Guides
How does a heat pump hot water system work?
A heat pump hot water system works like a fridge in reverse. A fan draws in outside air, a refrigerant absorbs its warmth, and a compressor concentrates that heat before passing it into the water tank. Because it moves heat rather than making it, it uses about a third of the power of an electric element.
Heat pumps are the fastest growing type of hot water system in Australia, mostly because they cost so little to run. The technology sounds high-tech, but the idea is one people already have in their kitchen. Terry has fitted a good number of them around Berala and Western Sydney, and he is happy to explain in plain terms how they work before anyone spends the money.
The refrigeration cycle in plain English
A heat pump works like a fridge running in reverse. A fridge pulls heat out of the food compartment and dumps it out the back. A heat pump does the same thing the other way around: it pulls heat out of the outside air and puts it into your water. A fan draws air across a coil filled with refrigerant, the refrigerant soaks up warmth from that air even when it feels cool outside, and a compressor then squeezes the refrigerant, which concentrates that gentle warmth into real heat. That heat is passed into the tank, and the cycle repeats until the water is hot.
Why it uses about a third of the power
An ordinary electric tank makes heat by pushing current through an element, a bit like a giant kettle. That is why it is dear to run. A heat pump does not make heat, it moves heat that is already in the air, and moving heat takes far less energy than creating it. In numbers, plumbers talk about the coefficient of performance, or COP. A COP of around three means roughly three units of heat delivered for every one unit of electricity used. That is where the figure of about a third of the running cost comes from, and it is the whole reason people fit them.
How it behaves in cold weather
There is an honest trade-off. Because a heat pump draws warmth from the surrounding air, it works harder and slower when that air is cold, so on a frosty winter morning it is less efficient than on a mild day. Sydney's climate is gentle enough that this is rarely a problem, but it is good to know. Quality models handle cold air well, and many include a small electric booster for the coldest snaps. The main lesson is sizing: an undersized heat pump gets exposed in winter, so Terry sizes for the household and the season, not just the sunny days.
Noise, siting and rebates
A heat pump has a fan and a compressor, so it makes a low hum while running, similar to an air conditioner's outdoor unit. That means siting matters. It wants open air around it to breathe, and it is best placed away from a bedroom window or a neighbour's, ideally running during the day rather than overnight. On cost, a heat pump runs roughly $3,500 to $5,500 before rebate, more than a plain tank. This is where the rebates change the maths. In NSW, replacing an old electric or gas system with a heat pump can combine federal certificates with the state incentive to save roughly $1,000 to $2,500, applied as an up-front discount at installation through accredited suppliers, so there is no rebate to chase afterwards. That can bring the real price down close to a good tank, while the running cost stays far lower.
Terry will give you a straight answer on whether a heat pump genuinely stacks up for your home, or whether a gas system makes more sense, and he will point you to how the rebate is applied. Hot water and electrical work must be done by licensed tradespeople, so it is not a DIY job. For an honest assessment and a fixed quote, call Terry on 0415 274 542.
Frequently asked questions
- How does a heat pump hot water system work?
- It works like a fridge in reverse. A fan draws in outside air, a refrigerant absorbs the warmth, and a compressor concentrates that heat and transfers it into the water tank. Because it moves existing heat instead of creating it, it uses far less electricity than a standard element.
- Do heat pumps work in winter?
- Yes, but less efficiently. Because they pull warmth from the air, cold mornings make them work harder and slower. Sydney's mild climate suits them well, and quality models include an electric booster for the coldest snaps. Correct sizing matters most so it keeps up in winter.
- Are heat pump hot water systems noisy?
- They make a low hum from the fan and compressor, much like an air conditioner's outdoor unit. It is not loud, but siting matters. Place it in open air, away from bedroom windows and neighbours, and ideally set it to run during the day rather than overnight.
- How much can I save with a heat pump rebate in NSW?
- Replacing an old electric or gas system with a heat pump can combine federal certificates with the NSW incentive to save roughly $1,000 to $2,500. It is applied as an up-front discount at installation through accredited suppliers, so there is nothing to claim back later.
- Is a heat pump cheaper to run than electric or gas?
- Yes. A heat pump uses about a third of the power of a standard electric element because it moves heat rather than making it, giving it the lowest running cost of any common system. Over its 10 to 15 year life, those savings usually outweigh the higher up-front price.
Related services
Keep reading
Need a hand from a real plumber?
Terry's been sorting plumbing across Berala and Western Sydney since 1986. Call 0415 274 542 for a straight answer and a fixed price.
NSW Licence L10959 · 40+ years experience