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 the outdoor unit is positioned and the surrounding environment.

If you are considering making the switch, you can explore BPC Ventilation's range of air source heat pumps from manufacturers including Mitsubishi and Panasonic.

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 can change throughout operation.

A heat pump may run relatively quietly when heating demand is low and operate at higher fan or compressor speeds when:

Outdoor temperatures are lower
The property requires more heat
Domestic hot water is being heated
The system is completing a defrost cycle

Manufacturers have also continued to develop quieter outdoor units. Mitsubishi Electric, for example, specifically promotes low operating noise across its Ecodan 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). A-weighting reflects the way the human ear responds to different sound frequencies.

When comparing heat pumps, you may come across two different measurements:

Sound Power Level

Sound power describes the total acoustic energy emitted by the heat pump itself.

It relates to the sound source rather than the position of the person listening, which makes sound power useful when comparing the acoustic performance of different heat pumps.

Sound Pressure Level

Sound pressure describes the sound level experienced or measured at a particular position.

This can be affected by:

Distance from the heat pump
Nearby walls and reflective surfaces
Buildings and solid barriers
Outdoor unit position
The location of neighbouring windows
The surrounding environment

This is why comparing a single decibel figure between two heat pumps does not necessarily tell you how loud either unit will sound once installed.

How Does MCS Assess Heat Pump Noise?

Heat pump noise is an important consideration when planning an installation, particularly where the outdoor unit is positioned near neighbouring properties.

Current MCS heat pump sound assessment guidance considers several factors rather than relying on a single manufacturer's noise figure.

The assessment uses factors including:

The manufacturer's A-weighted sound power level
Distance between the heat pump and the assessment position
The number of nearby reflecting surfaces
Solid barriers between the heat pump and the assessment position
The position of neighbouring windows and other relevant locations

This means outdoor unit positioning should be considered during the design stage rather than simply finding an available space after the equipment has been selected.

What Makes an Air Source Heat Pump Sound Louder?

Several factors can affect how noticeable an air source heat pump is.

Outdoor Unit Position

Location is one of the most important considerations.

A heat pump positioned directly beside a bedroom window or in a confined area surrounded by hard surfaces may be more noticeable than a unit installed in a suitable open location.

Nearby walls can also reflect sound rather than allowing it to disperse naturally.

Distance from the Heat Pump

Sound generally becomes less noticeable as the distance from the source increases.

The distance between the outdoor unit and neighbouring properties, bedrooms, patios and other frequently occupied areas should therefore be considered when planning the installation.

The Heat Pump Model

Different heat pumps have different acoustic characteristics.

Always check the manufacturer's technical information for the specific model rather than assuming every heat pump produces the same level of sound.

BPC Ventilation's air source heat pump range includes Mitsubishi and Panasonic units in different outputs and configurations.

Heating Demand

A heat pump does not necessarily operate at exactly the same output throughout the day.

Fan and compressor speeds can change according to:

Heating demand
Outdoor temperature
Required flow temperature
Domestic hot water demand
System controls

The amount and character of the sound can therefore change during normal operation.

Are Air Source Heat Pumps Louder in Cold Weather?

A heat pump 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 form on the outdoor heat exchanger.

Modern air source heat pumps manage this using an automatic defrost cycle.

During defrosting, the fan and compressor behaviour may temporarily change. You may also notice water draining beneath the unit or a temporary plume of water vapour.

This can be a completely normal part of winter heat pump operation.

Cold-weather performance should therefore be considered alongside noise when selecting and positioning an outdoor unit.

Can You Hear an Air Source Heat Pump Inside the House?

Whether an outdoor heat pump can be heard inside depends on several factors.

These include:

Distance from the building
Position relative to windows
Property construction
Outdoor unit mounting
Whether the unit is near a bedroom
The acoustic performance of the heat pump itself

Correct positioning can make a significant difference.

The outdoor unit should also be installed in accordance with the manufacturer's required airflow clearances.

Trying to hide a heat pump inside a small enclosure purely to reduce noise is not recommended unless the solution has been specifically designed around the manufacturer's requirements. Restricted airflow can negatively affect heat pump operation.

Can You Put a Heat Pump Behind a Fence or Screen?

A solid barrier can sometimes reduce the amount of sound reaching a particular position.

However, barriers and acoustic screens need to be planned carefully.

An air source heat pump relies on moving large volumes of air through the outdoor heat exchanger. A badly positioned fence or enclosure can restrict airflow and potentially reduce performance.

Any acoustic barrier should therefore maintain:

The manufacturer's required clearances
Unrestricted inlet airflow
Suitable discharge airflow
Access for servicing
Suitable drainage

Noise reduction should always be considered alongside correct heat pump operation.

How Can Heat Pump Noise Be Reduced?

Good product selection and system design are some 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 manufacturer-required airflow clearances
Avoiding unnecessarily enclosed locations
Considering nearby reflective walls
Using suitable anti-vibration mounting where required
Keeping the heat pump properly maintained

It is much easier to address these factors during the design stage than after the heat pump has already been installed.

Does Heat Pump Size Affect Noise?

Correct sizing is important for both heating performance and system operation.

A heat pump should ultimately be selected according to the calculated heating requirements of the property rather than simply choosing the largest available unit.

Factors including:

Property heat loss
Floor area
Insulation
Glazing
Required indoor temperatures
Local winter conditions
Heating flow temperature

all influence how much heat the property requires.

Correct system design helps ensure the selected heat pump can meet the heating demand without unnecessarily oversizing the equipment.

Do Underfloor Heating Systems Affect Heat Pump Noise?

The heating emitters inside the property can indirectly influence how a heat pump operates.

Underfloor heating is particularly well suited to air source heat pumps because it can provide useful room heat output using relatively low water temperatures when correctly designed.

Lower required flow temperatures can reduce how hard the heat pump needs to work compared with a system requiring much higher water temperatures.

A complete heating design should therefore consider the heat pump, underfloor heating or radiators, controls and required flow temperatures together.

Mitsubishi Ecodan Heat Pump Noise

Mitsubishi Electric has placed particular emphasis on acoustic performance within its Ecodan heat pump range.

For example, Mitsubishi has published a 45 dB(A) sound pressure level at one metre for certain Ultra Quiet Ecodan models.

However, this figure should not be applied to every Mitsubishi heat pump. Different outputs and models have different published sound data.

Always check the technical specification for the exact unit being considered.

BPC Ventilation currently supplies a range of Mitsubishi air source heat pumps alongside Panasonic equipment, cylinders, controls, buffer tanks and supporting heating components.

Choosing the Right Air Source Heat Pump

Noise is only one consideration when selecting an air source heat pump.

The system should also be selected according to:

Property heat loss
Required heat pump output
Low-temperature performance
Heating flow temperature
Radiator or underfloor heating requirements
Domestic hot water demand
Outdoor unit position
Available electrical supply
Acoustic performance

BPC Ventilation's heating team can provide support with heat pump selection and the supporting system components required for your property and project.

Air Source Heat Pump Support from BPC Ventilation

BPC Ventilation supplies air source heat pumps and supporting heating components for new builds, renovations and home heating upgrades.

The BPC heating team can help customers consider:

Suitable heat pump models
Required heat pump output
Outdoor unit positioning considerations
Underfloor heating products
Cylinders and buffer tanks
Heating controls
Compatible system components

BPC's current heating range includes products from established manufacturers including Mitsubishi and Panasonic.

Explore BPC Ventilation's heating solutions and heat pump support

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 the heat pump is depends on the model, its operating conditions, the distance from the listener and, importantly, where the outdoor unit is positioned.

Checking manufacturer sound data and considering noise during the heating-system design stage 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 heat pump installation that performs effectively without creating unnecessary noise.

Browse the BPC Ventilation air source heat pump range or speak to the heating team about your project.