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.
