Air source heat pumps are used to provide heating, cooling and domestic hot water and achieve this by transferring heat between the inside and outside of a home.
This movement of heat, rather than generation of heat through combustion of fuels as with other main types of heating systems, helps air source heat pumps to be a fantastic way to serve a home for the foreseeable future, among a range of other benefits.
However, air source heat pumps aren’t without their flaws and can prevent them from being more commonplace in homes.
The main problems with air source heat pumps can include:
- Their typically high purchase and installation costs
- Can be noisy
- Less efficient as outside temperatures fall
- Can be more onerous to install
- Can be affect by inclement weather
- Require a constant electricity supply
- Not entirely carbon-neutral
- Poor placement can affect performance
- Not the most aesthetically pleasing
- Slower heat output and lower temperatures
- Requires sufficient internal apparatus to make the most out of
We’ve been using our own air source heat pump (ASHP) to provide heating and hot water for our home for over 5 years and while we’ve never had any issues with it, we understand the limitations of a heat pump and what issues must be overcome to make them worthwhile.
We discuss these main problems with air source heat pumps in more detail below using our own heat pump as an example.
Air source heat pumps aren’t as mainstream as other heating systems, like gas boilers, and so their upfront costs for purchase and installation can be higher compared to these more traditional heating systems.
Due to these costs, some people find it easier and cheaper to continue using their old heating system and costs can therefore be a barrier to ASHPs being installed in more homes.
While our air source heat pump system was installed when our house was built, it would have been a relatively expensive install compared to what a traditional gas boiler installation would have cost.
Costs can also increase when installing in an older home as poorer home insulation levels can affect heating performance. If there’s a need to upgrade or even replace an existing heating system, such as radiators, this can increase installation costs further.
While air source heat pumps can be expensive purchases in the short-term, they should be viewed as long term investments as these upfront costs can be recuperated over time, through running costs, over the lifetime of the heat pump, which can be up to 20 years or more.
See our article on how much an air source heat pump can cost to buy, install and run for more information.
External air source heat pump units are electrical appliances and use fans to force air through them to extract heat energy from the air.
Air source heat pumps don’t always run all the time and only operate when needed.
At reasonable outside temperatures and when operating, an air source heat pump can make a small amount of noise, but can be unnoticeable when you’re moved away from the heat pump.
At lower temperatures where there’s less heat within the air, an ASHP can need to work harder and for longer in order to generate the same desired indoor temperatures.
This can increase noise levels and is why air source heat pumps are typically located down the side of a house, out the way of any windows and far away enough from neighboring properties. Noise levels from an ASHP will need to be considered during unit placement at installation.
Modern, smaller units from a reputable brand can be less noisy overall compared to older heat pumps, and it may be possible to build an enclosure around an ASHP to help reduce noise levels, subject to airflow not being compromised.
Our article on air source heat pump noise explores this topic further and includes a video of what our air source heat pump sounds like.
Air source heat pumps can work best in moderate to warm climates as the temperature difference between indoors and outdoors can be less, meaning that less energy is required to heat or cool.
However, as temperature drop very low, an air source heat pump can struggle to maintain the same indoor temperatures.
For example, the graph below shows how the heat output from our heat pump lowers as outdoor air temperatures fall.
Our air source heat pump is able to work down to –20°C (-4°F), and as temperatures don’t reach this low in our climate, we haven’t needed to worry about our heat pump not performing.
In colder temperatures, our ASHP may simply need to work for longer to keep up with demand, but energy usage can increase and this can lower the overall COP (coefficient of performance) as a result, which is how much heat energy can be generated from every unit of electrical energy consumed.
If you live in an area with harsh winters, then you might want to consider installing a backup heating system, such as a boiler, to use alongside your air source heat pump. This can work as a hybrid system where an ASHP can be used until temperatures reach too low to operate.
For further information see our articles on how reliable air source heat pumps can be and how air source heat pumps can still work in winter.
Air source heat pump units need to be installed outside to work and choosing the right location for an install can be more difficult than other types of heating systems.
For example, and air source heat pump should be installed:
- Away from windows and neighbors for noise purposes.
- On vibration mounts to help reduce vibration and noise
- Close to a property for reduced pipe length but far enough away from walls or overhangs for airflow purposes.
Our air source heat pump is installed down the side of our house and is the perfect location, but it may not always be possible to find the perfect placement for a heat pump for every household.
Refrigerant pipes will also need to be installed into a home, and the length and number of pipes can depend on factors such as the type of heat pump, size of home, and number and location of indoor units.
Although heat pump technology has come a long way in improving its installation processes, it’s still always advised to hire an accredited installer.
Our article on where to install and air source heat pump provides more information.
Air source heat pumps should be placed out of high winds as this can affect performance.
Similarly, in areas that may experience heavy snowfall, an ASHP may need to be installed further off the ground as it can compromise airflow and therefore also performance.
For example, the manual to our air source heat pump explains to install it higher up if to be used in a location that experiences heavy snowfall.
It may also be required to mount an air source heat pump on a wall to help mitigate problems arising from harsh weather conditions.
Heat pumps may also be susceptible to corrosion when placed in areas with high concentrations of salt.
Air source heat pumps are electrical appliances and therefore require a constant supply of electricity to work.
Electricity is used to power the fan(s), compressor, and any other electrical components.
Our heat pump takes electricity from our home’s mains electrical supply.
Find out more in our article on air source heat pumps and electrical power.
Although heat pumps are very eco-friendly, they still require electricity to run, and that electricity may not always come from a renewable energy source, depending on how the energy provider has sourced the generated the electricity.
To provide a carbon-neutral solution for the running of an air source heat pump, consider investing in local electricity generation from a renewable energy source, such as solar panels.
An upside to air source heat pumps is that they don’t directly burn fossil fuels such as gas or oil to generate heat, and work by moving heat indoors from heat energy stored naturally within outside air.
The placement of an external air source heat pump unit is important as installing one in a location that doesn’t meet the manufacturer’s guidelines can affect its performance.
The most important factors when locating an ASHP unit can be:
- Keeping out of direct sunlight and away from other forms of heat
- Ensuring the unit is out of places that can experience high winds
In terms of sunlight, the manual for our heat pumps states to:
If our heat pump needs to be installed location that experiences high winds, then our manual also explains to:
An air source heart pump still needs to be placed in an open area however, as nearby objects can affect airflow, which can also affect performance.
Although installing an air source heat pump can bring a host of benefits for a home, they may not always be the best thing to see when located up against a house.
Air source heat pump units can often be large and bulky and may resemble commercial air condition units.
The image below shows our air source heat pump alongside one of our air conditioning units for comparison.
However, many air source heat pump units can be found to be more aesthetically pleasing than our own.
10. Slower Heat Output & Lower Temperatures
Air source heat pumps work differently compared to other forms of heating in that they move heat from one place to another instead of generating heat from the combustion of fossil fuels.
While burning fuels such as gas or oil to generate heat can provide more instantaneous heat at higher temperatures, emissions are created as part of that process.
Air source heat pumps extract heat stored naturally within the outside air and this process can take longer, and the temperatures generated may not be as high.
The image below shows the maximum heating and cooling temperatures for our particular model of heat pump:
However, using an air source heat pump is still a reliable way to provide heating for a home, but it must be understood that an ASHP will need to work for a longer period of time in order to generate the same desired indoor temperatures as other heating systems.
11. Must Be Used With Sufficient Indoor Apparatus
As air source heat pumps provide lower temperatures over a longer period of time, they must be used with the right indoor heating apparatus to allow a heat pump to heat a home as effectively and efficiently as possible.
Using a new ASHP with older, outdated internal heating equipment that isn’t sufficient for use with how a heat pump works can mean indoor temperatures not rising as high as expected.
Pairing an air to water heat pump with large surface area indoor heating equipment such as modern radiators and underfloor heating, alongside ensuring the property is adequately insulated, will help make the most of these lower heat output and lower temperatures.
Our home uses underfloor heating on the lower floor, with each room controlled by its own thermostat for individual heat regulation.
Upstairs is served by numerous and large radiators.
Problems With Air Source Heat Pumps
Although air source heat pumps are a good investment in terms of long-term energy savings and increased comfort, they aren’t without their problems.
Before installing an air source heat pump its always important to consider their downsides to better understand how they can be overcome.
For the best results, hire a professional installer to help you choose the right system and place it in an ideal location. This will help to ensure that a heat pump works to its maximum capacity and can last for its full life expectancy.