How long does it take to heat a pool in Adelaide?
Quick answer: A correctly sized heat pump takes two to four days to lift a covered 40,000 to 50,000 litre pool by around 10°C in spring. Solar gets there more gradually, over a run of sunny days. Gas is fastest (hours, not days) but the dearest to run. After the first heat-up, a heat pump or solar system just holds the temperature, which is far quicker and cheaper.
Spring's here, and one question comes up more than any other in September: "if I switch it on today, when can the kids swim?" Fair question. The honest answer depends on four things: how much water you've got, how many degrees you want to add, how big your heater is, and whether the pool has a cover on it.
Here's how to work it out for your own pool.
How much heat does a pool actually need?
Water takes a lot of energy to warm up. It takes about 1.16 kWh of heat to lift 1,000 litres by 1°C. So a 50,000 litre pool needs roughly 580 kWh of heat to rise 10°C.
A heat pump's rating (in kW) is how much heat it puts out per hour in good conditions. Divide the heat needed by the rating and you get the minimum number of running hours. Real pools lose heat while they warm, so the practical figure is always longer.
Heat-up time by pool size and heat pump size
The table below shows the pure heating hours for a 10°C rise, before any heat loss. On a covered pool in Adelaide spring weather, expect the real number to run roughly half as long again. Uncovered, it can be double or more, because the pool is shedding heat almost as fast as you add it.
Pool volume | Heat needed for +10°C | 13 kW heat pump | 17 kW heat pump | 24 kW heat pump |
30,000 L | about 350 kWh | about 27 hrs | about 21 hrs | about 15 hrs |
40,000 L | about 465 kWh | about 36 hrs | about 27 hrs | about 19 hrs |
50,000 L | about 580 kWh | about 45 hrs | about 34 hrs | about 24 hrs |
60,000 L | about 700 kWh | about 54 hrs | about 41 hrs | about 29 hrs |
Hours are continuous running at rated output. Heat pump output drops in cooler air, so a September heat-up takes longer than a December one.
Most family pools in Adelaide hold 40,000 to 60,000 litres and suit a 13 to 17 kW unit. Not sure of your volume? Our heat pump sizing calculator will work it out from your pool's dimensions and give you a starting size, and you can see prices for every Guardian model in our pool heat pump range.
What temperature should you heat your pool to?
Most families are happiest between 26°C and 28°C. Lap swimmers often prefer it a bit cooler, around 25°C to 27°C. Young kids, older swimmers and anyone using the pool for therapy usually want 28°C or more.
Every degree costs money to hold. So pick the lowest temperature your family is genuinely comfortable at, set it, and leave it. Chasing an extra two degrees for a weekend is where running costs creep up.
Solar, heat pump or gas: how fast is each?
They work differently, so "how long" means something different for each one.
System | First heat-up | Holding temperature | Running cost |
Gas heater | Fastest, usually hours | Works, but you pay for every degree | Highest |
Heat pump | 1 to 4 days, depending on size and weather | Set and forget, holds steady day and night | Low, 4 to 6 units of heat per unit of power |
Solar | Gradual, over several sunny days | Rises on sunny days, can dip in cloudy spells | Lowest, just your pool pump |
Solar plus heat pump | Solar does the bulk, heat pump tops up | Steady all season | Lower than a heat pump alone |
Solar pool heating doesn't heat on demand. It adds warmth whenever the sun's on your collectors, so you get a longer swimming season rather than a fast warm-up. If you're handy, our DIY solar pool heating kits are the same Zane Gulfstream collectors we install, sized from 18 square metres up. Two add-ons make solar noticeably quicker to respond: a Zane PC5 solar controller, which uses roof and filtration sensors to run the heating only when the roof is warmer than the pool, and a dedicated Waterco Supastream solar pump to push water up to the collectors. A pool heat pump is the set-and-forget option: pick a temperature and it holds it. If you're weighing the two, our solar vs heat pump comparison lays out running costs, season length and roof needs side by side.
Five ways to heat your pool faster
Put a cover on it. Evaporation is the biggest source of heat loss from an outdoor pool. A well-fitted cover can stop up to 97 percent of it and cut heating energy costs by 50 to 70 percent, according to this Australian council fact sheet on pool covers. It also shortens the heat-up dramatically.
Run the heat pump through the warmest part of the day. Heat pumps pull heat from the air, so they work harder and faster when it's 25°C out than when it's 12°C. If you've got solar PV on the house, daytime running uses your own power too.
Keep water flowing. Your pool pump has to run while the heater runs. A clogged skimmer basket or dirty filter cuts flow and slows everything down (we cover this in why your heat pump isn't heating properly). An old or undersized pump does the same.
Start early. Switching on in late September and letting the pool climb steadily is easier on the system than a hard push the week before a party.
Get the size right. An undersized unit will get there eventually, but in cooler weather it may never catch up with the heat you're losing overnight.
A worked example
Say you've got a 45,000 litre pool in the eastern suburbs, sitting at about 18°C in late September, and you want 27°C.
That's a 9°C rise, so roughly 470 kWh of heat. A 17 kW heat pump would need about 28 hours of pure heating. Add heat loss on a covered pool and you're looking at two, maybe three days of running. Leave it uncovered with cool nights and it could take a week, or stall a few degrees short.
Once it's there, the unit only has to replace what the pool loses each day. That's when a heat pump gets cheap to run.
What to do next
Measure your pool volume (length x width x average depth x 1,000 = litres).
Decide your target temperature and the months you want to swim.
Check your roof if you're considering solar. North, east or west-facing, largely unshaded, with area roughly equal to your pool's surface.
Talk to us. We've been heating Adelaide pools since 1979, and a quick onsite visit takes the guesswork out of sizing.
Ready to get your pool warm for summer?
Book a free onsite consultation anywhere in metro Adelaide, or call us on (08) 8349 4333. We'll measure up, look at your roof and your power, and quote fixed-price for solar, a Guardian heat pump or both.
Frequently asked questions
How long does it take a heat pump to heat a pool?
A correctly sized heat pump usually takes one to four days to lift a covered pool by about 10°C, depending on pool volume, air temperature and unit size. After that it only replaces daily heat loss, which takes a few hours a day.
Can I heat my pool in a day?
A gas heater can add several degrees in a day. A heat pump can on a smaller or partly warm pool, but a full 10°C lift on a 50,000 litre pool normally takes longer. Solar can't be rushed, it depends on sunshine.
What is the ideal pool temperature?
Most families are comfortable between 26°C and 28°C. Lap swimmers often prefer 25°C to 27°C, while young children, older swimmers and therapy use usually suit 28°C or warmer.
Should I leave my pool heat pump on all the time?
During your swimming season, yes. Holding a steady temperature is cheaper than letting the pool cool and reheating it each time. Use the timer to favour the warmest hours, and keep a cover on overnight.
Does solar pool heating work in September in Adelaide?
Yes, on sunny days, though the lift is smaller than in summer. Solar typically delivers a seven to eight month season in Adelaide. For swimming in the cooler months, a lot of owners add a heat pump to top up.
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