COP of 5.0 was used to determine heat pump savings.

Estimating Swimming Pool Gas Heating Costs and Savings

Here you'll find information to help estimate annual gas heating costs for an outdoor swimming pool and/or savings if you replace a gas pool heater with one that's more energy efficient.

The table below estimates annual costs by location, by water temperature, and with or without using a pool cover.

Table 3. 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 $.50 per therm.

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:

The formula is current annual cost multiplied by one minus current efficiency divided by new efficiency.

Also, turn the temperature down or turn off the heater whenever the pool won't be used for several days. This will save energy and money. It's a myth that it takes more energy to heat a pool back up to a desired temperature than you save by lowering the temperature or turning off the heater.

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