Swimming Pool Heating Systems
Article was written by Gregory Grochola (physicist) - 29/07/2025
This article, as well as our article on solar pool heaters and pool heat pumps, goes through the best swimming pool heating system options available in Australia, including some clever ones that are very cost-effective, but you might not be aware of. Read on...
Table of ContentsClick Heading Titles to Navigate Up or Down
Unless you live in the Northern States, and/or only swim in the summer months just to cool off, and/or your swimming pool has very favorable heating loading factors, you'll definitely want an active swimming pool heating system to take full advantage of the investment you've put into your pool.
Heating a pool doesn't have to be costly if done right; this article summarizes three main ways to get a higher pool water temperature, namely; utility-based pool heating systems, poly solar heating systems, and solar PV heat & pump hybrid systems.
At a fundamental level, the temperature of an outdoor body of water is dependent on two competing factors: energy-in vs. energy-out. Most people focus on the energy-in heating part, but did you know that preventing heat loss is critical and almost more important than putting heat in? We'll get to this fourth method of heating a pool below, as there are some clever ways to minimize heat losses, and I don't mean just a solar blanket.
2.1.1 Solar PVC Strips/Mat/Tube Roof Collectors
PVC strip collectors (also called solar mats or tubes) are made by extruding a long cross-section of tubular water channels. They are typically mounted with strips going across the roof with their main header pipe (also called the manifold or feed pipe) going up/down the roof. The PVC material typically has a softening agent (a plasticizer) which makes the strips flexible. Individual tubes are joined to barbs on the manifold and are either glued in or held in place using mechanical clamping means.
2.1.2 Solar Pool Heating Roof Panels
Solar pool heater panels are a one-piece construction, blow-molded HDPE plastic panel, having a large internal set of water channels, with a low pressure drop across them and fast turbulent water flow characteristics.
2.1.3 Hybrid Tube Roof "Panels"
These hybrid "panels" are typically made from extruded PP or PP blends with channels that are either joined together or in a loose arrangement, installed with tube water channels going up the roof. The channels are welded or mechanically attached to a main header pipe going across the roof.
2.1.4 Enclosed Solar Pool Roof Panels
Enclosed solar pool panels are basically polymer collectors that are covered with a glazing material (glass or transparent plastic). The glazing material increases the efficiency of the panels during adverse heating conditions like spring and autumn, which can involve cold and windy, but yet sunny days. These types of collectors are best reserved for heating premium indoor pools where the water temperature is substantially higher than the air temperature during winter.
2.2.1 Electric Heating Element
This is basically a bar heater or heating element, immersed in flowing water. Electricity is used to heat the element and in turn the water. Typically used to heat small, highly insulated spa pools, they are the least efficient means to heat a pool or spa. Their COP (Coefficient Of Performance) factor (energy in to energy out ratio) is 1.0 - meaning for every 1 kWh worth of electrical energy you put in, you get 1 kWh worth of thermal heating. Note, deceptive marketing could also state these heaters are 100% efficient. While this is technically true, they remain the least efficient of any pool heating option.
2.2.2 Electric Heat Pumps
Heat pumps work by using electricity to "pump" or transfer heat from surrounding air into the pool water. They work on the same principle as air conditioners but in reverse. They can have average de-rated COP (Coefficient Of Performance) factors as high as 4 to 5. This means for every 1 kWh worth of electrical energy you put in, you get 4 to 5 kWh worth of thermal heating out.
2.2.3 Gas Heaters
Gas heaters basically burn domestic gas to heat a heat exchanger with flowing water, in turn heating the pool water. They have typical efficiencies of 87%; meaning of the total energy obtained from burning gas, 87% will get transferred into the pool water, the rest will get blown out with the hot exhaust air.
The combination of solar electric panels (PV panels) and heat pumps
could also be classed as solar-based heating systems. These systems work
by firstly, harnessing electric energy via the solar electric panels,
which is then used to run a heat pump to warm the pool. Modern PV panels
are typically only 18% - 23% efficient, as compared to a modern solar
thermal pool panel which is about 80-90% efficient, however an efficient
heat pump with a COP factor of ~5 can make these systems close to ~100%
efficient (with regards to the amount of the solar energy collected and
transferred to the pool), which is comparable if not slightly better
than the best polymer solar pool heater systems.
The main issue with these systems is the large upfront costs which lead
to long payback times. Of course, it should also be taken into
consideration that PV panels will produce electricity during the
non-pool heating season, unlike solar thermal collectors.
When considering a swimming pool heating system, one of the first and most important things you'd want to do is understand how your pool's heat losses (and solar gains) affect the pool's overall water temperature. We've produced accurate and sophisticated pool water temperature simulation algorithms over the years to help you. It's critically important to understand how much energy you'll need to bring the water temperature up to a level you're comfortable with BEFORE considering the type of pool heating system you'll need; as you may find that very simple measures might bring your pool up to a temperature you're happy with. Alternatively, you might find that some heating systems simply are not capable enough to provide (or are too expensive in providing) the swimming season you desire.
To help you understand heat loss factors and what we can do to minimize them, below is a description of the four fundamental heat loss mechanisms:
Evaporation is a large factor, a lot of heat is carried away by water molecules. There are a few clever things we can do. Firstly, a transparent solar pool cover lets light through while forming an insulating layer to prevent evaporation. Note, a lot of people believe that if they can't cover all the pool's total water surface area, that a solar blanket might be compromised and that it's not worth it. Actually, that's not at all the case; technically if you can only cover half the pool's water surface you still get half the benefit, with the caveat that water can't wash up on the blanket as this defeats the purpose of preventing evaporation.
There are a couple more ways to prevent evaporation; the other way is of course wind sheltering a pool by planting shrubbery or erecting wind blocks. In fact, wind speed across a water's surface is a governing factor in the evaporation equation.
Evaporation is also dependent on the water's surface temperature, and I mean surface temperature, since some people run a pool heating system but the system they run doesn't have enough flow to push and mix the warm water deeply down into the pool's depths. It's critical to remove the hot layer that is generated during the day, so that lower temperature pool water comes to the surface overnight, effectively reducing evaporation.
Lastly, don't forget the ground around the pool; is it grass? As water can evaporate from the soil surrounding a pool which will also cool a pool. Paving around a pool would have a small effect on the pool's water temperature, but only a small effect. Still, you might want to consider a darker paving surface.
This loss factor involves thermal infrared energy being emitted from the water's surface into the cold, clear sky. A polyethylene (PE) blanket mostly transmits infrared radiation, hence it doesn't help much here, and of course the surface of the PE blanket itself warms up and emits infrared energy from its surface. Again, mixing a stratified pool will help a lot, so make sure you run your filter in the afternoon to mix the water for nighttime. But apart from hoping for cloud cover, there is not much we can do to reduce this factor.
The third of the main heat transfer mechanisms, convection happens when air molecules touch the water's surface. Heat will be lost and conducted to the cooler air molecules - if (and ONLY IF) the air molecules are cooler than the pool water surface. This is not always the case... as an aside, did you know there are some areas in Australia that get such hot air that this factor is actually a positive heat gain? Yes, sometimes hot air blowing over your pool will heat your pool!
But mostly, convection cools a pool, and again, a pool blanket will largely prevent this, but not completely, as cold air still touches a solar blanket. And again, the water's surface temperature has a large effect on this factor; the more stratified the pool is the worse this factor gets, especially at night. Lastly, again, wind speed across a pool's surface increases this loss factor.
Conduction (through the walls and floor of the pool) involves the slow loss of thermal energy by the outside of the pool being in contact with the soil. There are a couple of factors that can increase this factor: wet soil, which boosts conduction, and of course wind exposure for an above-ground pool. Soil mostly acts as an insulator, but it also stores a lot of heat energy, so when you install a new swimming pool heating system, the ground around the pool needs time to warm up as well.
Lastly, you should also consider solar gain. In fact, did you know this is the single largest source of heat for an unshaded, outdoor swimming pool? It's a larger source of heat than an actual solar pool heating system! This is because the vast majority of the solar energy falling on a pool's surface is absorbed inside the pool. The darker your pool's side walls and floor, the better. If you have a North-facing wall next to your pool and you paint it a light color, this will significantly boost the reflection and hence solar energy gain going into your pool.
If you can, you should remove all shading on a pool. You should also be aware there are some poorly designed silver-back "solar pool blankets" being sold. These are terrible when it comes to heating your pool; they reject sunlight and will actually cool your pool compared to more transparent covers.
- Budget Friendly to Purchase: Depending on the type of system installed.
- Low Operating Costs: Essentially almost free to run comparatively.
- Environmentally Friendly: Has a near-zero carbon footprint during operation.
- Long Lifespan: Poly solar collectors can last anywhere from 15-30 years depending on the type of collector.
- High Initial Upfront Cost: Some premium collectors are expensive to purchase.
- Weather Dependent: The system's effectiveness is limited by the amount of sunlight. Solar is not an on-demand type pool heating system.
- Requires Sufficient Roof Space: Often almost 100% of the pool's surface area is used, sometimes more or less depending on specifics.
- Consistent Performance: Can heat the pool over a wide range of weather conditions, unlike solar heaters.
- Simpler/Cheaper to Install: Installers love them as they don't require climbing on a roof.
- Rapid Heating for Gas Heater: Can bring a pool up to temperature quickly.
- High Initial Cost: Depending on the unit. Gas heaters are cheaper to purchase initially.
- High Running Costs: Depending on heating loads and the type of unit used. Gas heaters are very expensive. Heat pumps are more efficient but nowhere near as efficient as solar.
- Noise: Heat pumps can generate noise.
- Lower lifespan: Both gas heaters and heat pumps have lower lifetimes than solar.
- Consistent Performance: Can heat the pool in a wide range of weather conditions, unlike solar heaters.
- Generates in Winter: Solar PV produces energy in winter unlike a poly solar system.
- Good Payback Times: In some warmer Australian regions, a PV
solar + heat pump hybrid system is more financially advantageous than
poly solar after 15 years, especially if you can't DIY, but this
depends on what you prioritize; pool usage or electrical generation
(and faster payback).
- Very High Initial Cost: PV systems are however subsidized
somewhat.
- Noise: Heat pumps can generate noise.
- Lower lifespan: Heat pumps have lower lifetimes than poly solar.
When choosing a swimming pool heating system, it's critical to understand what pool temperatures you'll get with different systems and whether or not this will suit your requirements and lifestyle. For example, solar is not an on-demand type system, so there may be times the pool is slightly under-temperature, but while active kids might tolerate cooler pool temperatures, older folks will appreciate a warmer pool.
Proper system sizing is also a fundamental factor when choosing a pool heating system. A solar pool heater, for example, could be ruled out due to insufficient roof space availability; a heat pump could be undersized and run excessively, never coming up to temperature in the shoulder season. The size of your pool heating system also has a small impact on the system's running cost. We've developed a pool water temperature simulation calculator which will tell you the water temperatures you can expect for differently sized systems.
Q. What is the best heating option
for a pool?
A. The best option for a swimming
pool heating system depends on your specific needs, budget, location,
and pool temperature requirements. For long-term, low-cost operation,
solar pool heating systems are an excellent choice if you have the
available roof space. For a more "on demand" heating requirement, when a
pool absolutely must be heated at a specific time, utility heating will
be required. A pool heat pump is the more efficient option as compared
to a gas heater; however, a gas heater will heat a pool faster if time
is of the essence.
Q. What is the best way to heat a
swimming pool?
A. The most efficient and
effective way to heat a swimming pool is by combining a pool heating
system with heat retention strategies like a pool cover and/or removal
of shading and/or extra wind sheltering for a pool. A quality cover can
prevent up to 70% of heat loss, primarily from evaporation, which is the
leading cause of heat loss for outdoor pools overnight. This
significantly reduces the workload on your heating system, regardless of
the type of swimming pool heating system you choose.
Q. What are the different types of
pool heating systems?
A. There are three main types of
pool heating systems (worth considering): solar based, which use
the sun's energy; heat pumps, which transfer heat from the air;
gas/propane heaters, which burn fuel to generate heat; and
electric resistance heaters, which convert electricity into heat. Each
has unique advantages in terms of cost, efficiency, and heating speed.
Q. What's the cheapest way to heat my
pool?
A. The cheapest way to heat a
pool in terms of operating costs is with a solar pool heating system by
far. Once the initial installation cost is covered, operating costs are
minimal. A pool heat pump is the next most cost-effective option for
operating costs, as it's far more efficient than gas heaters but nowhere
near as efficient as solar. For a minimal-cost, non-mechanical solution,
a transparent solar pool cover, combined with clever wind sheltering
strategies, are the most cost-effective way to retain heat.
Q. What is the most efficient way to
heat a pool?
A. The most efficient and
effective method to heat a pool by far is solar with COP factors
approaching 50 to 100. Heat pumps are next with a COP factor of 5 to 7.
The least efficient are gas heaters and electric element heaters, which
are very expensive to run.
Q. Do swimming pool heaters really
work?
A. Yes, absolutely pool heaters
work. They are specifically designed to add thermal energy to the pool
water, raising its temperature to a comfortable level. A correctly sized
and properly installed pool heating system can significantly extend your
swimming season and make your pool usable on cooler days. The
effectiveness of any pool heating system is greatly enhanced by using a
pool cover to reduce heat loss. Having said that, there are times in the
off-season where almost no amount of heating can offset overnight
cooling; here, only gas heating has the potential to maintain pool
temperatures for a short period before needing to be switched off due to
running costs.
Q. Can you add a pool heater to an
existing inground pool?
A. Yes, you can easily add a pool
heating system to an existing inground pool; however, the level of
difficulty depends on the facilities your pool manufacturer included in
your pool. For example, solar needs suction and return ports. Having
said that, even if these are not present, installations can still
proceed by plumbing the heater into the existing filtration and
circulation system.
Q. How much heat will a pool lose
overnight?
A. A pool can lose a significant
amount of heat overnight, primarily through evaporation. The amount of
heat lost depends on the pool's surface area, air temperature, wind
speed, and humidity. A pool without a cover can lose a few degrees
Celsius in a single night.
Q. How to warm a pool with no heater?
A. To warm a pool without a
dedicated heater, you can use passive methods. A transparent solar pool
cover is the most effective. It both traps existing heat and allows
solar radiation to pass through to warm the water. Other methods involve
reducing the wind exposure of a pool. Running the pool's filter pump in
the afternoon can also help mix the stratification layer that develops
in the top layers of a pool. Without this mixing, the pool cools
excessively overnight.
Q. Are heat pumps for pools worth it?
A. This really depends on the
heat loading requirements. Some people who don't use energy-saving
measures like a pool cover will quickly find that running a heat pump is
very expensive and may choose to forgo pool usage as a result. However,
with proper use of a cover, a heat pump can provide consistent, reliable
heating.
Q. What is a comfortable pool
temperature?
A. A comfortable pool temperature
for most people is generally between 26°C and 29°C. For serious athletic
swimming, a cooler temperature of around 24°C is often preferred. For
leisurely use, hydrotherapy, or for young children, temperatures at the
higher end of the range, closer to 30°C, are common. Choosing a pool
heating system allows you to maintain this ideal temperature.
Q. Can I leave my pool heater on all
the time?
A. You can certainly, and you
should leave a solar pool heating system running continuously. This is
because the ground around the pool takes time to warm up and hence the
highest possible pool temperature is only achieved with continuous
heating. Regarding utility heating, a heat pump can be left on if the
pool is covered with a solar blanket. An uncovered pool heated using
either a heat pump or gas heater will be very expensive to heat
continuously or for any extended season length, but these units may be
left on during the warm summer months to "top up" the pool. It is a myth
that turning these heaters ON/OFF will somehow lead to electrical
efficiency and result in higher electricity usage for less heat output.
Q. What are the disadvantages of a
pool heat pump?
A. The main disadvantages of pool
heat pumps are their relatively slow speed to bring a pool up to
temperature and some can be noisy in the backyard. Keep in mind they
literally pull heat from the air so they can cool an enclosed backyard
if the air is not expelled properly. They are also not that effective in
very cold weather, as their efficiency drops significantly. The initial
purchase and installation cost is typically higher than for other
swimming pool heating systems.
Q. Should I run my pool during the
day or at night?
A. You should run your pool pump
and any pool heating systems during the day. This is particularly true
for solar pool heating systems which require sunlight to operate. Heat
pumps are also most efficient during the day when the air temperature is
warmer. Running the filter pump during the afternoon is also helpful to
mix the stratification layer that develops during the day to prevent
surface cooling at night.
Q. What is the life expectancy of a
pool heat pump?
A. The typical life expectancy of
a pool heat pump is between 10 and 15 years. The actual lifespan depends
on the quality of the unit, how often it's used, the local climate, and
the regularity of maintenance. Using a quality pool heating system and
performing routine care can help ensure a long service life.
Q. Which pool heater lasts the
longest?
A. A quality solar pool heating
system will generally have the longest lifespan. The collectors
themselves are often made of durable materials such as HDPE and can last
up to 30 years if not more. The other components are simple and easy to
replace. Pool heat pumps are next, with a typical lifespan of 10-15
years, while gas heaters generally last for 5-10 years due to the
corrosive nature of the combustion process on their heat exchangers.
Q. How much does it cost to heat a
swimming pool?
A. The cost of heating a swimming
pool varies widely and depends on several factors, including the type of
pool heating system you use, the cost of energy in your area
(electricity, gas), the desired temperature, the pool's size, how well
the pool is insulated with a cover, and other heat loading factors. Gas
heaters are typically the most expensive to operate on a daily basis,
while solar pool heating systems have the lowest operating cost.