Here in the UK, cooling has traditionally been associated with shops, gyms and offices rather than our own homes, so it is natural to ask, “Are air conditioning units noisy?” as more systems are added to bedrooms, living spaces and home offices. This guide explains what sort of sounds you can expect, how noise is measured, the regulations that apply in the UK, and how to keep your system running as quietly as possible in Bristol and across the South West.

Quick summary

Modern systems are designed to run quietly, especially on lower fan speeds and night modes.
Indoor units are typically similar to background household sounds when correctly specified and installed.
Outdoor sections are usually louder but can be positioned and mounted to minimise disturbance.
Unusual noises can indicate a fault and should be checked by a qualified, F-gas certified engineer.

How noisy are modern home AC units?

Noise is measured in decibels (dB), which is a logarithmic scale. A small change in the number can feel like a surprisingly big change to the ear. As a guide, a quiet room might be around 30 dB, normal conversation is roughly 60 dB, and heavy traffic can be much higher. Many modern indoor units for homes and small offices operate somewhere in the 20-40 dB range on their lower fan settings, which is closer to a quiet library or gentle background noise than to a busy street.

Outdoor sections, where the compressor is located, will usually sit higher up the scale. It is common to see manufacturer data sheets showing outdoor sound pressure levels around 50-60 dB, depending on the model and how hard it is working. That is closer to the sound of a dishwasher or a quiet street, and because the unit is outside, distance and building fabric help to reduce what you hear indoors.

Portable units and older systems can be noticeably louder because the compressor is inside the room, and the unit is not isolated from the floor in the same way as a wall-mounted system. If you are sensitive to sound or planning cooling for a bedroom, it is worth checking the published noise data and choosing equipment with a dedicated quiet or night mode.

UK regulations surrounding AC noise

Cooling at home can transform comfort, but it should not create a nuisance for neighbours. In the UK, local planning authorities assess noise impact from new plant such as outdoor sections, heat pumps and condensers. They often expect new equipment to be designed so the noise at the nearest noise-sensitive window is no more than a few decibels above, and in many cases a few decibels below, the existing background level at night.

To do this, consultants or installers may carry out a noise assessment following British Standards such as BS 4142. The assessment compares the predicted sound from the equipment with the local background, taking into account tonal or impulsive characteristics, and recommends mitigation where needed. Typical measures include acoustic enclosures, careful siting away from neighbouring windows, anti-vibration mounts and selecting quieter models.

If you live in a conservation area, listed building or dense terrace, the council may require a formal noise report to support an application. In these cases, working with an experienced installer who understands both planning and acoustic requirements is essential. For more details on what might be expected as part of an application, you can also review your local authority’s guidance alongside resources such as the Controlled Climate guide to planning permission for AC installations.

What actually makes the noise?

When a system is running normally, you should mainly notice a gentle whirring from the indoor fan and the sound of air moving through the room. At higher fan speeds, this becomes more noticeable, just as with any fan, but it should remain a steady, smooth sound rather than anything harsh or metallic.

The outdoor section will usually make a deeper hum as the compressor and outdoor fan operate. This can be more pronounced when the unit first starts or when it ramps up on a very hot day. However, you would typically hear it most clearly when standing near the unit outside, rather than inside the building, where walls and windows provide attenuation.

Other subtle sounds can be completely normal. You may occasionally hear a faint clicking from expansion and contraction of plastic casings, a gentle gurgling from refrigerant, or a slight change in tone as the system modulates to maintain the set temperature. These should be brief and not intrusive; anything sharp, repetitive or increasing in volume over time is a sign to have the system checked.

Normal sounds vs signs of a problem

A well-installed, well-maintained system should settle into a predictable pattern of sound. If something starts to change, the type of noise can give clues about what might be happening, although diagnosis and repair should always be left to qualified professionals.

Normal sounds often include:

A steady, smooth fan noise at different speeds.
Occasional quiet clicks as dampers or louvers move.
Soft gurgling as refrigerant flows, particularly at start-up or shut-down.

Potential warning sounds can include:

Rattling or vibration from loose fixings, brackets or pipework.
Banging, scraping or grinding noises from a fan or other moving parts.
Loud buzzing or humming that is new or increases over time.
Screeching, squealing or high-pitched tones.

If you notice any of these, it is sensible to switch the system off and contact a trained, F-gas certified engineer. Running a system that is making abnormal noises can risk further damage or, in a worst-case scenario, safety issues. An experienced engineer can safely inspect the equipment, check refrigerant levels, tighten fixings and replace worn components where necessary.

Installation quality, placement and building type

How noisy a system feels in day-to-day use is influenced not just by the model you choose, but also by how and where it is installed. A good design will consider room layout, neighbouring properties and local planning guidance, alongside comfort and efficiency.

Indoors, placing a wall unit directly above a bedhead or home-office chair can make you more aware of fan noise. Positioning it slightly to one side, using appropriate mounting brackets and ensuring pipework is properly clipped and insulated can all help to reduce perceived sound. In some homes, floor-mounted or ducted solutions may provide a quieter experience, especially where there are sloping ceilings or very low walls.

Outdoors, the aim is to give the unit enough free airflow and safe access for maintenance while avoiding positions that transmit vibration into the building or sit directly below a neighbour’s window. Mounting on a solid wall with anti-vibration pads, or on a ground frame in a courtyard, is usually preferable to thin walls or areas that might channel sound. In some cases, simple barriers such as fences or walls can also help to shield sound from nearby properties, as long as they do not restrict ventilation.

How to keep your system running quietly

Once your system is installed, day-to-day care plays a big part in keeping it operating smoothly and quietly. Many noise issues develop gradually as filters clog, fixings loosen, or outdoor units become obstructed by leaves and debris.

Simple steps that help include:

Cleaning or replacing indoor filters at the intervals recommended by the manufacturer.
Keeping outdoor sections clear of plant growth, leaves and other obstructions.
Checking that furniture has not been moved directly under or in front of indoor units.
Using quiet or night modes in bedrooms, especially in the evening.

In addition, regular professional servicing is strongly recommended. A planned visit allows an engineer to inspect fans, coils, brackets and pipework, check refrigerant charge, and identify anything that might develop into a noise problem later. If you prefer a structured approach, you can explore the servicing and maintenance options available so that checks are carried out at sensible intervals.

Bristol and South West context

In Bristol and across the South West, many homes are terraced, semi-detached or converted from older buildings. Streets can be narrow, and gardens small, which means outdoor sections may sit close to neighbours’ windows or shared boundaries. In these situations, quieter models, good mounting practice, and thoughtful placement become even more important.

Local experience also helps. Installers who regularly work in Bristol, Bath and surrounding towns will be familiar with the character of the housing stock, typical garden layouts and common planning conditions. At Controlled Climate’s Bristol service hub, we regularly design and install systems for noise-sensitive spaces such as bedrooms, home offices and treatment rooms, and can recommend approaches that suit compact plots and attached properties.

Questions to ask before you buy

If sound levels are a key factor for you, it is worth asking a few specific questions when you request quotes. This helps you compare options fairly and choose a setup that will feel comfortable for years to come.

What are the published indoor and outdoor noise levels in dB at different fan speeds?
Does the system include a night or quiet mode, and how does that affect performance?
Where is the outdoor section likely to be positioned, and how will vibration be controlled?
Has the installer considered local planning and any previous noise complaints in the area?
What maintenance is recommended to keep the system running quietly over time?

A reputable company should be happy to walk through these points with you and provide data sheets or further guidance. If you would like to research wider topics in your own time, the Controlled Climate guides library is a useful starting point.

FAQs: Noise from home AC units

Are indoor units loud at night?

On appropriate settings, most modern indoor units are quiet enough for use in bedrooms. Selecting a lower fan speed or a dedicated night mode usually keeps the sound to a gentle background level. If you are very sensitive to noise, mention this during your survey so the system can be sized and positioned with that in mind.

Will my neighbours hear my outdoor unit?

Neighbours may hear the outdoor section if it is installed very close to their property, particularly late at night when the general background noise is lower. Careful siting, appropriate mounting and, where required, a noise assessment help to reduce this risk. Your installer should also be able to explain how local planning guidance is taken into account.

Are portable air conditioners noisier than fixed systems?

Portable units are convenient and can be a good option for occasional use, but they tend to be louder than fixed systems because the compressor is inside the room. Fixed split systems separate the noisy components outside, which generally results in lower indoor noise levels for the same cooling effect.

Can maintenance really affect noise levels?

Yes. As filters become blocked and components gather dust, fans have to work harder, which can increase both noise and running costs. Loose panels or brackets may start to vibrate over time. Regular maintenance visits and simple user checks can prevent many of these issues. For structured guidance, you may find the dedicated maintenance tips guide helpful.

Who should install or repair a noisy system?

Installation, servicing and fault-finding should always be carried out by trained, F-gas certified engineers who are legally allowed to work with refrigerants. Working on pipework or the refrigerant circuit without the correct qualifications is unsafe and against UK regulations. If you are unsure who to contact, a good first step is to speak to a specialist company and ask about their engineers’ certifications.

Support from Controlled Climate

If you are concerned about noise or your existing system has started making unfamiliar sounds, it is safest to ask a qualified engineer for advice rather than trying to investigate internal components yourself. At Controlled Climate, our experienced, F-gas certified team designs, installs and maintains systems across Bristol and the wider South West, with particular care for noise-sensitive spaces such as bedrooms, studios and home offices.

If you would like a specialist to assess a noisy system, discuss quiet options for a new installation, or simply ask a few initial questions, you can get in touch with the team to arrange a survey or request advice.

Are Air Conditioning Units Noisy?