The Cheapest Way to Heat a Pool (With Real Numbers)
What it actually costs to keep an Australian backyard pool warm, method by method, with the numbers instead of the sales pitch.
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The cheapest way to heat a pool is solar, because once the panels are on the roof the sun does the work for nothing. The catch is solar only heats when the sun is out, so it is slow and it drops off in winter. For warmth you can rely on any day of the year, the cheapest option is a pool heat pump. It costs roughly a fifth of what gas costs to deliver the same heat, and it beats an electric element hands down. Everything below is the working behind those two sentences.
The short answer, ranked by running cost
Ranked from cheapest to run to dearest, the order is solar, then heat pump, then gas, then electric element. That order almost never changes, whatever your pool size or postcode. What changes is how much the gap matters to you.
| Method | Running cost | The trade-off |
|---|---|---|
| Solar (roof collectors) | Close to nothing | Only heats in sun, slow, fades in winter |
| Heat pump | Low, works day or night | Higher purchase price than gas |
| Gas heater | High, three to four times a heat pump | Fast heat, brutal running cost |
| Electric element | Highest of the lot | Avoid for a full-size pool |
The real numbers: what it costs to add the same heat
Delivering one unit of heat into the water costs about 6 cents with a heat pump, about 20 cents with gas, and about 30 cents with an electric element. Solar is effectively free to run because the pump is already turning over. That is the whole argument in one line, and here is how it lands.
The figures below are per kilowatt hour of heat put into the pool, using electricity at 30 cents per kWh and gas at 5 cents per megajoule. Prices current as of July 2026, AUD.
| Method | Cost to add 1 kWh of heat | Why |
|---|---|---|
| Solar | About 0 cents | No fuel, just the existing pool pump |
| Heat pump (COP 5) | About 6 cents | Moves 5 units of heat per unit of power |
| Gas heater (90% efficient) | About 20 cents | Burns fuel, most of the heat lands in the water |
| Electric element (COP 1) | About 30 cents | One unit of power makes one unit of heat |
Read that column again. A heat pump costs roughly a third of what gas costs and a fifth of what an electric element costs, to put the exact same warmth in the pool. Over a season that difference runs into hundreds, sometimes thousands, of dollars.
Why a heat pump wins on running cost
A heat pump wins because it moves heat instead of making it. It pulls warmth out of the outside air and pumps it into the water, so for every unit of electricity it draws, a good one delivers five or more units of heat. That ratio is the COP, and it is the single number that separates a heat pump from every other powered option.
Gas and electric elements both make heat from scratch, so they can never beat a ratio of one to one. A heat pump quietly runs at five to one. That is not a small edge. It is the difference between a pool heating bill you notice and one you barely do.
Want the longer version of how the numbers stack up across every method? Our guide on how to heat a pool in Australia lays out each option in full.
Solar is cheapest to run, with one catch
Solar pool heating costs almost nothing to run because the only power it uses is the pump that pushes water up to the roof collectors and back. On a hot sunny day it works beautifully and free. The catch is right there in the sentence: it only works when the sun is out.
That means solar is slow to warm a cold pool, it does little on an overcast day, and it fades badly through winter exactly when you want heat most. Plenty of Australians run solar for the free summer warmth and add a heat pump to stretch the season either side. If you only ever swim in peak summer and you have the roof space, solar alone can be the cheapest answer full stop.
Gas is fast but the dearest way to keep a pool warm
Gas heating is the most expensive way to keep a pool warm, because a gas heater burns fuel every minute it runs and none of that fuel is free. It earns its place in one situation only: you want a cold pool hot in a hurry, once in a while, and you do not care what it costs for those few hours.
For a pool you keep warm all season, gas is a mistake on running cost. The heater that seemed cheap on the shelf hands you the bill every month after. This is the classic false economy in pool heating, and it is why gas keeps losing ground to heat pumps in Australian backyards.
The cheapest heat pump setup, in practice
The cheapest heat pump setup is a correctly sized inverter unit on a covered pool. Get those three things right and your running cost drops as low as a powered pool ever gets. Get them wrong and you throw away a chunk of the advantage you paid for.
Put a cover on the pool
A pool cover is the highest-value dollar you can spend on heating, full stop. An uncovered pool loses most of its heat overnight through evaporation off the surface, so the heat pump spends the next day replacing warmth that floated away. A cover traps it. Cover the pool and the same heat pump does far less work for the same result.
Choose an inverter model
An inverter heat pump costs less to run than a fixed-speed one because it throttles down to a low hum once the pool is warm, instead of slamming hard on and off. Our Guardian Platinum 20kW inverter and the Guardian Lux-V full DC inverter range are built for exactly this, holding temperature on a trickle of power.
Size it right, not small
Sizing the heat pump correctly saves more money than buying the cheapest one. An undersized unit runs flat out and never quite gets there, chewing power for a pool that still feels cool. A right-sized unit reaches temperature and idles, sipping electricity to hold it. If you are unsure what fits, our pool heat pump sizing guide walks you through it by litres, cover and climate.
What a heat pump costs to buy
A pool heat pump costs between about $2,690 and $12,000 to buy in our range, depending on size and how quiet and efficient you want it. That is the one place gas looks cheaper, on the sticker, and it is why some people still get talked into gas and regret it later. Prices current as of July 2026, AUD including GST.
At the small end, the Guardian Eco Pro 9kW sits around $2,690 for plunge pools and spas. The SensaHeat ES 13kW is about $3,200 for a small family pool. Our best seller, the Midea M Series 20kW with WiFi, is $3,799 and suits most standard family pools, which is why it is the unit people land on from our Midea 20kW guide. At the big end the Guardian Eco Pro 35kW is about $9,451 for the largest backyard pools.
Spread across the ten or so years a good heat pump lasts, the higher purchase price is paid back many times over in the running cost you never hand to a gas company. See the full line-up in Heat Pumps for Pools & Spas, or browse the complete Heat Pumps collection.
Frequently asked questions
What is the cheapest way to heat a pool in Australia?
The cheapest way to heat a pool in Australia is solar, because it uses free energy from the sun and costs almost nothing to run. The catch is solar only heats when the sun is out, so for warmth you can rely on any day, a heat pump is the cheapest option. A heat pump costs about a fifth of what gas costs to deliver the same heat.
Is a heat pump cheaper to run than gas?
Yes, a heat pump is far cheaper to run than gas, roughly three to four times cheaper for the same heat. A heat pump moves heat out of the air rather than burning fuel to make it, so it delivers about five units of heat for every unit of electricity, while gas can never beat a ratio of one to one.
How much does it cost to run a pool heat pump per hour?
A mid-size 20kW pool heat pump costs roughly $1 to $2 an hour to run at typical Australian electricity prices, and much less once the pool is at temperature and it is only holding the heat. A cover and an inverter model both push that figure lower again.
Is solar pool heating really free?
Solar pool heating is close to free to run, but not quite, because it still uses the pool pump to push water up to the roof collectors. There is no fuel cost on top of that. The real cost of solar is the upfront installation and the fact it only heats when the sun is shining.
Does a pool cover reduce heating costs?
Yes, a pool cover reduces heating costs more than any other single thing you can add. An uncovered pool loses most of its heat overnight through evaporation, so a cover traps that warmth and lets a heat pump do far less work for the same water temperature.
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This guide is general information for Australian pool owners and is not a substitute for advice on your specific pool and site. Running costs are estimates based on typical energy prices and vary with your pool, climate and tariff. Pool heat pumps are electrical appliances and must be connected by a licensed electrician. Confirm final sizing with us or your pool professional before you buy.