Heat Pump Pool Heater Myths, Tested Against Physics

Pool heating attracts more confident misinformation than most household equipment, partly because the technology is genuinely counterintuitive and partly because there are four competing products and everyone is selling one of them.

Here are the claims that come up most often about a heat pump pool heater, and what is actually true.

"It cannot produce more energy than it uses"

Correct, and it does not.

This is the objection that sounds like a physics violation, and the scepticism is reasonable until you understand what the machine does.

A heat pump does not generate heat. It moves heat that already exists in the surrounding air into your pool water. The electricity you buy does not become the heat, it powers the fan and compressor that relocate it.

So a unit delivering four or five times more heat energy than the electricity it consumes is not creating energy. It is collecting diffuse, low grade warmth from a large volume of air, concentrating it, and depositing it in your pool.

No conservation law is troubled. It is a removals business, not a manufacturing one.

"They do not work in cold weather"

Partly true, and the way it is usually stated is misleading.

Output falls as ambient air temperature falls, because there is less available heat to collect. That much is correct and it is the fundamental trade off against gas.

What is not correct is the implication that they stop working in Australian conditions. Every unit has a minimum operating temperature, and in most of populated Australia that threshold is well below what winter delivers.

The real issue is specification. A unit sized against summer conditions will disappoint in July. A unit sized against genuinely cool ambient conditions, paired with a cover, will hold temperature.

The honest version: they work in cold weather at reduced output, and whether that is enough depends entirely on whether anyone accounted for it at sizing.

"They are slow, so they are not really practical"

True on the first half, misleading on the second.

A heat pump is slow from cold. A pool is an enormous mass of water and moving heat into it gradually takes time. If your requirement is a warm pool by Saturday having decided on Friday, this is the wrong technology and gas is genuinely better.

But that is not how most people use a pool. Most households want the water to be reliably right when they feel like swimming, which means holding a temperature rather than sprinting to one. Heat pumps are extremely good at holding.

The honest version: slow to arrive, cheap to stay. Match that to your actual pattern rather than your imagined one.

"Inverter means it is efficient"

Not necessarily, and this is the claim most worth interrogating.

The word covers at least three technologies:

On off units have one speed, maximum. They overshoot the setpoint, stop, drift down, and restart.

Stepped inverters have a handful of fixed speeds and cycle between them.

Full inverters vary compressor speed continuously across the range.

The reason it matters is counterintuitive: heat pumps are most efficient running slowly. At reduced compressor speed the refrigerant spends longer in contact with the heat exchangers, so you extract more heat per unit of electricity at part load than at full output.

Since holding a pool at temperature is a low demand job most of the time, a unit that can sit at low output spends most of its life in its efficient band. One that only has full power cannot.

The honest version: ask whether compressor speed is continuously variable or stepped. See the Evo Force-i Pro.

"A bigger unit will heat it faster and better"

Half true and it leads people astray.

A larger unit does have more output. It also costs more, and with on off technology an oversized unit short cycles, starting and stopping repeatedly, which is inefficient and hard on a compressor.

More importantly, oversizing does not fix the actual problem in most disappointing installations, which is heat loss rather than heat input. A pool losing heat rapidly overnight because it is uncovered will not be rescued by a bigger machine.

The honest version: correct sizing beats maximum sizing, and a cover beats both.

"The running cost figures are marketing"

Sometimes, and the way to tell is specific.

Efficiency figures are real but enormously condition dependent. A peak coefficient of performance is measured at the machine's single most favourable operating point, which bears little relationship to a cool April morning.

The tell is whether conditions are stated. A single number with no conditions is not useful. A performance curve across a range of ambient temperatures is.

The honest version: the technology genuinely multiplies energy. The specific number quoted may be measured somewhere you will never operate.

"You have to switch it off to save money"

Backwards, and it is the most common operating error.

A pool is a large thermal mass. Reheating from cold takes substantial energy. Holding a temperature costs comparatively little because you are only replacing ongoing losses.

Households that switch off between swims and reheat repeatedly spend more than households that set a temperature and leave it.

The honest version: hold the setpoint. Drop it for extended absences rather than switching off entirely.

"They are noisy"

There is a fan and a compressor, so there is sound. Whether it is a problem depends on placement and technology.

A full inverter running gently at part load is considerably quieter than a fixed speed unit that is either at full noise or silent. Positioning matters more than the decibel figure: under a bedroom window is a decision you will revisit regardless of the unit.

The honest version: not silent, generally unobtrusive when correctly placed, and quieter at part load.

Frequently asked questions

Can a heat pump cool my pool?

Reversible models can, which in tropical and subtropical Australia is a genuine feature rather than a novelty.

Do they work at night?

Yes. Unlike solar they depend on ambient air temperature, not sunlight, which is one of their main advantages.

How long do they last?

Long term equipment given clear airflow and balanced water chemistry. Units that run steadily at part load cycle less, which reduces mechanical wear.

Are they better than gas?

Different. Gas wins on speed and weather independence. Heat pumps win decisively on cost per hour of swimming across a long season.

What is the single biggest factor in whether I am happy with one?

Correct sizing, followed by using a cover.

Judge it on your own pattern

Most disagreement about heat pumps comes from people comparing them against a use case they were never designed for.

Browse the full pool heater range, or request a free personalised pool heat report.

Installing a Heat Pump for Swimming Pools: What Happens on the Day

Most people research the product thoroughly and arrive at installation day with no idea what is about to happen in their backyard.

That gap causes avoidable friction: a unit ends up somewhere nobody is happy with, a cost appears that nobody budgeted, or the pool is out of action longer than expected.

Here is what installing a heat pump for swimming pools actually involves, in order, and the decisions you should make before anyone arrives.

Before the day: the site visit

Any competent installer will look at the site before quoting. If yours has quoted from a phone call, that is worth questioning.

What they should be assessing:

Where the unit can go, with manufacturer clearances on all sides and above for airflow.

The distance to the existing plant, since pipe runs affect heat loss and pump load.

Your electrical supply, both what the property has and whether the switchboard has capacity and space.

Your existing circulation pump, and whether its actual flow rate at the speed you run it suits the heater's requirement.

Access, for getting the unit into the yard. These are not light and they do not go through a standard gate on a trolley in every case.

Drainage, because the unit produces condensate.

The placement decision, which is yours to weigh in on

This gets decided quickly on the day if you have not thought about it, and you live with it for years.

Airflow is non negotiable. The unit extracts heat from air. Clearances exist for a reason and a boxed in unit works harder for less.

Noise. There is a fan and a compressor running for extended periods, often early morning. Walk the boundary before you decide. Under your bedroom window is bad. Under a neighbour's bedroom window is worse and harder to undo.

Exhaust direction. The discharged air is cooler than ambient. Do not point it at your outdoor seating.

Sight lines. You will look at this from the house for years.

Service access. Someone will need to reach it in five years. Do not plan a garden bed around it.

Sun exposure. Not critical, though a unit in permanent full afternoon sun works marginally harder.

The best outcome comes from walking the yard with the installer and agreeing the position deliberately rather than accepting the first practical spot.

The electrical work

This is where unbudgeted cost most often appears.

Supply type. Larger units may require three phase. Many Australian homes are single phase, and an upgrade is a substantial separate cost involving your network distributor.

Switchboard capacity and space. Older boards may need work regardless of supply type.

A dedicated circuit. Standard for this kind of load.

Cable run. From the board to the unit, and distance affects cost.

All of this must be done by a licensed electrician. Get it priced as part of the project rather than discovered on the day, and ask specifically whether any switchboard or supply upgrade is included or excluded.

The plumbing

Generally more straightforward than the electrical work.

The heater goes into the circulation loop, normally after the filter so it receives clean water.

A bypass is usually fitted so the heater can be isolated for service without shutting down circulation.

Non return valves where required.

Union fittings so the unit can be disconnected without cutting pipe.

Flow rate check, confirming your pump delivers what the heater needs at the speed you actually run it. Variable speed pumps set to a low eco speed are a common and easily missed problem.

Commissioning, and what to insist on

The part most often rushed, and the part that determines whether you understand your own equipment.

Ask your installer to:

Run it and confirm it is heating, with water temperature rising.

Show you the controller. How to set a temperature, how to set a timer, how to read the display.

Set up the app, if the unit has one. Do this while they are there, not from a manual afterwards.

Explain the operating logic. Specifically that you set a temperature and leave it, rather than switching on and off.

Tell you realistic heat up time for your pool from its current temperature.

Hand over documentation. Manual, warranty, model and serial number, installer details.

Explain what voids the warranty, particularly regarding water chemistry and airflow obstruction.

If commissioning takes four minutes and ends with "it's all set", ask for the walkthrough.

The first fortnight

Do not panic. A pool is an enormous mass of water. Heating from cold takes days on a heat pump, not hours. New owners frequently check three hours in and conclude something is wrong.

Set your temperature and leave it running. Resist the urge to switch it off overnight.

Put the cover on. Every night. This is when you establish the habit that determines your running cost.

Watch for anything unusual. Odd noise, water pooling beyond normal condensate, error codes. Report early.

Do not landscape around it yet. Live with the position for a season before you build a screen.

What is usually not included

Worth asking about explicitly rather than assuming:

• Electrical supply or switchboard upgrades

• A concrete pad or base, if required

• Pool cover and roller

• Removal and disposal of an old unit

• Any council or body corporate approvals

• Landscaping or screening

Frequently asked questions

How long does installation take?

Typically a day for a straightforward installation. Electrical supply upgrades add time and are usually a separate visit.

Can I use the pool during installation?

Circulation is interrupted while plumbing is connected. Ask for the specifics on the day.

Do I need council approval?

Usually not for the heater itself, though noise provisions may apply and bodies corporate frequently have requirements. Check before installation.

Can I install it myself?

Electrical and plumbing connections require licensed trades, and placement materially affects performance. This is not a good DIY candidate.

What if I do not like where it ended up?

Moving it later means new electrical and plumbing work. Agree the position before it is fixed.

How soon can I swim?

As soon as it is commissioned, though the water will take days to reach temperature from cold.

Walk the yard before you sign

Placement, electrical supply and commissioning are the three things that determine whether you are happy, and all three are decided before or during installation day.

Browse the full pool heater range, or request a free personalised pool heat report.

The Ideal Pool Temperature in Australia, and What Each Degree Costs You

There is no single correct pool temperature, which is inconvenient because it is the question everyone asks first.

What there is instead is a comfortable range that shifts depending on who is swimming and what they are doing in there, and a running cost consequence that grows disproportionately the higher you push it.

Understanding both is how you land on your own ideal pool temperature rather than someone else's.

Why there is no single answer

Water conducts heat away from a body far faster than air does. That is why still water at a temperature you would find pleasant as air feels cold, and why a small change in water temperature produces a large change in perceived comfort.

But how much heat your body is generating changes the equation entirely.

A lap swimmer working hard generates a lot of heat and needs the water to carry it away. Water that a child finds pleasant will feel oppressive to them after ten laps.

A child playing moves in bursts and spends time standing still. They cool quickly and have a higher surface area relative to body mass, so they feel cold sooner than adults in the same water.

Someone doing gentle exercise or therapy generates very little heat and is often in the water for extended periods, so they need it warmer again.

An adult lounging sits between the two.

So the same pool serving a family with young children, a parent doing laps at 6am, and a grandparent doing gentle movement is genuinely being asked to be three different temperatures.

The general comfort bands

These are commonly used guides rather than rules, and personal preference varies considerably.

Competitive and lap swimming sits at the cooler end. Serious swimmers frequently find water that feels pleasant to a casual bather uncomfortably warm once they are working.

General family swimming and recreation sits in the middle, and this is where most domestic pools are set. Comfortable to get into without a gasp, comfortable to stay in.

Young children, gentle exercise and therapeutic use sits at the warmer end. Less heat generated, longer time in the water, more warmth required.

Spas are a different category entirely, considerably warmer than any of the above, because you are sitting still. See spa heating.

The practical approach: pick a setpoint, live with it for a fortnight, and adjust by a single degree at a time. Everyone in the household will have an opinion, and the compromise is usually a degree below what the coldest family member wants.

Why each degree costs more than the last

This is the part that changes how people set their pool, and it is worth understanding properly.

Heat loss from a pool is driven by the difference between the water temperature and the surrounding environment. The bigger that gap, the faster the pool loses heat.

So when you raise your setpoint by a degree, two things happen at once. You have to add energy to get there, which is a one off. And then you have to keep replacing losses that are now permanently higher, every hour, for as long as you hold that setting.

The consequence: the cost of a degree is not linear. Going from a moderate setting to one degree warmer costs more than the previous degree did, and the one after costs more again. Pushing well above comfortable is where pool running costs get genuinely alarming.

The corollary is the useful bit. Dropping your setpoint by a single degree, if nobody in the household actually notices, is one of the most effective running cost reductions available to you. It costs nothing to try.

The cover changes this more than the thermostat

Before adjusting your setpoint, deal with evaporation.

Evaporation is the largest single heat loss mechanism in an outdoor pool, by a wide margin, and it peaks overnight when the air cools and the water does not. An uncovered pool spends every night giving your heating back to the sky.

A cover reduces that loss dramatically. In practical terms, a covered pool holds a higher temperature for the same energy input, which means you can either run warmer for the same cost or the same temperature for less.

If you are unhappy with either your temperature or your bill, the cover is the first thing to address, ahead of the thermostat and well ahead of the heater.

Seasonal strategy, rather than one setting

Most people set a temperature once and leave it. There is a better approach.

Peak summer. You may need no heating at all in warmer parts of Australia, and in the tropics the question can invert entirely into whether you need cooling. Reversible heat pumps can pull heat out of a pool that has become uncomfortably warm.

Shoulder seasons. This is where heating earns its keep, and where a sensible setpoint turns a three month pool into a nine month one.

Winter. If you are swimming through it, expect to hold a setting continuously and expect the cost to be highest here, because the gap between water and air is widest.

Extended absences. Drop the setpoint rather than switching off entirely. Reheating a fully cold pool on a heat pump takes a long time, so maintaining a lower baseline is usually both cheaper and more convenient than starting from cold. App and timer control makes this easy on modern units.

Regional differences across Australia

Your postcode changes what a given setpoint costs you, even for identical pools.

Tropical north. Long natural season, warm nights, minimal gap between water and air. Holding a temperature here is comparatively cheap, and cooling may be the more relevant capability.

South east Queensland and northern New South Wales. Comfortable through summer, cool either side. Shoulder season heating is where the value sits.

Sydney and coastal New South Wales. Bigger day to night swing, so overnight losses matter more and the cover becomes disproportionately valuable.

Melbourne, Adelaide and the temperate south. Cool nights well into the warmer months and genuine winter. Holding any setpoint costs more here because the gap is larger for more of the year.

Perth. Warm days, but the afternoon sea breeze strips heat off an open surface efficiently. Shelter and cover matter more than the raw temperature figures suggest.

Tasmania, ACT and the highlands. The most demanding conditions in the country. Year round swimming is achievable but has to be designed for from the outset.

There is a fuller breakdown in the complete pool heater guide.

Measuring it accurately

Worth a mention, because a surprising number of temperature complaints are measurement problems.

Your heater's display reads at the plant, not in the pool. Depending on pipe runs and whether the pump is running, those can differ.

Surface water is warmer than water at depth, especially on a sunny day in an unmixed pool. A thermometer floating on top will read high.

Cheap thermometers drift. If you are making decisions based on single degrees, it is worth having something you trust.

Check at the same time of day. Early morning, before solar gain, is the most honest reading and the one that tells you whether your heater is holding overnight.

Frequently asked questions

What temperature should I set my pool to?

Somewhere in the general recreational comfort band, adjusted for who actually swims. Start in the middle, live with it for a fortnight, and adjust one degree at a time.

Is a warmer pool less healthy?

Warmer water is chemically more active, so sanitiser is consumed faster and water balance needs closer attention. That is a maintenance consideration rather than a health one, but it does mean heating and water care go together.

Why does my pool feel colder than the display says?

Possibly a measurement issue, possibly stratification, possibly wind chill as you get out. Check with a trusted thermometer at depth, early in the morning.

How much does one degree cost?

It depends on your pool volume, climate, cover use, exposure and tariff, and it costs more for each additional degree. Anyone quoting a firm figure without those inputs is guessing. What is reliable is the direction: each degree costs more than the last.

Should I turn it off when we go away?

Drop the setpoint rather than switching off. Reheating from fully cold takes a long time on a heat pump.

Do children need it warmer?

Generally yes. They generate less heat, cool faster, and will simply refuse to use a pool they find unpleasant, which defeats the purpose of having one.

Can a pool be too warm?

Yes. In tropical Australia pools can become uncomfortably warm at the peak of summer, which is why reversible units that can cool are a genuine feature rather than a novelty.

Work out your number properly

The right setpoint depends on your household, and what it costs depends on your pool, your climate and your cover.

Request a free personalised pool heat report, read the complete pool heater guide, or browse the pool heater range.

Types of Pool Heaters Compared: Which One Suits Your Pool

Most comparisons of pool heaters are written to sell one particular technology, which is why they all reach a confident conclusion and none of them agree.

This one is organised differently. Rather than declaring a winner, it sets out what each type is genuinely best at, then gives you a way to match that against how you actually use your pool. There is no universally correct answer, only a correct answer for a specific backyard.

The four technologies at a glance

| Type | Speed from cold | Running cost | Works at night | Weather dependent | Best suited to |

| Gas | Fastest | Highest per hour | Yes | No | Occasional, on demand use |

| Electric element | Fast | Highest per unit of heat | Yes | No | Very small volumes, spas |

| Solar | Slow | Lowest | No | Completely | Summer extension, suitable roof |

| Heat pump | Slow to moderate | Low | Yes | Partially | Regular use, long season |

The table is a starting point. The detail underneath it is where the decision actually gets made.

Gas heating in detail

How it works. Natural gas or LPG burns in a combustion chamber and transfers heat directly to water flowing past a heat exchanger.

Its genuine strength. Speed, and independence from weather. A gas heater does not care whether it is a clear night or an overcast July afternoon. It produces its rated output on demand, every time.

Its genuine weakness. Every hour of operation consumes fuel, and there is no efficiency multiplier available. Heat delivered is a direct function of gas burnt.

Cost structure. Moderate to buy, moderate to install if you already have gas connected, expensive to run continuously.

Practical notes.

• Requires a gas connection with adequate supply. LPG means bottle management and delivery.

• Combustion means flue and clearance requirements. Placement is more constrained than people expect.

• Nothing beats it for a spa taken from cold to hot in under an hour.

• Gas pricing in Australia has moved unfavourably, which has changed this calculation considerably over the past decade.

The honest scenario where gas wins: a holiday house used six weekends a year, where you arrive Friday evening and want a warm pool Saturday morning, and the total annual run time is low.

Electric resistance heating in detail

How it works. An electric element in the water flow converts electricity to heat, exactly like a kettle element.

Its genuine strength. Simplicity, low purchase price, and no dependence on ambient conditions.

Its genuine weakness. Physics. It converts electricity to heat at one to one, which makes it the most expensive way to deliver a unit of heat in Australia.

Cost structure. Cheapest to buy, most expensive to run.

Practical notes.

• Perfectly sensible for a spa, a plunge pool, or anything small with short run times.

• Occasionally used as a backup or booster alongside solar.

• For a full sized pool it is very rarely the right answer, and anyone recommending one for a family pool should be asked why.

Solar heating in detail

How it works. Pool water is pumped through collectors on a roof. Sun warms the water, which returns to the pool. A controller diverts flow when the collectors are warmer than the pool.

Its genuine strength. Running cost. Once installed you pay for a little extra pump time and nothing else. Nothing comes close.

Its genuine weakness. Control. Solar delivers heat when conditions allow, not when you want it. No sun means no heat.

Cost structure. Moderate to high install, near zero running cost, long payback that is genuinely attractive if you have the roof for it.

Practical notes.

• Needs real roof area with suitable orientation. North facing is ideal in Australia. Shading from trees or neighbouring buildings undermines it.

• Two broad types: unglazed rubber or polymer matting, cheaper and lower output, and glazed panels, dearer and better in cooler conditions.

• Collector area is roughly proportional to pool surface area. Undersized collector area is the most common installation failure.

• Adds pump running hours, which is a small but real cost.

• Effectively zero output overnight or through a wet week.

The honest scenario where solar wins: a household with good roof aspect who want to stretch summer from three months to five or six, and who accept the water being whatever the weather delivers.

Heat pump heating in detail

How it works. A fan draws ambient air across an evaporator containing refrigerant chosen to boil at low temperature. The refrigerant absorbs heat and becomes gas. A compressor concentrates that heat into a small volume of hot gas. A heat exchanger transfers it into the pool water. The refrigerant cools, condenses, and the cycle repeats.

Crucially, it is not generating heat. It is collecting low grade heat that already exists in the air, concentrating it, and delivering it to your pool. That is why output substantially exceeds electrical input.

Its genuine strength. Cost per hour of usable swimming, combined with genuine control. It works overnight, under cloud, and through cooler months.

Its genuine weakness. Slower from cold than gas, and output falls as ambient air temperature drops.

Cost structure. Higher to buy than solar or electric, low to run, and the running cost advantage compounds over a long season.

Practical notes, and the one that matters most.

Not every unit sold as an inverter is a full inverter. There are three control types:

• On off (fixed speed). One speed, maximum. Overshoots, switches off, drifts down, fires up again.

• Stepped inverter. A handful of fixed speeds. Better, but still cycling between fixed points.

• Full inverter. Continuously variable compressor speed across the whole range.

This matters because heat pumps are most efficient running slowly, and holding a pool at temperature is a low demand job most of the time. A unit that can throttle down and sit there gently spends most of the season in its efficient band. One that cannot, does not.

Ask directly whether compressor speed is continuously variable or stepped. See the Evo Force-i Pro for a genuine full inverter.

The honest scenario where a heat pump wins: the great majority of Australian family pools, used regularly across an extended season, where the owner wants the water reliably at a set temperature without dreading the bill.

Matching technology to how you actually swim

"We swim most days from September to May."

Heat pump. This is exactly what the technology is designed for.

"We use the pool maybe eight times a year, unpredictably."

Gas. You are paying for readiness rather than efficiency, and your total run hours are low.

"We want to stretch summer and we have a big north facing roof."

Solar, possibly with a heat pump later for the shoulders.

"We want to swim through winter in Melbourne."

Heat pump, sized against genuinely cool ambient conditions, with a cover. Do not let anyone size this off summer.

"It is a small plunge pool."

Heat pump for regular use, electric element if it is occasional and small.

"It is a spa."

Different problem entirely. See spa heating.

"It is a commercial or public pool."

Different sizing discipline and different duty expectations. See commercial pool heaters.

The factor that beats all four

Whichever technology you install, a pool cover will do more for your running cost than the choice between them.

Evaporation is the dominant heat loss mechanism in any outdoor pool. It happens hardest overnight, when the air cools and the water does not. An uncovered pool loses a large share of the heat you paid for, every single night, regardless of what produced it.

A cover reduces that loss dramatically, cuts water and chemical consumption, and can allow a smaller heater to achieve the same result. It is the cheapest efficiency upgrade in pool ownership and the most commonly deferred.

Frequently asked questions

Can I combine two types?

Yes, and it is common. Solar plus heat pump is the most sensible pairing, with solar carrying the warmer months and the heat pump covering shoulders and winter. It needs proper control integration so the two do not fight each other.

Which type has the lowest total cost of ownership?

For regular use over a long season, a correctly sized heat pump generally wins, because the running cost advantage compounds. For genuinely occasional use, gas can win despite the higher hourly cost, simply because you run it so few hours.

Does gas heat a pool faster than a heat pump?

Yes, from cold. That is gas's principal advantage. Whether it matters depends entirely on whether you heat from cold or maintain a temperature.

Is solar enough on its own?

For summer extension with suitable roof aspect, often yes. For control over temperature, or for winter, no.

How do I compare quotes across different technologies?

Ask each supplier for output at the ambient conditions during the months you intend to swim, not headline output. Then ask what the running cost assumption is and what it is based on. Quotes that do not state their assumptions cannot be compared.

What size do I need?

Volume alone will not answer it. Target temperature, climate, cover use and exposure all matter. See specifying a pool heat pump, or request a free personalised pool heat report.

Next steps

Work out how you swim before you compare products. The technology follows from the habit.

Read the complete pool heater guide, browse the full range, or request a free personalised pool heat report.