What it costs to heat a pool, and what each option can actually do
Pool heating is the one household energy decision where the cheapest option to run and the option that does the job are frequently not the same thing. Solar costs almost nothing and cannot hold a temperature. Gas costs the most and is the only thing that will warm a cold pool by Saturday. A heat pump sits in between and is usually the right answer, but not always.
So this page gives the running costs and then says, for each one, what you are actually buying.
The numbers first
| State or territory | Solar | Heat pump | Gas | Electric element |
|---|---|---|---|---|
| New South Wales | $120 | $1,103 | $2,112 | $6,069 |
| Victoria | $100 | $1,361 | $2,975 | $7,487 |
| Queensland | $102 | $649 | $1,322 | $3,568 |
| South Australia | $152 | $1,587 | $2,691 | $8,729 |
| Western Australia | $121 | $1,043 | $3,861 | $5,738 |
| Tasmania | $102 | $1,683 | no mains gas | $9,254 |
| Australian Capital Territory | $134 | $1,922 | $3,292 | $10,572 |
| Northern Territory | not needed | — | — | — |
A 48,000 litre pool held at 28 °C from September to April, with a bubble cover, at each state's reference rates. Solar is not the same product as the other three: its running cost is only the booster pump, and it cannot hold a temperature through a cold, cloudy week. Darwin appears as “not needed” because the air there averages 28.5 °C across those months and the water is already at swimming temperature.
Solar: nearly free, and not a heater
Solar pool heating pumps water through matting on your roof and back. There is no fuel, so the only running cost is the booster pump — around $100 to $150 a season in most of the country, which is why it looks unbeatable in a table of running costs.
What that table cannot show is the thing that decides whether it suits you: solar collects heat, it does not make it. It will add several degrees through the season and extend swimming by a month or two at each end. It will not hold 28 °C through a cold, cloudy week, and south of Brisbane it will not give you a warm pool in July at all. If what you want is a longer season it is the best value in pool heating by a wide margin. If what you want is a pool that is warm whenever you decide to swim, it is not the product.
Heat pump: the one that usually wins
A pool heat pump does the same thing as a reverse cycle air conditioner or a hot water heat pump — it moves heat out of the outside air rather than making it — and it does it unusually well, because the temperature lift is small. Warming water to 28 °C is a far easier job than heating air to 60 °C for a shower, and a pool heat pump manages a coefficient of performance around 5.5 as a result. Every unit of electricity moves about five and a half units of heat.
That is why it beats gas everywhere in the country, typically at a third to a half of the running cost. Its limitations are real but modest: it takes days rather than hours to bring a cold pool up, and its efficiency falls as the air gets colder — which is exactly when you are asking most of it.
Gas: expensive, and occasionally the right answer
A gas heater can never deliver more heat than it burns, so it starts at a disadvantage no amount of engineering closes. On the figures above it costs two to four times what a heat pump costs for the same heat.
It keeps one genuine advantage, and for some households it is decisive. Gas heats fast, from cold, on demand. A pool used a handful of weekends a year — a holiday house, a pool that is only wanted when visitors come — is better served by something that will take it from cold to swimming temperature in a day and then be switched off entirely than by something cheap to run that has to run continuously to be any use. Judge it on how you actually use the pool, not on the annual figure.
Electric element: included for completeness
An element heater buys one unit of heat for one unit of electricity, where a heat pump buys five and a half. It is the cheapest box to buy and the most expensive thing on this page to run, by a distance that is not close. It appears here because it is still sold, and because seeing the number is the fastest way to understand what a heat pump's coefficient of performance is actually worth.
The cover matters more than the choice
Whatever you heat with, most of the heat leaves through the surface and most of that goes as evaporation. Cover the surface and you stop it. This is the same pool, the same season and the same target temperature — the only difference is a sheet of bubble plastic:
| Heater | No cover | With a bubble cover | Saved |
|---|---|---|---|
| Heat pump | $3,678 | $1,103 | $2,575 |
| Gas heater | $7,041 | $2,112 | $4,928 |
| Electric element heater | $20,229 | $6,069 | $14,161 |
Same pool, same season, same target temperature in New South Wales — the only difference is a sheet of bubble plastic. The Australian Government puts the reduction in heat loss at up to 75%; this uses 70%, because a blanket only works on the nights it is actually on. Nothing else you can buy for a pool returns this much. Solar heating is not in the table because a cover does not change what it costs to run — it changes how warm the pool gets and how long the season lasts, which is a bigger effect and not one this table is in the right units to show.
The Australian Government also notes that a translucent bubble cover can warm an unheated pool by as much as 7 °C on its own, which for a lot of households is the entire heating decision made for a couple of hundred dollars.
How far to trust these figures
Further on the ranking than on the absolute numbers, and it is worth being explicit about why.
The ranking turns on efficiency ratios that are not in dispute: a burner cannot exceed 100%, an element is exactly 100%, and a heat pump moving heat at a small temperature lift is several hundred per cent. Those relationships hold whatever the weather does.
The absolute figures rest on a fitted heat loss coefficient rather than a measured one. Modelling pool heat loss properly needs humidity, wind and solar data for every capital, which this site does not carry, so the model uses surface area and the gap between your target temperature and the mean air temperature, with a coefficient set so that the results reproduce both the evaporation rates Australian pool suppliers report and the running costs the pool heating industry publishes. An exposed, windy site will do worse than these numbers and a sheltered one better.
This is the only model on the site fitted to industry figures rather than to a published determination, and the methodology page says so in the same words.
Frequently asked questions
What temperature should a swimming pool be?
Around 26 to 28 °C for general swimming, which is what the figures on this page use. Every degree costs real money — heat loss is proportional to the gap between the water and the air, so 30 °C costs substantially more than 28 °C, not marginally more. If you are heating at all, dropping the target a degree is the cheapest saving available after fitting a cover.
Can I use solar and a heat pump together?
Yes, and it is a common arrangement. Solar does the bulk of the work whenever there is sun, and the heat pump covers the cold snaps and the shoulders of the season. You pay for two systems, but you run the expensive one for a fraction of the hours. If you want both a long season and a reliable temperature, this is usually how it is done.
Does a pool heat pump work in winter?
It works, but less well and more expensively, because it has less heat in the air to move. Efficiency falls as the air temperature falls, so the season you can reasonably hold a temperature through is shorter the further south you are. In Hobart and Canberra, heating a pool through winter is possible and the figures above show what it would cost across an extended season; a full year would cost substantially more again.
Is it cheaper to leave pool heating on or turn it off between swims?
For a heat pump, leaving it on at a set temperature is usually cheaper than letting the pool cool and reheating it, because heat loss falls as the water cools towards ambient but the reheat has to put all of it back. For gas, the opposite is often true, because gas can reheat quickly enough to make on-demand use practical. A cover changes the sums for both, and in favour of leaving it on.