Pool Heater Questions

Frequently asked questions about pool heaters

Pool heater questions

Here are some common pool heater questions. Scroll down for the answers.

* How much does heating a pool cost?
* What size of heater do you need?
* What sort of heater should you use -- a traditional gas pool heater or a heat pump pool heater?
* What else should you know about buying a pool heater?
* After buying a heater, what can you to save money on heating?


Cost of pool heating (A pool cover saves a lot of money)

The chart below shows the average cost of heating a pool in South Florida for the year. The figure is based on a 1000 square foot outdoor pool heated with an 80% efficient natural gas heater at $.50 per therm. The dramatic cost difference for using a cover is also shown. It`s assumed the pool is uncovered for 8 hours per day.



Miami: 1/1 thru 12/31 (78 degrees) $1335, (80 degrees)$1780, (82 degrees) $2250


Costs WITH a pool cover: 1/1 thru 12/31 (78 degrees)- $260, (80 degrees)- $365, (82 degrees)- $500

Pool heater size

Pool heaters are mainly sized according to the surface area of the pool and the difference between the water and average air temperatures. One method uses the following procedure:

1. Determine the desired swimming temperature.

2. Determine the average temperature for the coldest month of use.

3. Subtract the average temperature from the desired temperature to get the temperature rise needed.

4. Calculate the pool surface area.

5. Use the following formula to determine the Btu/Hr output requirement of the heater.
PoolArea x TemperatureRise x 12

This formula is based on 1° to 1-1/4° F temperature rise per hour and a 3-1/2 mph average wind at the pool surface. For a 1-1/2° F rise multiply by 1.5. For a 2°F rise multiply by 2.0.

The heating load is also affected by other factors such as wind exposure, humidity levels and cool night temperatures. Pools located in areas with higher average wind speeds at the pool surface, lower humidity, and cool nights will require a larger heater.

This calculation will give you an approximate size. You should have a trained professional perform a proper sizing analysis for your specific pool.


Gas pool heaters

Today the most popular method of heating pools is the gas-fired pool heater. Heaters are built for either natural gas or propane.

Gas appliances have become increasingly more efficient in recent years. With innovations in hydraulics, heat exchanger technology, forced draft combustion systems, and pilot-less ignitions, efficiency has almost doubled in recent years. High efficiency pool heaters are now available that are 89-95% efficient.

Heater efficiency is the ratio of usable output to energy input. For example, with a 80% efficient heating appliance, there is $80 worth of useful heat for every $100 of fuel bought. 20% of the fuel is wasted.


Heat pump pool heaters

An emerging method of heating pools is the heat pump pool heater. A heat pump`s efficiency is dependent on the outside temperature and since pools are usually used during warm and mild weather, heat pumps are a very efficient method of heating pools.

Heat pumps do not generate heat, they simply capture it and move it from one place to another. Below is a diagram that shows how heat pumps operate.

heat pump pool heater

How efficient is a heat pump? That`s not an easy question to answer. Heat pumps don`t have a simple efficiency number to work with. Their efficiency is measured by Coefficient of Performance (COP).

Just like other heating options, heat pumps can have low efficiencies or high efficiencies. Their COP can range from 3.0-7.0. The higher the number the more efficient the heat pump. What this means is that for every unit of electricity that you put in to run the compressor, you get 3-7 units of heat out of the heat pump. These COPs are usually determined by testing the unit with an outdoor air temperature of 80°F and a water temperature of 80°F. But there is no standard test, so you should be aware of this. The higher efficiency units usually use scroll compressors versus the reciprocal compressors of the standard units.


Buying a pool heater

Efficiency is one consideration in buying a pool heater, but you should also consider the reputation of the manufacturer and/or dealer who will install your heater. Get some references of satisfied customers and call the Better Business Bureau if you don`t have anything to go on. Also be sure to ask for and read all warranties before making your decision.


Pool heater money saving tips

Regardless of what pool heater you buy, here are some tips to help you reduce your heating costs.

* Keep a thermometer in the water. It will help you determine the temperature that is perfect for you. (For more about pool temperature, click here.)

* Keep your thermostat at the lowest setting that still maintains a comfortable swimming environment.

* Mark the "comfort setting" on the thermostat dial to avoid accidental or careless overheating.

* Lower your thermostat setting to 70° when the pool is to be unused for three or four days. For longer periods, shut the pool heater off.

* Protect your pool from wind. Use a fence or hedge. A 7 mph wind at the water surface can triple a pool`s heat loss.

* Use a pool cover when the pool is not in use. This can reduce your the energy consumption by 50-75%.

* Get your pool heater tuned up annually. A properly tuned pool heater will operate more efficiently.

Click here for more swimming pool money saving tips.

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The pool heater information above was edited by Chris Whitten based on source material from the U.S. Department of Energy RSPEC (Reduce Swimming Pool Energy Costs) Program, which is now defunct.