How Loud are Heat Pumps and will it disturb my neighbours?

The good news is that modern ASHPs are significantly quieter than older models, and regulations are in place to manage noise levels.

What does an ASHP sound like?

Generally, an ASHP produces a low hum or whirring sound.

It's primarily from:

• The fan: Moving air over the coil

• The compressor: The main mechanical component that compresses the refrigerant

Think of it as being similar to:

• A modern refrigerator or freezer (often around 30-50 dB)

• A dishwasher (40-60 dB)

• The outdoor unit of an air conditioning system

Typical Noise Levels (in Decibels - dB):

• Most modern ASHPs operate in the range of 40 to 60 dB (measured at the unit itself)

• Many leading brands are designed to be at the lower end of this scale, often around 40-50 dB. Some can even go as low as 35-38 dB in certain modes

How loud is that in context?

• 30 dB: Whispering

• 40 dB: Quiet library, a running laptop

• 50 dB: Quiet conversation, inside a quiet office, a typical refrigerator

• 60 dB: Normal conversation

• 70 dB: Washing machine, vacuum cleaner, typical street traffic

So, while you might hear a low hum if you're standing right next to the outdoor unit, it's generally designed to blend into background noise.

Will it disturb you?

• Proximity: If the unit is installed directly outside a bedroom window, you might notice it, especially at night when background noise is lower.

• Location: ASHPs are installed outside. Unless you have poor sound insulation in your walls/windows, you're unlikely to hear it significantly inside your home, especially compared to the noise of an old boiler.

• Defrost Cycle: In cold weather, the unit will periodically go into a defrost cycle (to melt ice buildup). During this, it might make a slightly louder "whooshing" or "gurgling" sound for a few minutes. This is normal but can be more noticeable.

• Colder Weather: The heat pump works harder in colder temperatures, which can sometimes lead to a slightly increased noise level, but generally still within acceptable limits.

Will it disturb your neighbours (and regulations in Scotland)?

This is where planning and noise regulations come into play.

• Permitted Development (UK wide, including Scotland): For an ASHP to be considered "permitted development" (meaning you generally don't need full planning permission), it must meet certain criteria, including noise limits.

• Noise Limit: The key regulation (MCS 020 standard) states that the sound pressure level from the ASHP must not exceed 42 dB(A) when measured at a point one metre from your neighbour's nearest habitable room window or door. A "habitable room" includes living rooms, bedrooms, dining rooms, but generally not bathrooms, WCs, or kitchens.

• MCS-Certified Installers: A reputable MCS-certified installer will perform a noise assessment during their survey. They will calculate the expected noise level at your neighbours' properties based on the heat pump's specifications, its distance from boundaries, and any potential sound reflections (e.g. from walls). They are legally obliged to ensure the installation complies with these noise limits.

Mitigation

If the calculations show it might exceed the limit, the installer will recommend mitigation measures, such as:

• Strategic Placement: Positioning the unit further from a neighbour's property or away from their main windows.

• Anti-vibration Mounts: Using rubber feet or pads to prevent vibrations from transferring to the ground or wall.

• Acoustic Barriers: In some cases, a fence, wall, or even dense planting can help absorb or block sound.

• Enclosures: Rarely, a purpose-built acoustic enclosure might be used, but this can impact airflow and should only be designed by experts.

• Quiet Mode: Some heat pumps have a "quiet mode" that reduces fan speed (and thus noise) during sensitive times (e.g. at night), though this might slightly reduce output.

In more densely populated areas or terraced housing, the careful placement and noise assessment become more critical.

Recommendations

• Discuss noise with your installer: When getting quotes, specifically ask about the decibel levels of the proposed models.

• Ask for a noise assessment: Ensure the installer includes a noise assessment as part of their site survey and explains how they will meet regulatory requirements.

• Consider placement: Think about where the unit will go and its proximity to your own and your neighbours' most used rooms or outdoor spaces.

• Modern models are key: Stick to reputable brands and newer models, as they have significantly invested in quieter operation.

In most well-planned installations, modern ASHPs should not cause an intrusive noise disturbance to you or your neighbours in.