Feeling the heat: maximising heat pump efficiency at home

Australia has seen a sustained increase in the uptake of heat pump installations throughout 2023, with consumers turning to more sustainable options to replace existing gas and electric heating systems. However, in order to maximise the efficiency of these systems and reduce costs in a tough financial climate, there are several factors consumers need to consider when it comes to choosing, installing and using their heat pumps at home.

With colder weather approaching on the horizon, many Australians will be about to enter their first cooler season with a heat pump system installed in their home, or will be considering which heat pump solution will best meet their needs. While heat pump technology, such as reverse cycle air conditioning, has seen a steady rise in recent years, Australia has also seen a rapid uptake of heat pump hot water systems, with the Clean Energy Regulator reporting a total installation of 94,000 systems over the first three quarters of 2023 alone.(1)

The recent increase in the uptake of heat pump technology in Australia can in part be attributed to government financial incentives to install cost-effective and energy efficient equipment in Australian homes, with many consumers jumping at the opportunity to ease the pressure on their pockets and minimise their environmental impact.

Choosing the right heat pump

Heat pumps, as opposed to conventional heating options, transfer and amplify heat rather than generating it. The energy output from these systems is considerably higher than the energy needed to power them, making them an efficient alternative, particularly when paired with rooftop solar.

However, heat pumps are not a one-size-fits-all solution — to reduce costs and maximise comfort, selecting the right model for the space is imperative.

Air-source heat pumps

One of the biggest mistakes that consumers make when selecting a heat pump to control indoor air temperature is size. Installing an oversized pump can make heating unnecessarily expensive and lead to problems with moisture in humid climates.

Heat pumps that are too powerful will push large amounts of hot or cool air into a space in a short period of time, turning on and off repeatedly to meet a set temperature. This not only requires more energy, but also reduces the lifespan of the system by working it unnecessarily hard. In these cases, because the system isn’t running long enough to properly dehumidify the space, it can also lead to rooms feeling cold and wet, creating the perfect environment for mould.

The size that a user selects should match their heating needs, while also taking into consideration how large and airtight the home is, the climate and the number of residents. As a general rule, consumers should select a minimum capacity system to meet the home’s cooling load on its warmest days.

To select the right system, consumers need to accurately determine their heating and cooling loads through conversations with their contractor or an energy consultant, or can calculate these themselves using a range of online estimating tools that are available for this purpose.

Heat pump hot water systems

When it comes to choosing a heat pump hot water system, users should also speak with an energy consultant about factors such as the size and flow rate required, particularly if they are going with a tankless water heater. It’s also important to consider how many hot water appliances will need to work simultaneously and what water temperature will be required from these appliances to allow them to function appropriately.

Another consideration is the heater’s first-hour rating, which refers to the output of hot water the pump can manage every hour, starting with a full tank. This will differ depending on the size of the tank and the environment it’s being used in. The greater the capacity of the tank, the more hot water will be produced, so finding a tank that accurately meets the household’s needs will be both convenient and cost-effective.

Intelligent installation

After identifying which pump best suits their requirements, users should consider the importance of correct, professional installation to maximise efficiency and performance.

Heat pump installation requires expert electrical and refrigerant handling and needs to meet a set of standards and regulations. Although it may seem cheaper to take on a DIY installation, professionals warn against it, with incorrect wiring and handling of materials or faulty sealing of ductwork leading to significantly impacted performance, increased running costs and non-compliance with regulations and warranty requirements.

System settings

While the selection and setup of a heat pump is an important start to ensuring efficiency, consumers can see significant ongoing benefits to cost and operation by understanding how to use their system’s settings.

Air-source heat pumps

While it may seem easiest to trust the system’s ‘auto’ mode, this can cause the system to regularly switch between heating and cooling modes, which requires more energy. Air source heat pumps will run more efficiently if they are set to the ‘heat’ setting in cold weather and the ‘cool’ setting in warmer months.

It can be tempting to turn the temperature on a heating/cooling system up and down depending on the outside temperature or the time of day. However, a heat pump will work most effectively by maintaining a set, comfortable temperature. A low setting of between 18 and 20 ̊C is generally recommended to keep a space comfortable.

Heat pumps are most efficient in a space when they’re used for as much of its heating as possible. Users may benefit from experimenting with opening doors to expand the system’s reach and closing off areas which don’t need heating at certain times of the day. To heat a large space efficiently, it’s recommended to increase the fan speed to a higher setting.

While legend has it that leaving a heat pump running all day could boost efficiency by preventing a heat pump from working harder to repeatedly heat or cool a space, the consensus amongst professionals is that the numbers just don’t add up. For the longevity of the system and for users’ wallets, it’s beneficial to turn a system off if it’s not being used.

It’s also worth noting that spaces with better insulation will better maintain temperature and, in turn, increase the heat pump’s efficiency.

Heat pump hot water systems

The prime temperature range for heat pump hot water systems is generally considered to be between 49 and 60 ̊C. This is because heat pump systems work better with a higher water temperature which allows them to extract heat from surrounding air more effectively.

This temperature is also optimal for general household usage, providing a safe and comfortable temperature for showers and an effective temperature for washing machines and dishwashers.

As well as choosing a water temperature that is efficient and effective, it’s important that consumers select a temperature range that’s safe. This range is proven to prevent the growth of dangerous bacteria such as legionella, and will also prevent scalding.

Maintenance management

According to research(2) from the Department of Energy in the US, the difference in energy consumption from a properly maintained heat pump and one that has been extremely neglected, can range from ten to 25 per cent.

Users can combat this by undertaking regular at-home maintenance. Dirty filters can significantly reduce airflow, so cleaning air filters, as well as removing any debris, plant matter and clutter from around the outdoor heat pump, will prevent obstructions and maximise the efficiency of a unit. If maintenance is neglected in an ongoing way, it can lead to the system’s compressor becoming damaged, so it’s important to undertake monthly cleaning maintenance.

As well as regular home maintenance, heat pumps should be professionally serviced at least once a year. A licensed professional will diagnose problems and undertake maintenance to correct them. This may include: