How to Choose a Pool Heater: Gas Heater, Heat Pump or Solar Heater?

Last Updated: | By Barack James


During cold seasons like winters, swimming pools are always ice cold and most of them go under winterization, which means they are closed for the whole periods of the winter and fall.

However, Winterization is not always an option for most of us who like swimming and warm baths. You can enjoy your winters and any cold weather days in a spa without worrying about ice cold water, thanks to pool heaters. 

There are 3 main types of spa heaters; gas heaters, heat pumps, and solar heaters. Before you make your decision to buy one, you have to know how it works and be sure it is the best for you in terms of size, how convenient the heater is and the cost factor.

Generally, cost, size, conveniency and pool location are the main things to consider when buying a pool heater: Size of your spa will determine the size of the pool heater that you buy, while operating cost, conveniency, and location will determine the type of pool heater that you choose between gas, pump and solar heaters.

When considering cost in choosing the best pool heater for your spa however, it is important to know that cost difference will not be very dramatic and in the long run operating cost should just be around the same range.

A significant difference in operating cost however will depend more on how well or bad you operate and maintain your spa whether it uses a gas, heat pump or solar heater.

For example, spa maintenance measures such as covering your spa with a pool cover that prevents heat from evaporating when pool or spa is not in use will reduce operating cost of any pool heater. 

When it comes to your location or state, the best pool heater for your region may be determined by how cold or warm your state or region is during different seasons and sometimes electric rates in your state being some states have exorbitantly higher rates. 

Generally, a little warmer regions like Texas may require a heat pump because it will be economical in using electricity to maintain the ideal water temperature, rather than using a gas heater that is best for extremely cold regions like Philadelphia that requires heavy and instant water heating.

Generally, Heat pumps always work best in less colder regions: In colder regions, heat pump will overwork, use more electric units and have some difficulty heating and maintaining your spa water at some higher temperatures.   

Below are 3 types of swimming pool heaters and how they work, go through them and select the best pool heater that suits your needs.

A). Gas Heaters

Gas heaters are the most common pool heaters you will find around. I suppose, this is because gas heaters are instant and very convenient when you need your pool or spa ready within a short time.

A standard pool gas heater will heat spa water to desired temperature within 15 minutes as compared to a heat pump that takes up to 45 minutes and solar heater even longer.

Moreover, a gas heater heats your water in all kinds of weather; hot, cold or rainy, which is not possible with solar heating system that may opt you to winterize your pool during the winters.

Gas heaters use a natural gas or Propane to create fire in a heat coil exchanger, which heats water on its way to the pool.

Modern gas heaters like Hayward Universal H Series are made to be regulated between low, medium and high BTU (British Thermal Unit) or temperatures that suit the user.

When selecting a gas heater, you have to be very keen on the size of the heater in BTU: If you want to heat water in a big pool or spa, you need larger BTU Gas Heaters, the larger your pool is, the more you need a gas heater with larger BTU.

Also, it is important to know that you can use a bigger BTU gas heater in a smaller spa to increase efficiency. Most gas heaters in the market today range between 100,000 BTU and 500,000 BTU and you go with the best size for your pool.

Hayward Universal H Serie Pool Gas Heaters are among the top pool natural gas heaters and you can choose your size between 100,000 BTU to 500,000 BTU depending on the size of your pool or spa.

Lager pools from 20,000 gallons can use between 300,000 BTU and 500,00 BTU gas heaters for faster and instant heating. But it won't hurt to use 400,000 BTU gas heater on a 10,000 gallons pool, in fact it will be more efficient, instant, and with low operating cost. 

Like said earlier, smaller BTU natural gas pool heaters do not heat larger pool water faster and are best only if you have or want to put up a small hot tub and maintain hot water all the time like during the winter seasons or cold days.   

Cons of Gas Heaters

Gas heaters are made of different heat exchanger materials; Copper, Cupro-Nickel, and ASME Copper. Copper heat exchanger, which is the most common and affordable gas heat exchanger, is made of copper coils, and therefore prone to causing green copper stains in spas when chlorine is added or rises above normal level and when pH level is low in pool water.

Cupro-Nickel and Copper ASME are upgraded pool heaters and have higher resistance to chemical damage compared to pure copper heat exchanger.

Copper, Cupro-Nickel, or ASME Copper: Which is the Best Heat Echanger Material?

Gas heaters come in 3 different heat exchanger materials as follows:


Copper heat exchanger is the most common heat exchanger material and is suitable for use in any pool or spa that is chemically balanced and well maintained.

However, Copper heat exchangers have low chemical damage resistance and will be oxidized easily to cause metal stains if used over a long time without treating or removing copper metals that accumulate in your pool water.

Copper metal stain is green in colour and is formed when chlorine is added in spa water or when pH level goes down.

Due to low chemical damage resistance, Copper heat exchangers are not suitable for salt-water pools: Saltwater pools are know to have high calcium level issues and may cause calcium scales on copper heat exchanger reducing its efficiency. 

How to Prevent Copper Stains When Using Copper Heat Exchanger

To use a copper gas heater without having metal stains issues, you need to measure copper metal levels in your water at least every month and reduce copper levels when high by draining and refilling a given portion of your spa water with fresh water.

Alternatively, if draining and refilling your spa water is expensive, you can add a metal remover like ProTeam Metal Magic to remove copper metal through the filter, then backwash and rinse your filter to clean it.

You can also use Clorox D.E. Media + Filter Aid in your skimmer to filter out copper metals before entering your pool and prevent metal stains when chlorine is added or pH is low; here is more information on how to prevent or clear metal stains in your pool or spa.


Cupro-Nickel Gas Heater comes with heat exchangers made of cupro-nickel, which has a very high resistance to corrosion and staining caused by high chlorine or low pH and saltwater.

Cupro-Nickel gas heater will cost a little extra dollars as compared to the base copper heater, but with great functionalities worth your money.

Cupro-nickel gas heater are highly recommended for saltwater pools due to their high resistance to chemicals and saltwater damages. 


ASME Copper heat exchanger is made of thicker copper heat conductors and is approved by ASME. Due to its thickness, ASME copper heat exchangers are instant and heavy heaters and are the best option for commercial pools.

ASME copper heater can also be used in a saltwater pool as it is better than the the base copper model in terms of chemical damage resistance and efficiency, however, Cupro-nickel is made specifically for saltwater pools. 

How to Take Care of your Gas Heat Exchanger 

All the three gas heaters we have covered in this piece are made of pure base copper or at at least some copper elements in the heat exchanger. 

As you use your gas heater, Copper metal compounds will accumulate in your pool water.

When accumulated over time, copper like any other heavy metal is prone to causing metal stains in pools and spas when chlorine is added in water or pH is low.

Also, your gas heat exchanger is likely to have calcium buildups when calcium saturation level is exceeded, especially in a saltwater pool.

To prevent metal stains and calcium buildups in your gas heat exchanger materials whether Copper, Cupro-Nicke or ASME Copper, it's necessary to keep your spa water chemistry at per especially the pH, FC, and CH.

Remember to test and correct copper metal levels frequently in your spa water, you can use Lamotte ColorQ Pro 11 pool water test kit that measures all pool chemicals and heavy metals including Copper and Iron. 

Clean your gas heat exchanger using sutable heat exchanger cleaner like Scalzo or white vinegar on a frequent basis to remove and prevent rust and calcium buildups that reduce efficiency of gas heat exchangers.

Finally, for general improvement of efficiency and durability of your gas heat exchanger, remember to use a pool cover that will prevent evaporation in your spa when not in use.  

B). Heat Pumps

Heat pump is the second swimming pool heater we are going to look in to due it's efficiency in heating and maintaining required water temperature in a hot tub or spa.

Depending on the size of the heat pump, you need to choose the best size heat pump that will heat your small, medium and large spa water faster.

Heat pump uses electricity and that is why it's effective in heating and maintaining your spa water temperature at a cost that can be slightly lower than other types of pool heaters. 

Although slower in heating rate compared to natural gas heater, heat pumps are considered cost effective and handy when you need to maintain hot water in your spa for a long period since it does not use a lot of power to maintain water temperature. 

One big advantage of top brand heat pumps like Hayward Electric Pool Heater is that you can regulate the water temperature levels up and down to suit the users preference, and therefore apart from heating your water, it can be used as a chiller to reduce water temperature in areas that have hot and humid temperature and spa water temperatures tend to rise often. 

Before you buy a heat pump, you need to know the water temperatures that you will maintain first in your spa, then select the right size heat pump that will heat and maintain your water temperature efficiently.

Just like gas heaters, heat pumps with larger heating capacities are the best for larger pools and are fast heaters.

To select the right heat pump for your spa, use this formula recommended by US  Department of Energy to select the right size heat pump in BTU:-

 Pool Area x Temperature Rise x 12.

Cons of Heat Pumps 

Heat pumps are not instant pool heaters and are not recommended when you need instant pool warming especially in colder regions.

Heat pumps are useful; and economic to maintain a given water temperature in smaller spas and in less colder regions where less electric energy will be used. 

C). Solar Pool Heaters

Swimming pool solar heater system works by heating water that is run through small pipes in the panel, which are good heat conductors and are warmed by the Sun.

Solar heaters are only useful during the summer and only during day light when there is Sun, and cannot be used during winters and cold days.

Installing solar heater might be expensive compared to gas and heat pump, however, it has the minimal operating cost since it uses the Sun as the source of power, which is absolutely free.

Alternatively, you can use a spacial Solar Pool Cover to warm your water during sunny days or during the summer. These pool covers are made to heat your pool water using heat from the Sun and retain a warm temperature longer in your water by preventing evaporation both in the night and chilly days.   

Cons of Solar Pool Heating System

The main disadvantage of solar heaters or solar pool covers is that they are only useful when there is Sun and during the Summer. Solar heaters or pool covers cannot be used during the Winter or when there is no Sun. 

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