What is pool heating?

For pool owners who live in colder or inconsistent climates, you probably don’t have the luxury of using your pool all year-round unless you’re keen on ice baths in the middle of winter. You don’t need to settle for only 4-5 months of pool use each year, there are a few solutions to significantly extend your swimming season. There are three main types of pool heating: gas, electric and solar. Each has their pros and cons, here are some factors you should consider prior to selecting the one for you.  

The surface area of your pool

Spas and smaller pools will heat quickly with gas heating, larger pools are heated more efficiently with electric heating. Solar can be great for small or large pools, depending on your catchment area (where solar panels will go) and your climate. The larger your pool, the bigger and more powerful the heating source will be, which will add to the install costs.  

Climate

If you live in an area with little sun exposure or an extended wet season, solar may not be your best option. What is the average temperature in the coldest month you plan to swim in? If you’re hoping to extend your swim season from Spring to Autumn, what is the average temperature in September and May? Average temperature and your ideal pool temperature will help with selecting the size of your heater.  

Cost to run

Solar is often the cheapest to run because it relies on energy from the sun (as the name suggests) to heat your pool. Often the only added cost to this is running your solar pump when you’re heating your pool. Electric usually comes in second place in terms of cost to run, followed by gas, depending on the price of gas in your area and which type of gas you go with (natural vs. LPG). The average cost of installing pool heating can be anywhere between $2,000 up to around $10,000.  

Efficiency

How efficient each heating method will be, depends on the size of your pool. While gas can be costly, it works well for smaller bodies of water because it heats very quickly, so you’re not running it for as long as you would with solar and electric. With a medium to larger pool electric will heat your pool up to whatever temperature you desire, though it may take a little longer, it is much cheaper to do so than gas. Solar is the most energy efficient method of heating, though is often restricted to increasing pool temperatures by 6-10 degrees. If you’re hoping to swim on a 15-degree day, your pool might reach a comfortable 25 degrees.

What is solar heating?

Solar heating uses energy and heat from the sun to heat your pool water. Solar works by circulating water through the series of rubber tubes on your roof, heating the water and then returning it to your pool. Ideally, a solar system should be set up independently of the filtration system with a separate pump which means you can heat your pool 12 hours a day without having to run your pump and filter for the same amount of time. On a new installation, a solar controller will be installed, often mounted to the wall near your existing equipment. Solar controllers work by measuring the temperature on the roof, comparing it to the temperature of the water and turning the solar pump on and off as required automatically until the water reaches the preset temperature. Solar heating also works best in areas with close to year-round warmth and sunshine. Solar pool heating can extend the swimming season for around four to six months if you live in Melbourne. During the warmer months, solar heating can add on average 6-10 degrees to your pool temperature. Below we have listed some factors you should consider if you think solar may be the best heating option for you.  

What factors affect solar heating?

There are many elements that can influence how efficient solar heating will run on your pool:   Roof surface area Ideally, you want the equivalent of 100% of the pool surface area in solar collectors on the roof. At the very least, 80% or above should do fine, but this depends on your location. If you’re up north of Australia, 80% will be more than adequate. In cooler climates, more is better.   Roof orientation North facing roofs are the optimal place for solar heating in order to maximise heat collection to heat the pool. If there is not enough room on the north side of your roof, a west facing or flat roof installation will provide a sufficient level of heat generation.   Roof material Metal roofs are the most efficient at transferring heat into the solar collectors; with tiled roofs being the next best option. Dark coloured roofs are the most solar friendly, as they collect more heat than lighter colours. Slate roofs are not ideal due to troubles with adhesion, as it is a porous material and also doesn’t retain heat very well.   Colour of solar tubing Like roof colour, darker colours collect heat better than lighter colours, so while it may be tempting to match your solar collectors to the roof colour, your best option is to go with black.   Shade You will need to consider the amount of sun your solar collectors will receive. Although north facing collectors usually receive the most amount of sun, a large tree or a multiple storey building on your north side may impact the amount of time your collectors sit in the sun. In this case, your optimal catchment zone may be north-west or west. If your pool receives little sun, this may also impact how effective solar heating will be for your pool. Pools in the shade will take longer to heat up and may not reach the desired temperature. If you’re in a situation where your pool is in the shade, but your collectors are not, you may need to add additional collectors to decrease the deficit.   Wind If you live in an area with high winds, your pool is more likely to lose heat faster. You may need to increase your solar collector area in order to reach and maintain desired temperatures.   Pool cover If you have a thermal pool cover, this can help in creating and retaining heat within your pool. We’ll touch on this in greater depth later.  

Solar options

There are a few options available when looking to purchase solar pool heating.   Flexible and rigid tubing Solar comes in either flexible or rigid tubing. Flexible tubing allows for manoeuvrability around chimneys and any other roofing fixtures like satellite dishes without compromising on surface area. Flexible solar tubing often comes in two types of ends: flat and looped. There is no loss or gain of efficiency, flat ends were designed for the consumer who thinks the looped ends are somewhat unsightly. As the flat ends are considered a premium look, they cost on average $5-10 more per square metre. You can also get flexible solar tubing in a range of colours if you’re looking to match it to your roof. Black, grey, brown and green are common and available, most people stick to black for optimal heat generation, it is also the cheapest due to mass production. If you choose a colour other than black, you may need to increase your solar collector area to counterbalance the deficit in heat generation. Rigid panel solar collectors are designed to be sturdier and eliminate weak points in joins, with thicker tubes to fare better against wildlife. Rigid panels often only come in black and are considered a premium product, so an increase in cost applies, on average cost will double.   Glazed collectors You can also get what is referred to as glazed solar collectors, which are often made of a copper tubing on an aluminium plate, covered with a tempered glass cover. By combining these materials, heat generation increases which can do a better job of heating your pool in cooler but sunny months (think about how hot your car gets in the sun even in winter). Glazed solar can be used year-round and carries a premium price tag.   Wired and wireless solar controllers Solar controllers also come in two options, wired and wireless. Wired controllers have roof and pool temperature sensors, allowing information from both to be sent to the unit. The roof sensor should receive similar sun to the solar collectors, however, does not need to be in contact with them. The pool sensor should be placed along the suction line prior to the solar collectors. The wireless system has the same principle, except as the name suggests, it has a wireless heat sensor. When the pool sensor reaches the preset temperature on the controller, the solar controller will go into energy saving mode. Energy saving mode for most controllers will switch the solar pump off for a period of time.  

I’ve heard about solar cooling, what does this mean?

Solar cooling works the same as solar heating, except you run your system at night which will cool the water down. If you live in warmer climates where your pool gets too hot to be refreshing, solar cooling can work well in achieving your preset temperature.  

Cost

A solar heating system based on a 50,000L pool will cost around the $5,000 mark for the initial install. Around a third of the install cost covers labour, as solar often takes longer to install than an electric or gas heater. Solar is often the cheapest to install and to run in comparison to gas and electric. While it is the cheapest, it is weather dependent and you may not always achieve your preset temperature. Solar heating will cost approximately $100-200 a year to run.  

What is electric heating?

Electric heaters, also known as heat pumps, use the same technology as your fridge and air conditioner, except in reverse. Heat pumps do not create heat, they use electricity to take heat from the ambient air temperature, or from underground, to heat up the pool water and can function in weather as cool as 7 degrees. Heat pumps are a great option for year-round heating of your pool. To break it down, heat pumps have a fan that draws in the air surrounding it, passing it through an outer evaporator air coil. The outer evaporator air coil uses the outside air to heat up the refrigerant liquid inside it, which is then transformed into a gas. The gas is then passed through a compressor. The compressor works to heat the gas further, prior to passing through the heat exchanger. The heat exchanger works to transfer heat from the gas to the pool water, increasing the temperature of the water passing through by 3-5 degrees. As the gas passes back through the condenser coil, it cools and returns to a liquid before travelling back to the outer evaporator air coil, where the process starts over. A less common type of heat pump is the ground source heater. They work similar to air source heat pumps, though as the name suggests, sources heat from the ground rather than the ambient air temperature. They are often difficult to retrofit to an existing system without doing major landscaping work and are more suitable for heating your home (hydronic heating) rather than your pool.  

Are heat pumps efficient?

Heat pumps are extremely energy efficient. They can produce 6-14 kilowatts of heat from just 2 kilowatts of energy. Energy efficiency in heat pumps is measured by the coefficient of performance (COP). The greater the COP, the more efficient the heat pump. As there isn’t a standard COP assessment for every heater, COP should be used as a guide when looking to purchase a heat pump. Each heaters COP can vary depending on certain variables. For example, a heater working on a 20-degree day will have a greater COP than when it is operating on a 10-degree day. The coefficient of performance is measured between 3-7, which means your heater has an efficiency rating of between 300-700%. So if your heater has a COP of 6; for every unit of energy passed through your heat pump, you get 6 units of heat out of the heat pump. Heat pumps have come a long way over the years to increase energy efficiency and are still getting better and better. Higher efficiency heat pumps now have scroll compressors instead of reciprocal compressors. A reciprocal compressor acts as a piston or hammer to compress the gas in the chamber. Though it is effective, it is not as efficient as a scroll compressor. A scroll compressor works to compress gas within the chamber, using two spinning archimedean spirals (think time travelling portals and optical illusions, that spinning wheel you see that looks like it’s never ending). Two archimedean spirals constantly compressing gas just by moving one spiral in a circular motion is much more efficient than a constant hammer. Keep this in mind when looking to purchase a heat pump if you’re concerned about efficiency and more for your money.  

What factors affect heat pumps?

Most heat pumps in Australia range from 60 to 300 kilowatts of energy output. Consider the following factors prior to purchasing a heat pump:   Weather Most heat pumps will operate year-round depending on your location. If you live in an area where the minimum temperature sits below 7 degrees, your heat pump probably won’t work effectively to heat your pool. For Victorian, South Australian or Hobart residents, a heat pump with a heating capacity of around 21 kilowatts and COP of 5.5 providing 115.5 units of heat for an average sized pool (around 40,000L) should be sufficient. Further north of Australia, the same size pool could achieve the same results with a 13-kilowatt heater with a COP of 5.5 and output of 71.5, because of the higher minimum temperatures.   Size of your pool The surface area of your pool is what most heaters go by when measuring the heat capacity required for your pool. Victorian, South Australian or Hobart residents with a 25 square metre pool will find a heater with a heating capacity of 13 kilowatts and COP of 5.5 will achieve the same results as their next door neighbour with a 40 square metre pool using a 21-kilowatt heater with the same COP. As a general rule, the larger the pool, the greater the heating capacity required.   Desired temperature If you have a small pool but prefer a higher swimming temperature, choose a heater with a higher heating capacity. If you’re concerned about efficiency, keep an eye on the COP as heating capacity increases. If heating capacity increase and COP decreases, your heater is not going to operate as efficiently as smaller heaters, so it may cost you a lot more to run a bigger heat pump, for similar results.   Shade A pool that does not get a lot of sun will most likely have a lower starting temperature than a pool in the sun, so your heater may need to run for longer to compensate. Similarly, a heat pump in the shade may have a lower air temperature surrounding it, so its ability to heat your pool can be decreased. It is ideal to keep your heat pump in an area receiving sunlight to increase heat output.   Wind High winds can affect the air temperature surrounding your heat pump which affects your heat pumps heat output, although this impact is more often than not quite minimal. Winds can also increase heat loss from the pool water.   Location of pool/heat pump (indoor vs outdoor) If your pool is outdoors (as most are) and your heat pump is too, the outside air temperature is much more variable than the temperature indoors. So a pool and heat pump located indoors will probably take less time to heat up than a pool located outdoors on an overcast day.  

Cost

Heat pumps start at $6,000 for a small pool, up to around $10,000 for a new energy saving system suited to larger pools. Depending on how much you want to extend your swim season, you’ll probably be paying around $500-1,000 a year to heat your pool, in conjunction with a pool cover. It’s much cheaper to run a heat pump to heat a pool than it is to run a gas heater if you’re hoping for a year-round swim season.

What is gas heating?

Gas pool heaters work very similarly to your indoor gas heaters, they burn gas to create heat which heats the water passing through, just like your indoor heater would heat the room it’s in. The two main types of gas used in gas heaters are natural gas and liquid propane gas (LPG). Gas heaters can operate all year round and do not rely on the outside air temperature. They are a very effective method of quick pool heating, so are great if you don’t use your pool very often. So how do they work? You pump sucks water from your pool through the filter, before sending it through the heater. The heater has a blower and a burner, used in conjunction to set off hot gas, which then heats the copper piping the water is pumped through. Cold water goes in, hot water comes out. Gas heaters may seem to work similar to electric heat pumps, and they do internally; a gas is used to heat up the pipework that your pool water flows through. The main difference is gas heaters do not rely on ambient air temperature to operate effectively, as heat pumps do. Also, the burnt gas leaves the heater via a flue, as opposed to the gas in heat pumps which turns back into a refrigerant after use. It can take a few hours for gas heaters to completely heat your pool to the desired temperature, and they are often the fastest method.  

Are gas heaters efficient?

Most gas heaters operate between 85-95% efficiency, which means for every 100 units of thermal energy produced through the burning of gas, the heater will produce 85-95 thermal units of heat. In terms of getting to your desired pool temperature, gas heaters will get there the fastest, but they are also the most expensive. While they have come a long way in increasing efficiency over the years, they are the least efficient type of pool heating, with an average coefficient of performance of 0.8-0.85. Depending on the cost of gas in your area and how often you swim, it may be easy to overlook the COP in favour of a quickly heated pool every now and then. Adding a thermal pool cover will help with retaining heat in the pool.  

What factors affect gas heaters?

Not many factors will affect how a gas heater operates. However, consider the following factors prior to selecting a gas heater to ensure you have the right size:   Weather Gas heaters do not rely on the weather to work efficiently as heat pumps and solar heating systems do. However, if you live in a generally warm climate with only a few mild or cooler months, a small gas heater should do just fine. If you live in a climate with cold winters, go for a larger gas heater so you can heat your pool quickly when you choose to use it. It will not matter if your gas heat is located in the sun or the shade, but should not be placed near your barbeque.   Electrolysis Gas heaters have what is called an anode rod, usually made out of aluminium, magnesium or zinc. Anode rods are used in gas heaters to prevent corrosion of the tank metals, so increases the lifespan of the tank. How does it prevent corrosion? The anode rod has a higher negative electrochemical potential than the wall of the tank, so it begins to corrode first. After years of running, the anode rod will be completely corroded, which is a good thing because it means it has done its job. It’s best to check it every three to five years so you can replace before it’s completely corroded.  

Cost

The cost of a gas heater will cost on average $6,000 for an average sized pool, and is the quickest way to heat your pool. Spa heaters are cheaper since they are smaller and heating a lesser volume of water. Annual running costs for your gas heater will depend on gas prices in your area, generally anywhere up to around $2000. Installation requires a gas plumber and may add to the cost of our installation.    

What are pool covers?

Pool covers are like a shield for your pool, and have varying roles and outcomes depending on the type. Almost all pool covers will also help to prevent water loss through evaporation, so not only will you save on heating costs, but also the cost of chemicals and the time used to run your equipment. You can get a cover designed to be used in conjunction with your pool heating system to keep heat in your pool and run your heating less than without it. You can also get pool covers that heat your pool and also retain heat within your pool. Below we go through the two types of covers closest related to pool heating:  

Thermal pool covers

A thermal pool cover (also known as a pool blanket) can assist with retaining heat within your pool. They work by using a high quality multi-layered, foam-based material to prevent heat from your pool escaping into the atmosphere. Thermal covers also keep out debris and sunlight, which are the main factors for algae growth, so keep your cover on when the pool is not in use, keep your chlorine levels up and you should be algae-free. Thermal pool covers will reduce heat loss on average around 75%, saving your heating run time and keeping your cash in your pocket. Generally thermal blankets are initially more expensive than bubbles covers, though they usually last twice as long. If you have a pool heater, a thermal cover is most likely your best option.  

Bubble/solar pool covers

Bubble covers are what probably comes to mind when you think of pool cover, they have been around for a long time. Bubble covers have multiple purposes and are a great allrounder cover. Made of polyethylene, bubbles are moulded into the cover to create and retain heat. To create heat, the air in the bubbles heat up in the sun and transfer that heat directly from the cover to your pools water, similarly to how solar works. With a bubble cover, you can add around 8℃ to your pools temperature. Bubble covers are able to retain heat by acting as a buffer between the warm pool water and the cold are outside, preventing heat from escaping from your pool so easily. In summer, it’s best to not leave your bubble cover on 24/7, because you can overheat your pool, so your chemicals may not work optimally. If you have no pool heating system but would like to benefit from the sun's warmth, a bubble cover may be the best option for you.  

What factors can affect pool covers?

Weather Like most pool heating methods, cold weather can limit how well your cover will heat and retain heat in your pool. It may be best for you to leave your pool cover on for the majority of winter. On the other end of the spectrum, in summer your pool can get too hot, so make sure you take your cover off regularly in summer to let your pool cool off as well as yourself!   Pool volume/surface area As with any heating method, the larger your pool, the longer it will take to heat up. The larger the surface area of your pool, the more heat you can potentially lose overnight. Pool covers are no different, however, a well-fitted pool cover will reduce heat loss and increase heat retention during the swim season.  

Cost

Bubble covers are the cheaper option, on average you’re looking at around $10-22 per square metre, depending on the quality. For a thermal blanket, $35-45 per square metre is on average what you’ll find, again you’ll pay more for quality. Rollers start at around $500 for your basic plastic roller, however, you can also get stainless steel, chair, inground and automatic rollers that can add sophistication to your outdoor living area. Installation is mostly the charge of labour, anywhere from $80-160 per hour is expected.