Does it work in winter?
Yes — all CEC-listed units operate down to 5°C ambient, and most work to -5°C. Cold-climate models (Reclaim, Sanden CO₂) work to -10°C. In southern Tasmania we recommend a CO₂ unit.
Education
How heat pump hot water works (in plain English)
No jargon, no sales pitch. Just the physics, the numbers, and the trade-offs so you can decide whether a heat pump is right for your home.
Live diagram
Watch the cycle in motion
The fan pulls warm outdoor air across an evaporator coil. A small compressor concentrates that warmth, and the condenser coil wrapped around your tank transfers it straight into the water. For every 1 kWh of electricity the compressor uses, 3–5 kWh of heat enter your tank.
- • Yellow dots = refrigerant gas circulating through the loop.
- • Blue arrows = ambient air being drawn in by the fan.
- • Orange shimmer = heat rising through the tank water.
Ambient air Refrigerant gas Hot transfer Hot water
Refrigerant absorbs warmth from outdoor air, the compressor concentrates it, and the condenser coil transfers that heat into your tank. The cycle repeats until the water hits 60°C.
The big idea
A conventional electric hot water system works like a giant kettle: it uses electricity to directly heat an element inside the tank. For every 1 kWh of electricity in, you get roughly 1 kWh of heat out.
A heat pump doesn’t make heat. It moves heat — from the air outside your home into the water in your tank. Because moving heat is much easier than creating it, for every 1 kWh of electricity you put in, you get 3 to 5 kWh of heat out. That ratio is called the Coefficient of Performance, or COP.
Why this matters for your bill
If your old electric system uses 12 kWh a day to heat water, a heat pump with a COP of 4 only needs about 3 kWh. At 30c/kWh that’s a difference of $985 a year — before solar.
The four-step refrigerant cycle
- 1
Evaporator (outside)
A fan blows air across a coil filled with a refrigerant that boils at -26°C. Even on a cool morning, the air is warm enough to boil it into a gas — absorbing heat in the process.
- 2
Compressor
A small electric compressor squeezes that gas, raising its pressure and temperature dramatically — to around 70–80°C.
- 3
Condenser (inside the tank)
The hot gas runs through a coil wrapped around your storage tank. Heat transfers into the water, and the refrigerant condenses back to a liquid.
- 4
Expansion valve
The liquid passes through a valve that drops its pressure, cooling it down so it can start the cycle again.
What this looks like at your house
Most Australian homes use an integrated unit: the compressor sits on top of (or beside) the storage tank in one tidy outdoor enclosure. A few premium brands use a split system, where a small outdoor unit connects to an indoor tank — useful in tight courtyards or apartments.
Common concerns, honestly answered
Is it loud?
Quality units run at 37–48 dB(A) at 1 metre — quieter than a normal conversation. Place it 1m+ from bedroom windows and you’ll never notice it.
Is the water hot enough?
Tanks heat to 60°C, which kills Legionella bacteria. A tempering valve mixes it down to 50°C at the tap, exactly like your old system.
How much electricity does it use?
Around 2–4 kWh per day for a family of four. A 6.6 kW solar system on a sunny day produces more than 10× that.
Does it need clearance?
Most units need 30–60cm of free air on the fan side. Your installer will check this during the site quote.
How long does it last?
Tanks: 10–15 years with standard warranty. Compressors: 6–10 years. Replacement parts are widely available across Australia.
More questions? See our full FAQ or head straight to the buying guide.
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