What About Combining Types Of Pool Heaters?

If you want to get the maximum use of your pool but minimize the heating costs you might look at using more than one type of heater.

Perhaps the most obvious option here would be to have a solar heating system backed up by a gas heater or heat pump. This would mean that you could take advantage of free solar power when it is available but still have a means of heating the pool when the weather is poor, early morning/late evening and outside the summer months.

As well as keeping heating costs as low as possible this would also be an environmentally friendly option but of course it has the disadvantage of being considerably more costly to set-up so is not a viable option for many people. However it is worthwhile looking at you much energy you could generate using a solar heating system to see if it makes financial sense. Have a look at this site to see how you might do that.

Should I Heat My Pool All Summer?

If you have a pool heater you might wonder if it is a good idea to leave it running all summer. Unfortunately there is no simple answer to this. Of course you should firstly ensure you are using a good quality pool cover to conserve heat, it will then depend on:

  • The type of heater you have – a heat pump is best used for continuous heating whereas a gas heater is best for heating the pool up quickly. With a heat pump it is best to keep the pool heated unless it is not going to be used for a period.
  • Your usage pattern – If you like to swim in the early morning or late evening it will, in most locations, be more comfortable if you use the heater even in mid-summer.
  • The climate in your area – Clearly if you are in one of the hotter parts of the country heating may not be necessary all summer but of course the weather can always vary from the norm. If you have a top of the range heat pump remember that it can probably to reversed to cool the pool when required.
  • Location of the pool – The more exposed to the wind that your pool is the more heating it will require, regardless of the air temperature, as the wind causes evaporation which cools the water.
  • Your personal temperature preference – the most important point because the whole point of a pool heater is to help you enjoy the pool.


Efficiency Of Gas Pool Heaters

The efficiency of gas heaters has improved considerably over the years and today a typical gas pool heater is between 80% and 85% efficient. This means that this percentage of the energy consumed is transferred to the pool water. The remainder is lost in various ways, mainly through discharge into the atmosphere.

However, much higher efficiencies are possible. The Jandy Hi-E2 (now discontinued) was the first gas heater to offer an amazing energy efficiency rating of 95% and you may wonder why all gas pool heaters cannot offer this level of performance.Jandy Hi-E2

Well there is a negative side to high efficiency gas heaters and this was reflected in the price of this Jandy model which was significantly higher than other gas heaters.

At the 80-85% range the wasted energy actually provides a useful function and allows the heater to operate in a simple way. The products of combustion within the heater are principally carbon dioxide, carbon monoxide and water vapor and these must be discharged safely. The unused heat exits through the stack and in doing so provides lift for the waste gases and allows them to be efficiently discharged.

As the efficiency of the heater increases there is less unused heat and the waste gases are less efficiently discharged. At a certain point this process is no longer effective and condensation occurs within the stack. The result (called the condensate) is acidic which means that more expensive, corrosion resistant, materials have to be used and fans need to be installed to vent the gases properly. In addition the condensate must be collected and disposed of safely. All of this increases the cost of the heater and its installation.

Whilst high efficiency gas heaters are often appropriate for a commercial installations it is unlikely that they will be cost effective in a residential situation. Here the heater is not likely to be used enough for the increased efficiency to offset the higher price.

It is noted elsewhere on this site that the advantage of gas heaters is that they can quickly heat up a pool but where a pool is heated constantly a heat pump is a better option. This would indicate a limited market for high efficiency gas pool heaters.

Why A Pool Cover Is Essential

If you are using a pool heater to heat your pool and you are not using a pool cover you are wasting a large amount of energy and money.

The majority of the heat lost by a swimming pool is through evaporation and this can be made worse by a windy location.

The rate of evaporation from an outdoor pool depends on the following factors:

  • pool temperature
  • air temperature
  • level of humidity
  • wind speed.

You can help reduce wind speed with a correctly sited windbreak but for owners of pool heaters it is an unfortunate fact that the more you heat your pool the higher the level of evaporation will be. A pool cover is therefore essential.

The key requirement for a pool Pool Covercover is that it is a vapor barrier. By minimizing evaporation a pool cover significantly reduces heating costs (Click Here for more information and to see savings by location). There are various types of pool covers from simple manual options to expensive fully automatic systems.

All pool covers will reduce solar gain (absorption of energy from the sun by the water) but “Solar Covers” are designed to minimize this and you should consider this when purchasing. However it is still best to have the pool cover in place whenever the pool is not in use.

Of course there are additional benefits to using a pool cover:

  • Reduces consumption of pool chemicals
  • Reduces need to top-up the water
  • Keeps debris out of the pool

So if you have a pool heater, or are thinking about getting one, make sure you have a good pool cover as well.

Click Here to see examples of pool covers

Swimming Pool Temperature

What should the temperature of a swimming pool be?

Obviously the point of installing a pool heater is to make the pool comfortable for users, and operators of commercial pools generally find that the warmer it is the more people want to use it. Having said that individual preferences vary significantly, so there is no right answer as to the best temperature.

For residential pool owners cost will be a major factor, as energy costs quickly mount as you increase pool temperature. If you use a pool cover to minimize heat loss, just increasing the pool temperature from 78° to 82°F will more than double the heating bill in most locations (see http://www.energysavers.gov).  In fact, depending on your location, for each 1°F rise in water temperature your energy costs will increase between 10% and 30%.

It is also worth remembering that if a pool is kept very warm there is a danger of bacteria and other micro-organism multiplication becoming a problem. Also chlorine-based disinfectants become less effective as the temperature raises.

If you are active in the pool 78°F may be OK as this is the temperature recommended for competitive swimming to prevent swimmers from overheating. For general use 80° – 82°F should be acceptable but you may need to go as high as 86°F for babies or disabled people.

If you use your pool most days it will be worthwhile maintaining the temperature but if the pool will not be used for several days it is best to turn off the heater. You will use less energy in reheating the pool than in maintaining the temperature.

Are Electric Resistance Pool Heaters Worth Considering?

You can buy electric resistance heaters to suit all sizes of pools and spas but they are not as popular as gas heaters or heat pumps.

Coates offer a large range to cover virtually any residential or commercial application and are a good buy if you want this sort of heater but there are only a limited number of situations where they are advantageous compared to other types of heater.

Coates Heater Company has been manufacturing pool heaters since 1955. They still aim to build quality and reliability into every model to provide years of hassle-free performance.

If you have access to natural gas a gas pool heater will be cheaper to buy and much cheaper to run (although a propane heater will likely cost more than an electric heater).

A pool heat pump is the cheapest way of heating a pool and is the route you would normally take if you want (or need) to use electricity to heat your pool or spa.

Looking at the Coates CHP Range (24 – 30 kw) which you might use for a residential pool, these can be installed indoors or outdoors, are available for single or three phase power supplies and feature a digital thermostat for accurate temperature control. Flow rates are between 20 and 80 GPM and have a built in switch to prevent operation when there is no flow. An all stainless steel tank for long life and corrosion resistance is also standard.

The advantages of an electric resistance heater are:

  • Provides its quoted heat output regardless of the conditions – The same applies to a gas heater but a heat pump becomes less effective as the temperature drops and they may not work at all in cold conditions.
  • Pollution free – There is no need to worry about exhaust gases or air flow, which means that there is more flexibility in locating an electric resistance heater making it less obtrusive  and it may be safer if there are children about.
  • Mature Technology – the device should run reliably for many years.

The disadvantages of an electric resistance heater are:

  • Costly to run – running costs many times that of a heat pump or a natural gas heater.
  • Not as powerful as a gas heater – The Coates heaters range from 1.5 to 300 kw (for comparison purposes this is  5k – 1025k BTU) although the high powered ones are for commercial applications. The models for a residential pool are about 30kw which is about 100k BTU.
  • Environmentally unfriendly – unless the electricity is generated by renewable means.

If you have a spa that you want to use in colder weather and do not want a gas heater then an electric resistance heater may be ideal. However for heating a residential pool this sort of heater is unlikely to be a good choice.

To see the Coates pool heater range at Pool Supply World – CLICK HERE

What Size Pool Heater Do I Need?

A simple question but there is no simple answer.

Gas pool heaters typically range from 100,000 BTU/hour to 400,000 BTU/hour and all will heat your pool. Larger heaters will warm a pool faster and are slightly more energy efficient but, of course, they cost more.

The main alternative electric heat pumps are much less powerful 100,000 – 130,000 BTU/hour and cost more but they are very energy efficient  and therefore cheaper to run.

Below is a table giving some guidance based on the capacity of the pool or the surface area but this is very just a general guide. Much will depend on:

How you will use your pool heater

Will you want your heater to heat up your pool as quickly as possible at intervals or will you keep it heated all the time during the season. If the former you want the highest capacity heater you can afford so that the pool is ready for use quickly when you need it. If the latter you need a lower capacity energy efficient heater which keeps the pool ready for use at the lowest cost.

The location of your pool

Wind is the big enemy here. It will cause more evaporation which causes the pool to lose heat. So if your pool is in an exposed position your pool heater will have to work harder.  You also need to consider the lowest air temperature in the months you want to heat the pool and therefore the temperature raise required.

Your use of a pool cover

Use of a pool cover when the pool is not in use will dramatically reduce heat loss and therefore the demand on your pool heater.

Below is a simple table to give an indication of the size of gas heater that will be appropriate.  If you want to undertake a more detailed calculation have a look at this page.

Size Heater Gallons in Pool Sq. Ft. Surface Area of Pool
100 – 200 BTU heaters 1,000 gals to 10,000 gals up to 300 sq ft
200 – 300 BTU heaters 10,000 gals to 20,000 gals up to 500 sq ft
300 – 400 BTU heaters 20,000 gals to 40,000 gals up to 800 sq ft
400 BTU heaters 40,000 gals to 80,000 gals up to 1200 sq ft

In general it is best to work out what you think you need then get something slightly larger as, apart from the higher purchase price, there is no harm in having a more powerful heater than you need.

If you want to heat your pool quickly you should go for a gas heater. However, before doing so you should look at the running costs compared to a pool heat pump as it may be that using a heat pump to keep the pool heated for longer periods would be more cost effective.

One of the major manufacturers Raypak has an interesting program for sizing a heat pump and showing the savings you will make. Click Here to visit this program,

Solar Pool Heater – A Viable Option?

A solar pool heater uses energy from the sun to heat your pool – which of course is free and environmentally friendly.

It has other advantages too:

Can be installed by pool owner – Solar heating kits are available that suit both above ground pools and in ground pools and are easy to install. There is no need for qualified gas contractors or electricians. The main issue is the installation of the solar collectors which can be on a roof or on a frame angled towards the sun.

Little maintenance – Once installed the system requires little maintenance which compares favorably to gas and electric heaters.

Long lasting – A solar pool heater will last a long time and hence maximize the return on your investment. 15 year guarantees are available.

Solar Heater Diagram

Solar Heater Diagram

However there are a number of disadvantages to consider:

Needs large area for solar collectors – As a rough guide the area of the solar collectors will be need to be 50-100% of the surface area of the pool. Even with a small pool this can be a significant space requirement and may spoil the appearance of the pool surroundings.

Not as powerful as gas heater or heat pump – Even in ideal conditions the heat output from a solar pool heater will not match those of gas pool heaters and electric heat pumps. Solar heaters are not able to raise the water temperature as much as gas or electric heaters and may take several days to achieve the sort of temperature raise other types of heater could achieve in a few hours (so a pool cover is essential).  Solar heating will still work on overcast days but the output will not be as high as on a sunny day.

Dependent on Local Conditions – The effectiveness of a solar pool heating system will depend on average temperature for the location, wind factors, the angle and orientation of the collectors and the solar exposure. To work at their best the solar collectors need to be facing south and not be shaded by trees or anything else at any time of day.

Can be expensive – The cost of buying a solar pool heater system depends on the area of solar collectors you need. For an in ground pool it can work out more than the cost of a gas heater.

What is available? -If you have an above ground pool you can buy small space saving devices and ground standing solar panels which you position in a sunny spot and pump the pool water through them. In the right location they can be effective but if you have a larger pool you need much larger panels which will ideally be roof fitted. You can buy a base system and then add-on extra panels as required for the size of your pool.

Whether a solar pool heater will work for you really depends on your location and how long you want your swimming season to be.  If you can locate the solar collectors to get best results and are not looking to extend your season into the colder months then a solar pool heater is well worth considering. You might also consider a solar heater in addition to another form of heating so that you can make use of the free heating when it is available and back up with a gas heater or heat pump when it is not.

Pool Supply World have a range of solar heaters for above ground pools. CLICK HERE to see their range. You might also be interested in the range available at SPP.


Pentair MasterTemp

The Pentair MasterTemp series is a range of low NOx gas powered pool heaters with models from 175k to 400k BTU. There are models for both propane and natural gas including two “heavy duty” models for the latter.

To purchase a Pentair MasterTemp from Pool Supply World – Click Here.

Pentair MasterTemp Gas Pool HeaterDespite its functionality this pool heater is compact. It measures only 21″ x 21″ x 28″ (L x W x H) so is easy to install even where space is limited. A rotating digital display ensures that the controls are easy to see and use regardless of how the heater is positioned. The cabinet is a tough composite material which is not affected by heat or the weather.

However, the key selling points are:

  • It is certified for low NOx emissions so can be used where NOx emission restrictions are enforced.
  • It has an efficiency rating of 84% (using the standard copper heat exchanger) making it one of the cheapest to run gas heaters.
  • Heats up fast due to its fully pre-mixed system – which also contributes to its efficiency – so no waiting around for your pool to heat up.
  • Easy to operate – required temperatures can be set at the touch of a button and a digital display shows the water temperature, whilst five LEDs show you what is going on.

Pentair MasterTemp Brochure

There are also two “heavy duty” models which use a cupro-nickel heat exchanger. This stands up better to heavy use and poor pool chemistry but reduces the efficiency to 82%. ASME versions are also available for commercial use.

The Pentair MasterTemp heaters have a series of features designed to ensure safe operation but you can’t please everybody. For instance there is a factory set maximum water temperature which annoys some users (there are discussions online about how to get round this). However, overall this heater is a good choice if you need a low NOx gas heater.

Our recommended supplier is Pool Supply World who offer good prices which include shipping (often an expensive extra).

CLICK HERE to see their prices.

Other Pentair Pool Heaters.

pentairpool.com/… pumps/mastertemp heater

Pool Heat Pumps – The Best Option?

Pool heat pumps are an increasing popular way for heating a pool. They are cheap to run and environmentally friendly but do have some disadvantages.

What is a Heat Pump?

A heat pump is a device for moving heat from one location to another. In the case of pool heat pumps heat is taken from the surrounding air and transferred to the pool water. The efficiency of air source heat pumps, like pool heaters, declines with the air temperature and ice formation is a problem at low temperatures.

A heat pump providing heating for a house is likely to be a ground source heat pump where the heat is taken from the ground using a length of well buried pipes. These have the advantage of being able to work at low temperatures but are expensive to install.

There are also water source heat pumps which take heat from one body of water and transfer it to another. These are rarely suitable as pool heaters but there are models available designed to take heat from a swimming pool to heat a spa.

How do Heat Pumps work?

We are all used to refrigerators and air conditioning units which work in the same way except they are used for cooling rather than heating. In fact the top of the range pool heat pumps usually have a reverse mode in which they cool the pool.Heat Pump

Heat pumps transfer heat by circulating a refrigerant through a cycle of evaporation and condensation. An electrically powered compressor pumps the refrigerant between the two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed en route to the other coil, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.

With any other type of heater it is impossible to have an efficiency in excess of 100% because energy output cannot exceed energy input. In practice, for example, most gas pool heaters are 80-90% efficient. The key point about a heat pump is that because it does not actually generate heat, the amount of energy (heat) produced is much greater than the energy (electricity) used. So even though a pool heat pump is powered by electricity it is still much cheaper to run than a gas heater.

How efficient are Pool Heat Pumps?

The efficiency of pool heat pumps is measured by their COP (Coefficient of Performance). This is a measure of how many units of heat energy are produced for every unit of electricity used. For a residential pool heat pump a value in excess of 5 is good. However a word of warning, the COP varies depending on the air and pool water temperature and relative humidity. It is normally measured at 80 degrees for air/water and 80% RH but this is not a defined standard.

Pros and Cons of Pool Heat Pumps


  • Cheap to run
  • Eco Friendly
  • No emissions


  • More expensive to buy
  • Less powerful than gas heaters
  • Not so good in cold conditions

Should you buy one?

If you want to extend the season during which your pool is usable and you heat the pool most of the time then a heat pump will be your best option. If you only want to heat your pool occasionally then you might be better with a gas heater because it will be able to heat the pool faster and its lower purchase cost will offset the higher running cost.

Click this link for information on Pool Heat Pumps that are available.