How Loud Are Air Source Heat Pumps?
How Loud Are Air Source Heat Pumps?
Noise is a common concern for homeowners considering an air source heat pump, particularly when the outdoor unit will be positioned near a bedroom, patio or neighbouring property.
So, how loud are air source heat pumps?
Modern air source heat pumps are designed to operate at relatively low sound levels, but there is no single noise figure that applies to every system. The sound you actually hear depends on the heat pump model, how hard it is working, where it is installed and the surrounding environment.
If you are considering making the switch, you can explore BPC Heat's range of air source heat pumps.
What Does an Air Source Heat Pump Sound Like?
An air source heat pump contains a fan, compressor and other moving components, so some operating noise is normal.
Rather than the combustion noise you might associate with a traditional boiler, the outdoor unit generally produces a steady mechanical hum combined with the sound of air moving through the fan.
The exact sound varies throughout operation. A heat pump may run more quietly when heating demand is low and work harder when the property requires more heat.
Manufacturers have also continued to develop quieter outdoor units. Mitsubishi Electric, for example, specifically highlights low noise as a feature of its Ecodan air source heat pump range.
How Is Heat Pump Noise Measured?
Heat pump noise is normally expressed in decibels using an A-weighted measurement, or dB(A), which accounts for how the human ear responds to different frequencies.
When looking at technical information, you may also see two different measurements:
Sound Power Level
Sound power describes the total acoustic energy produced by the heat pump itself.
It is useful when comparing different units because it relates to the source of the noise rather than where someone is standing.
Sound Pressure Level
Sound pressure describes the noise measured or calculated at a particular position.
This is affected by factors including:
- Distance from the heat pump
- Nearby walls and reflective surfaces
- Buildings and solid barriers
- The position of neighbouring windows
- The location of the outdoor unit
This is why simply comparing one decibel number between two heat pumps does not always tell you how loud either system will actually sound once installed.
Current MCS noise assessment guidance specifically takes the manufacturer's sound power level, distance, reflecting surfaces and barriers into account when calculating sound at an assessment position.
What Makes an Air Source Heat Pump Sound Louder?
Several factors can affect how noticeable a heat pump is.
Where the Outdoor Unit Is Positioned
Location is one of the most important considerations.
A heat pump positioned directly beside a bedroom window or in a confined space may be more noticeable than one installed in a suitable open area further away.
Nearby walls can also reflect sound. MCS guidance accounts for the number of reflective surfaces around an outdoor heat pump when assessing noise.
Distance
Sound generally becomes less noticeable as you move further away from the source.
This means the distance between the outdoor unit and neighbouring properties or frequently occupied rooms should be considered when planning the system.
The Heat Pump Model
Different heat pumps have different acoustic characteristics.
Always check the manufacturer's technical data when comparing units rather than assuming every heat pump will produce the same amount of noise.
Heating Demand
A heat pump does not necessarily operate at exactly the same output all day.
Fan and compressor speeds can change depending on the heating demand, outdoor conditions and system controls, meaning the sound can vary during normal operation.
Are Air Source Heat Pumps Louder in Cold Weather?
They can sound different when outdoor temperatures fall because the system may need to work harder to meet the property's heating demand.
Cold and damp conditions can also cause frost to develop on the outdoor heat exchanger. Modern air source heat pumps manage this using an automatic defrost cycle, during which the fan or compressor behaviour may temporarily change.
This is a normal part of heat pump operation.
For more information about winter performance, read our guide: Do Heat Pumps Work in Cold Weather?.
Can You Hear an Air Source Heat Pump Inside the House?
Whether the outdoor unit can be heard indoors depends on several factors, including its location, the construction of the property and the distance from windows and bedrooms.
Correct positioning can make a significant difference.
The outdoor unit should also be installed in accordance with the manufacturer's required clearances. Trying to hide a heat pump inside a small enclosure without considering airflow and manufacturer guidance is not recommended, as restricted airflow can affect operation.
How Can Heat Pump Noise Be Reduced?
Good system design is one of the best ways to minimise unnecessary noise.
Considerations include:
- Selecting an appropriately sized heat pump
- Choosing a model with suitable acoustic performance
- Positioning the outdoor unit carefully
- Maintaining the manufacturer's required airflow clearances
- Avoiding unnecessary sound reflection from enclosed areas
- Using appropriate anti-vibration mounting where required
- Keeping the unit properly maintained
Solid barriers can sometimes reduce sound reaching a particular position, but any solution must maintain the airflow and clearances required by the heat pump manufacturer.
Does Heat Pump Size Matter?
Correct sizing is important for both heating performance and system operation.
A heat pump should ultimately be selected according to the calculated heat loss of the property rather than simply choosing the largest available unit.
Factors including floor area, insulation, glazing, desired room temperatures and local winter conditions all influence how much heat the property requires.
Getting the system design right helps ensure the selected heat pump can meet demand efficiently without relying on an unnecessarily oversized unit.
Find the Right Air Source Heat Pump with BPC Heat
If you are planning an air source heat pump system, BPC Heat offers several ways to help you select the right equipment for your property.
Get a Free Heating Design
For a more detailed project, submit your plans through the BPC Heat Design Service.
Your property information can be reviewed to help determine the heating solution and equipment required for the project. BPC Heat currently offers design support for heat pumps, underfloor heating, radiators and combined heating solutions.
Get an Instant ASHP Quote
If you are looking for an initial indication of system size and price, use the Instant ASHP Quote.
Enter details including the property floor area, number of occupants and property type to receive an initial heat-pump and cylinder recommendation with live kit pricing.
A detailed heat-loss calculation should still be completed when finalising the design of the heating system.
So, Are Air Source Heat Pumps Noisy?
Air source heat pumps do produce sound, but a modern system should not automatically be considered noisy.
How noticeable a heat pump is depends on the model, operating conditions, distance from the listener and, importantly, where the outdoor unit is positioned.
Checking manufacturer sound data and considering noise as part of the system design can help ensure the heat pump is suitable for both the property and its surroundings.
When comparing systems, look beyond a single decibel figure. Correct sizing, product selection and thoughtful positioning all contribute to a heating system that performs effectively without creating unnecessary noise.
