Best Heat Pumps for Cold Climates in Australia: What Actually Works Below 5°C

Most Australian homes can use a standard heat pump hot water system without issue. But if you live in a cold climate zone — the ACT, alpine NSW or VIC, elevated Tasmania, or the New England Tablelands — refrigerant choice matters a great deal. The wrong heat pump in the wrong climate will spend winter running its electric backup element rather than the heat pump cycle, quietly erasing the efficiency advantages you installed it for.

This guide explains why cold temperatures affect heat pump performance, identifies the Australian locations that need a cold-climate capable unit, and ranks the best options available in 2026.

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Why Cold Temperatures Affect Heat Pumps

A heat pump hot water system works by extracting heat from the ambient air and transferring it to your water tank. The refrigerant absorbs heat from outdoor air (even relatively cold air contains heat energy), the compressor raises the refrigerant pressure and temperature, and that heat is released into the water.

When ambient temperature drops, there is less heat energy in the air to extract. The refrigeration cycle becomes less efficient. The COP (Coefficient of Performance) — the ratio of heat delivered to electricity consumed — falls as temperature falls.

For standard refrigerants like R290 (propane) or R513a, this efficiency drop becomes severe below approximately -5°C to -7°C. At these temperatures, many units activate a backup electric heating element — essentially operating as a conventional electric storage system until temperatures rise. This is fine occasionally, but if your climate regularly sees nights below -7°C throughout winter, a standard heat pump will spend months in backup mode and your electricity bill will reflect it.

CO2 (R744) refrigerant behaves differently. CO2 operates at much higher pressures than R290, and its refrigeration cycle maintains effectiveness at temperatures as low as -25°C. The COP does degrade somewhat at very low temperatures, but CO2 units continue operating as genuine heat pumps well into negative double-digit temperatures — without activating electric backup in conditions that would stall an R290 unit entirely.

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Australia’s Cold Climate Zones

Australia’s climate is generally warm, and this sometimes leads people to underestimate how cold parts of the country get. The following regions regularly experience overnight temperatures at or below -5°C during winter:

ACT (Canberra and surrounds): Canberra averages minimum temperatures of -2°C to -6°C in June and July, with the coldest nights reaching -7°C to -9°C multiple times per winter. An R290 heat pump operating near its -7°C limit will be marginal at best through Canberra’s coldest weeks.

Alpine NSW: Jindabyne, Cooma, Bombala, and surrounding areas regularly see temperatures well below -5°C. The Snowy Mountains region is genuinely sub-alpine, and standard heat pumps are poorly suited.

Alpine VIC: Mount Beauty, Harrietville, Bright, and the broader alpine region experience similar conditions to alpine NSW. Falls Creek and Mount Hotham areas are genuinely extreme — CO2 is the only appropriate choice.

Elevated Tasmania: Highland areas, the Central Plateau, and inland elevated areas can reach -5°C to -10°C regularly in winter. Coastal Tasmania (Hobart, Launceston) is milder but can still see frost nights below -5°C.

New England Tablelands: Armidale and Glen Innes in northern NSW sit at 1,000m+ elevation and experience regular frosts and occasional -5°C or below nights despite being in the nominally warm northeast of the country.

Most Australian coastal cities are fine with standard heat pumps. Sydney, Melbourne, Brisbane, Adelaide, and Perth rarely or never reach -5°C. For these locations — and most of inland NSW, QLD, WA, and SA — a standard R290 heat pump like the iStore 270L is perfectly adequate.

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CO2 (R744) vs R290 in Cold Climates

	CO2 (R744)	R290 (propane)
Minimum operating temp	-25°C	-7°C (typical)
Rated COP (standard conditions)	5.0	4.8
COP at -10°C	~4.0–4.5	Backup element activates
System type	Split system	Typically integrated
Price (unit, before install)	$5,000–$5,800	~$2,790
Installed cost	$7,000–$9,500	$4,000–$5,500

At -10°C ambient, a CO2 heat pump is still operating as a heat pump with a COP of roughly 4.0–4.5. An R290 unit at -10°C has activated its electric backup and is operating with a COP of 1.0 — the same as a basic resistive element hot water system with no heat pump advantage whatsoever.

Over a Canberra winter with 60 nights below -5°C, the difference in electricity consumption between a CO2 heat pump and an R290 unit in backup mode is substantial — easily hundreds of kilowatt-hours per winter, costing $50–$150/year at current tariffs. The $2,000–$3,000 premium for a CO2 unit pays back faster in cold climates than it does in Sydney or Brisbane.

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Best Cold Climate Heat Pumps in Australia 2026

#1 Reclaim Energy CO2 250L

The Reclaim Energy CO2 250L is the most popular cold-climate heat pump in Australia. It is Australian-designed and uses CO2 (R744) refrigerant in a split system configuration.

Key specs:

• Refrigerant: CO2 (R744)
• Rated COP: 5.0
• Minimum ambient: -25°C
• Tank capacity: 250L
• System type: Split (compressor unit separate from tank)
• Unit price: ~$5,000 before installation
• Installed cost: ~$7,000–$9,000

The split design means the compressor can be positioned in a sheltered spot — under an eave, in a garage, or in a position that offers some protection from the worst overnight temperatures — while the tank sits indoors or in a less exposed location. This practical flexibility is genuinely useful in cold climates.

Reclaim has an established Australian service network and a strong reputation for reliability. Their warranty covers 5 years on the compressor and tank.

View the Reclaim Energy CO2 250L product page and our full Reclaim Energy heat pump review.

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#2 Sanden Eco Plus 250L

The Sanden Eco Plus 250L is a Japanese-designed CO2 heat pump with a stainless steel tank and strong long-term reliability reputation.

Key specs:

• Refrigerant: CO2 (R744)
• Rated COP: 5.0
• Minimum ambient: -25°C
• Tank capacity: 250L
• System type: Split
• Unit price: ~$5,800 before installation
• Installed cost: ~$7,500–$9,500

The stainless steel tank is Sanden’s flagship differentiator. Most heat pump tanks use vitreous enamel (glass-lined) construction; stainless steel has superior corrosion resistance and a longer practical service life, particularly in areas with harder water. Sanden offers a 7-year warranty on the heat exchanger, which is best-in-class.

The Sanden is the premium option at a premium price. For buyers in cold climates who want the most durable, longest-warranty system available in Australia, it is the top choice.

View the Sanden Eco Plus 250L product page and our full Sanden Eco Plus review.

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#3 iStore 270L (R290) — For Mild Cold Climates

For locations that experience occasional frost but do not regularly drop below -7°C, the iStore 270L is a cost-effective alternative to the CO2 systems.

Key specs:

• Refrigerant: R290 (propane)
• Rated COP: 4.8
• Minimum ambient: -7°C
• System type: Integrated (all-in-one)
• Unit price: ~$2,790 before installation

The iStore’s -7°C minimum is better than most R290 competitors (Rheem AmbiHeat is rated to -5°C) and is adequate for most of coastal VIC, most of ACT’s urban areas on average winter nights, and the majority of elevated inland locations that see light frosts but not sustained sub-zero periods.

If your location has the occasional -8°C night but averages -2°C to -4°C in the coldest months, the iStore is a reasonable choice at a substantially lower price than CO2. If your coldest nights consistently reach -7°C or below, CO2 is the safer long-term choice.

Read our full iStore heat pump review for a complete assessment.

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What to Look for in Cold Climate Specs

When evaluating a heat pump for a cold location, the marketing brochure is not enough. Look for:

Minimum ambient temperature rating: The actual published number, not “suitable for most climates” language. -5°C is meaningfully different from -7°C in Canberra. -25°C is meaningfully different from -7°C in Jindabyne.

Whether a backup element exists and at what temperature it activates: Some brands activate backup at -5°C; others at -10°C. A CO2 unit may have a backup element but never activates it in Australian conditions. An R290 unit may activate backup on any winter night in Canberra.

COP at low temperature, not just rated COP: Manufacturers quote COP at standard test conditions (typically 20°C ambient). Ask for or look up the COP curve at lower temperatures. A unit with COP 5.0 at 20°C and COP 1.0 at -8°C is not a COP 5.0 heat pump for a Canberra winter.

Installation requirements for cold climate placement: Split systems offer installation flexibility. Integrated units must be sited in ambient air — consider whether your installation location will be exposed to the worst winter nights.

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Split vs Integrated Systems for Cold Climates

For genuinely cold locations, the split system design of the Reclaim and Sanden is a practical advantage beyond just refrigerant chemistry.

With a split system, the compressor unit (which houses the refrigerant circuit) can be installed in a sheltered position — under a carport, in an enclosed garage with ventilation, or against a wall with some protection from prevailing winds. This can make a meaningful difference to the ambient temperature the compressor actually experiences versus the open-air temperature recorded by a weather station.

The tank in a split system is typically installed indoors or in a protected location, eliminating standby heat loss from a hot tank sitting in cold outdoor air.

Integrated (all-in-one) systems must be sited entirely outdoors or in a well-ventilated space, fully exposed to ambient temperatures. In cold climates, this is a disadvantage. The iStore’s all-in-one design is perfectly fine for most of Australia but is a consideration in genuinely cold locations.

The trade-off is installation complexity and cost. Split systems require a refrigerant line run between the compressor and tank, which adds to installation time and cost (typically $500–$1,500 more than an integrated install of comparable capacity).

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Running Cost Difference in Cold Climates

A CO2 heat pump in Canberra uses significantly less electricity than an R290 heat pump in Canberra during winter. The difference is not the marginal COP 5.0 vs COP 4.8 comparison that applies in Sydney — it is the difference between COP 4.0–4.5 (CO2 operating as a heat pump at -5°C) and COP 1.0 (R290 backup element activated at -5°C).

Rough annual electricity cost comparison (Canberra, 250L tank, family of 4):

System	Winter COP (approximate)	Annual electricity cost (approx)
CO2 heat pump (Reclaim/Sanden)	4.0–4.5 (maintains heat pump mode)	~$250–$350/year
R290 heat pump (in backup mode through coldest nights)	Effective ~2.0–2.5	~$450–$600/year
Electric storage (no heat pump)	1.0	~$900–$1,200/year

The running cost difference between CO2 and a standard R290 unit in backup mode is approximately $150–$250/year in a cold climate like Canberra. Over 10 years, this is $1,500–$2,500 — which covers a meaningful portion of the CO2 premium ($2,000–$3,000 more installed vs iStore). In cold climates specifically, the CO2 units’ payback calculation is more favourable than it appears in mild climates.

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Conclusion

For the majority of Australians — coastal cities, inland warm climates, most of Queensland, WA, SA, NSW, and VIC — a standard R290 heat pump like the iStore 270L is excellent value and more than adequate for the climate.

For the ACT, alpine NSW and VIC, elevated Tasmania, and the New England Tablelands, a CO2 heat pump is the correct long-term choice. The Reclaim Energy CO2 250L is the most accessible option ($5,000 unit, $7,000–$9,000 installed). The Sanden Eco Plus is the premium option with a stainless steel tank and best-in-class warranty.

Buying the wrong refrigerant for your climate is an expensive mistake — a standard heat pump that spends six months per year in electric backup mode is not a heat pump in any meaningful sense for that period. Get the cold climate decision right from the start.

For the full field of heat pump options across all climate zones, see our heat pump hot water hub and complete heat pump guide. For current rebates, see our heat pump rebate guide.