Pool Heat Pump Size Chart by Pool Volume
The chart everyone asks for, with the two things that move it more than litres do.
A pool heat pump size chart matches your pool volume in litres to the kW output you need, and for a typical 40,000 litre pool that lands at about 12kW in Brisbane, 19kW in Sydney and 27kW in Melbourne if the pool is left uncovered. Put a cover on it and the Sydney figure drops to about 11kW. Same pool. Same water. Nearly half the heat pump.
Want the number for your exact pool? Our pool heat pump sizing calculator takes your pool size, postcode, cover habits and swimming season, works out the kW, and shows the units in stock that fit.
Every figure on this page comes from that same calculator model, so the chart and the calculator will never argue with each other.
The pool heat pump size chart (uncovered pools)
This chart gives the heat pump output in kW for an uncovered in-ground pool held at 28°C from October to April. That is the season most people actually want: warm water from the start of spring through to Easter. Sizing is set by the coldest month you want to swim, which for that season is October.
| Pool volume | Brisbane | Sydney | Perth | Adelaide | Melbourne |
|---|---|---|---|---|---|
| 10,000L | 3kW | 5kW | 6kW | 6kW | 7kW |
| 20,000L | 6kW | 10kW | 12kW | 12kW | 14kW |
| 30,000L | 9kW | 14kW | 17kW | 18kW | 20kW |
| 40,000L | 12kW | 19kW | 23kW | 24kW | 27kW |
| 50,000L | 15kW | 24kW | 29kW | 30kW | 34kW |
| 60,000L | 18kW | 29kW | 35kW | 36kW | 41kW |
| 80,000L | 24kW | 38kW | 46kW | 48kW | 54kW |
Uncovered in-ground pool, 28°C target, October to April season, average wind, part sun. Figures from the Waternex sizing model, October 2026.
Look at the bottom right corner. An uncovered 80,000 litre pool in Melbourne wants 54kW. Nobody sells a single residential unit that big, and you would not want the power bill if they did. That corner of the chart is the case for a pool cover, not a case for a bigger heat pump.
The same chart with a pool cover
A pool cover cuts the heat pump size you need by roughly 40 to 45 percent in most Australian cities. Evaporation off an open surface is where most pool heat goes overnight, and a cover stops it. Here is the same chart with the cover on whenever nobody is swimming.
| Pool volume | Brisbane | Sydney | Perth | Adelaide | Melbourne |
|---|---|---|---|---|---|
| 10,000L | 3kW | 3kW | 3kW | 3kW | 4kW |
| 20,000L | 5kW | 5kW | 6kW | 7kW | 8kW |
| 30,000L | 8kW | 8kW | 10kW | 10kW | 11kW |
| 40,000L | 10kW | 11kW | 13kW | 13kW | 15kW |
| 50,000L | 13kW | 13kW | 16kW | 16kW | 19kW |
| 60,000L | 15kW | 16kW | 19kW | 20kW | 23kW |
| 80,000L | 20kW | 21kW | 25kW | 26kW | 30kW |
Covered when not in use, otherwise the same assumptions as the uncovered chart. October 2026.
Brisbane barely moves because the water is not losing much heat in the first place. Melbourne nearly halves. The colder your city, the more a cover is worth. We wrote a whole piece on whether you need a pool cover with a heat pump, and the short version is yes.
The kW per litre rule of thumb
The quick rule is about 0.5kW per 1,000 litres for an uncovered pool in Sydney, and about 0.27kW per 1,000 litres once the pool is covered. Other cities shift that number up or down.
| City | kW per 1,000L uncovered | kW per 1,000L covered |
|---|---|---|
| Brisbane | 0.30 | 0.25 |
| Sydney | 0.48 | 0.26 |
| Perth | 0.58 | 0.32 |
| Adelaide | 0.60 | 0.33 |
| Melbourne | 0.68 | 0.37 |
Multiply your litres in thousands by the figure for your city. A 35,000 litre uncovered pool in Perth: 35 times 0.58 is about 20kW. Treat 0.25kW per 1,000 litres as the floor anywhere. Below that, a heat pump takes so long to lift the water that you give up waiting.
How to work out your pool volume in litres
Pool volume in litres is length times width times average depth in metres, times 1,000. Average depth is the shallow end plus the deep end, divided by two.
A 9m by 4m pool running from 1.0m to 1.8m has an average depth of 1.4m. That is 9 times 4 times 1.4, which is 50.4 cubic metres, or about 50,000 litres. For a kidney or freeform pool, measure the longest length and the widest width and multiply the result by 0.8. Close enough for sizing.
Why litres is only half the answer
Surface area drives heat loss, not litres. Heat leaves a pool through the top: evaporation, wind and radiation to a cold night sky. Litres is a convenient stand in because most pools have similar proportions, but a shallow 40,000 litre pool loses more heat than a deep 40,000 litre pool, because it has more surface open to the air.
Three other things push the number around.
- Season. A 40,000 litre uncovered pool in Sydney needs about 11kW for summer only, 19kW for October to April, and 35kW to swim all year. Swim all year in an uncovered pool and the cover stops being optional.
- Target temperature. The same Sydney pool needs 15kW at 26°C, 19kW at 28°C and 23kW at 30°C. Every two degrees costs you roughly 4kW.
- Wind and shade. An exposed, shaded pool sits above the chart. A sheltered pool in full sun sits below it.
Which heat pumps fit each size band
Pick the band your chart number falls into, then round up, never down. The models below are the ones we stock in each band.
| Chart says you need | Models that fit | Price from |
|---|---|---|
| Up to 9kW | Fairland Aqua X Essential 7.5kW, Guardian Eco Pulse 9kW | $2,645 |
| 10 to 14kW | Fairland Aqua X Essential 13.8kW, SensaHeat ES 13kW | $3,182 |
| 15 to 21kW | Midea M Series 20kW, Guardian Platinum 20kW | $3,799 |
| 22 to 28kW | Guardian Eco Pulse 24kW, Fairland Aqua X Essential 28kW | $5,500 |
| 29 to 35kW | Fairland Aqua X Essential 34.5kW, Guardian Eco Pulse 35kW | $8,246 |
| Over 35kW | Cover the pool first, then size again. If it still reads over 35kW, ask us about two units. | Quote |
Prices current as of October 2026, AUD including GST. Cheapest unit in each band shown; see the full range in Heat Pumps for Pools & Spas.
The Midea 20kW is our best seller for a reason. On the chart above it covers an uncovered 40,000 litre pool in Sydney or a covered 60,000 litre pool in Perth, and it is the cheapest 20kW unit in the range.
What it costs to run at each size
A correctly sized heat pump on a 40,000 litre pool costs about $600 to $1,600 a season to run from October to April, depending on city and cover. These figures assume 33c per kWh.
| 40,000L pool | Uncovered | Covered |
|---|---|---|
| Brisbane | $629 | $346 |
| Sydney | $1,089 | $599 |
| Melbourne | $1,590 | $874 |
Full season running cost, 28°C target, October to April, 33c per kWh. October 2026.
The cover pays for itself in one to two seasons in most cities. More on the numbers in our guide to pool heat pump running costs.
Undersizing is the expensive mistake
An undersized heat pump costs more to own than the right size. It runs flat out every cold night, never quite reaches temperature, and wears its compressor out years early. A correctly sized inverter unit reaches temperature, then throttles back and sips power to hold it.
If your number lands between two sizes, buy the bigger one. The price gap between a 17kW and a 20kW unit is usually a few hundred dollars. The gap in how the pool feels on a cold October morning is not.
Frequently asked questions
What size heat pump do I need for a 50,000 litre pool in Australia?
A 50,000 litre uncovered pool needs about 24kW in Sydney, 15kW in Brisbane and 34kW in Melbourne for an October to April season at 28°C. With a pool cover, those drop to about 13kW, 13kW and 19kW.
How many kW per litre does a pool heat pump need?
A pool heat pump needs roughly 0.5kW per 1,000 litres for an uncovered pool in Sydney and about 0.27kW per 1,000 litres when covered. Brisbane sits lower at about 0.3kW uncovered and Melbourne higher at about 0.68kW uncovered.
What size heat pump do I need for a 30,000 litre pool?
A 30,000 litre uncovered pool needs about 14kW in Sydney, 9kW in Brisbane and 20kW in Melbourne. Covered, a 30,000 litre pool needs around 8kW to 11kW in most Australian cities.
Is it better to oversize a pool heat pump?
Going one size up from the chart is better than going one size down. A slightly oversized heat pump heats faster and then idles, while an undersized one runs flat out and still leaves the pool cool on cold nights.
Does pool depth change the heat pump size?
Pool depth changes the litres but not the heat loss much, because heat leaves through the surface. Two pools with the same surface area need a similar heat pump, even if one is deeper and holds more water.
Still not sure which size? Ask us
Send us your pool length, width, depth, postcode and whether you use a cover, and we will tell you the exact model that fits. If you would rather start from the beginning, our guide on what size pool heat pump you need walks through the reasoning behind this chart.
This chart is general information for Australian pool owners and is not a substitute for advice on your specific pool and site. 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.