One of the most common questions we receive about heat pump hot water systems is how they perform in cold climates. Especially from customers who live in areas like the Southern Highlands, Tasmania, or inland Victoria, where winter temperatures can get pretty frosty.
The short answer? Modern systems are far more efficient than many people think. In this blog, we’ll break it down further and dispel common myths, as well as explore how to choose the right system for your climate. But first, let’s take a crash course in how exactly heat pump systems work.
We understand some readers may be unaware of how these heat pumps work. Put simply, a heat pump hot water system works like a reverse refrigerator. It draws in ambient air, extracts the heat energy, and uses that to heat water stored in a tank. So we can understand why people often ask us how they perform in cold climates, given that the process involves using the air.
While the process is powered by electricity, it’s much more energy efficient than traditional electric or gas systems because it moves heat rather than creating it.
There are two main types of heat pumps:
Air-source hot water heat pumps are a smart choice, as they are compact, easy to install, and work well with great energy efficiency in most Australian climates. This includes even cooler climates (provided the right model is selected).
This isn’t to say heat pump water heaters don’t come without their challenges, especially when it comes to operating in chilly temperatures.
Because air-source heat pumps rely on extracting warmth from the surrounding air, it makes sense that their efficiency naturally drops as the outside temperature does. It just means the system has to work harder, typically from 5°C and below. And once it nears 0°C, the system has to work especially hard to absorb enough heat. This can slow down recovery times and increase electricity use.
But here’s where heat pump systems really shine. To overcome this, many modern systems include backup heating boosters. Like a backup generator during a power outage, these automatically kick in during extreme cold or high-demand periods to ensure there’s always a reliable supply of hot water. While the system might not be as efficient when not relying on the booster, it’s a valuable safety net that will get you through the winter.
Let’s delve further into how today’s heat pump hot water systems technology has evolved to handle colder climates better than older models.
One of the main challenges in cold weather is frost forming on the evaporator coil. This reduces heat exchange efficiency. But modern systems use automatic defrost cycles to detect and melt frost before it affects performance. Clever, right? Not only that, but the cycles are energy-conscious and timed to run only when necessary, which ensures minimal impact on overall efficiency.
Newer heat pump models are equipped with high-efficiency compressors and low-temperature refrigerants that operate more effectively in sub-5°C environments. These improvements help maintain stable performance without overloading the system, even during chilly mornings and frosty nights.
Several manufacturers now offer systems specifically designed for Australian cold climates. They are engineered with enhanced insulation, larger heat exchangers, and better performance down to 0°C or lower. In the Australian market, look at brands like Stiebel Eltron, Sanden Eco Plus, EvoHeat, Rheem, and Quantum Energy, which offer cold-climate variants designed for southern and inland regions.
So, how’s their efficiency compared to other times of the year? The best way to measure this is using a term called COP, which stands for Coefficient of Performance. Put simply, the COP tells you how much heat energy the system produces compared to the electrical energy it uses.
For example:
A COP of 3 = 3 kWh of heat produced for every 1 kWh of electricity consumed
The above is considered incredibly energy efficient. It’s typical for a heat pump system to achieve a COP of 3 to 4 during warmer seasons. However, during winter, especially in colder Australian regions, the COP can drop to around 2 or lower because the unit is working harder to extract heat from the cooler air. But as we’ve discussed, newer models with smart sensors and backup elements that kick in only when needed will still perform well.
Is there anything you can do to increase the efficiency of your heat pump hot water system in cold weather? Yes, but it mainly comes down to the choice and installation of your system.
A unit that’s too small for your household will struggle in winter. Check with an expert to ensure your system is the right size for your needs and climate.
A quality hot water systems installer will know to install the unit in a sunny, sheltered spot with good airflow. Ideally, this should be on the northern side of your home, which will help it draw in warmer air during winter.
Something you can do is clear away leaves and debris around the system, and ensure vents and coils are free from blockages. Additionally, regular servicing always helps to maintain efficiency and ensure longevity.
Allow built-in defrost cycles to run properly. Don’t cover or obstruct the unit, as this can trap frost and reduce performance.
So, are there better alternatives for cold climates where heat pump systems may struggle to perform? Let’s take a look at all the different types of traditional hot water systems and how they compare.
Solar hot water systems have become increasingly popular due to their use of the sun’s energy. Solar can also come with electric or gas boosters as a fall-back in cooler regions. The booster kicks in during cloudy or frosty periods, ensuring consistent hot water. Due to the solar setup, upfront costs are higher, but long-term cost savings and environmental benefits make solar an increasingly popular option, especially in sunny climates.
Conventional electric water heaters are reliable and simple, but tend to be less energy-efficient than heat pumps or solar. They can be a good fallback for areas with limited sun or airflow, but can be more expensive if not run on off-peak tariffs.
Gas hot water systems, which come in either storage or continuous flow, perform reliably in any temperature. However, if you’re sustainability-minded, just know they are not as eco-friendly unless paired with biogas or carbon offsets.
The short answer is yes. Thanks to advancements in heat pump technology, such as refrigerants and smart defrost systems, modern heat pumps can operate efficiently in conditions down to 0°C or even lower.
Just know that during winter, if you’re in a cold climate area, performance may dip slightly, and systems may rely more on backup heating, which can reduce overall efficiency and potentially lead to higher running costs.
Still, if you prioritise energy efficiency, long-term savings, and environmental benefits, a well-installed, cold-climate-rated heat pump can absolutely be worth the investment.
Ultimately, the best system depends on your location, household size, energy preferences, and available infrastructure. A professional installer can assess these factors and recommend the most suitable option.
As mentioned, some reputable brands producing high-performing heat pump systems for Australian cold climates include Stiebel Eltron, Sanden, and Rheem. These manufacturers offer units with enhanced cold-weather capabilities, including improved compressors, efficient defrost cycles, and reliable performance even during freezing temperatures.
When choosing a system for a cooler region, you’ll want to look for models specifically rated for low ambient temperatures. Also, check that they have strong warranties, backup heating options, and high Coefficient of Performance (COP) ratings. And remember, proper sizing and professional installation are also key to getting the most out of your investment.
Not sure where to start? Check out our range of heat pump systems or contact our friendly team for expert advice and a fast quote tailored to your location and household needs.
Yes, modern heat pump hot water systems are designed to operate efficiently in cold weather, especially those built for Australian climates.
Most standard systems operate effectively down to around 0–5°C, while cold-climate-rated models can continue to function efficiently even below freezing.
They can be less efficient in very cold conditions, may require more space, and typically cost more upfront than conventional systems.
Yes, but only if there’s enough ambient air circulation and the space doesn’t consistently drop below the system’s minimum operating temperature.