Beautiful swimming pool
Swimming Pool Heater Guide

The Super Efficiency of Heat Pumps

~ Who else wants to extend their swim season? ~
In short, the heat pump takes heat from the air and puts it in your pool.

So lets list a few benefits:
highly efficient - around 500% on a warm day compared to resistance heating (such as a standard electric hot water system or kettle)
simple to install - can be done by a handyperson with electrical connection by an electrician
works on overcast days - heats the pool when you want it to
10 years plus lifespan with proper installation and maintenance
takes up little space
much cheaper to run than gas heater - around 50% to 70% cheaper
and, naturally, the downside:
as the air temperature drops, the heat pump becomes less efficient costing more to run
most don't work at all at temperatures below about 45°F (7ºC)
should be serviced annually by an air conditioning technician
up-front cost higher than gas and solar heaters
still uses electricity which has a nasty habit of rising in cost
Again, the use of a pool cover is highly recommended to cut down on heat lost due to evaporation. It's a lot easier to lose heat from a swimming pool than it is to put it in so once you have it, do your best to keep it.

The following table will provide a guide to what you can expect a heat pump's running cost would be depending on your location - figures are included for with and without a pool cover, take note of the difference. Please remember, these figures are an estimation and your situation and use may differ.

More up-to-date figures may be available on the EERE website.
Location Season   Required Pool Temp
78⁰F 80⁰F 82⁰F
Miami (no cover) 1/1 - 12/31 $1,100 $1,460 $1,845
with cover $215 $300 $410
Phoenix (no cover) 3/1 - 10/31 $680 $875 $1,090
with cover $45 $85 $125
Dallas (no cover) 4/1-10/31 $760 $970 $1,240
with cover $90 $140 $205
Atlanta (no cover) 4/1-10/31 $840 $1,110 $1,425
with cover $155 $205 $290
Los Angeles (no cover) 5/1-10/31 $950 $1,210 $1,485
with cover $85 $155 $240
Kansas City (no cover) 5/1-10/31 $715 $935 $1,185
with cover $145 $205 $270
New York (no cover) 5/1-9/30 $740 $975 $1,220
with cover $105 $150 $200
Chicago (no cover) 5/1-9/30 $810 $1,035 $1,270
with cover $105 $150 $195
Denver (no cover) 5/1-8/31 $875 $1,055 $1,245
with cover $70 $100 $150
Boston (no cover) 5/1-8/31 $875 $1,075 $1,280
with cover $120 $165 $235
Minneapolis (no cover) 6/1-9/30 $660 $850 $1,040
with cover $100 $125 $190
San Francisco (no cover) 6/1-8/31 $800 $950 $1,110
with cover $95 $165 $240
Seattle (no cover) 6/1-8/31 $770 $900 $1,035
with cover $150 $215 $280

Costs by Location of Heating Outdoor Pools with a Heat Pump*

*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 courtesy of US Dept of Energy's Energy Efficiency and Renewable Energy website -
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For energy efficiency it is very hard to go past a heat pump. Heat pumps are becoming more widespread for water heating due to their low operating cost.

What is a heat pump? You probably have at least one in your home already - refrigerator, freezer and air conditioner (not the evaporative type) are all heat pumps. They use a compressor, refrigerant gas and a heat exchanger to move heat from one place to another.

Basically, a liquified refrigerant gas is pumped through a heat-absorbing coil (called an evaporator) which is positioned in warm air. The liquid absorbs some of the heat and turns back into a gas. The warmed gas is then compressed, turning it into very hot gas.

The hot gas then passes through another heat exchanging coil immersed in water (pool water in a pool heater) which absorbs the heat from the gas which turns back into a liquid and passes back into the heat-absorbing coil and so on.
Diagram Courtesy of GMC Thermal Solutions