Air Conditioning Noise Levels UK: Regulations and Quiet Models

How loud is air conditioning?

Modern air conditioning is much quieter than most people expect. The indoor unit, the part on your wall, is the quietest, running at around 19 to 23 decibels on its lowest setting, which is close to a whisper. The outdoor unit is the one you might notice, and it typically sits around 45 to 55 decibels at a metre away, similar to a quiet conversation. From inside the house, or from next door, you hear far less than that.

The units we fit are Toshiba, which are among the quieter systems on the market, and getting the installation right matters just as much as the unit itself.

Indoor noise: will it keep you awake?

For a bedroom, the indoor unit is not something that will disturb your sleep. On its night setting the fan slows right down and the unit runs at its quietest, which is why air conditioning works well in bedrooms and nurseries. On higher fan speeds it is louder, but that is the setting you would use to cool a room quickly rather than to run overnight.

Toshiba's Shorai units in particular are built for quiet running, so if a bedroom is your main concern it is worth choosing one of those.

Outdoor noise and your neighbours

The outdoor unit is the part worth thinking about, because it is outside and closer to boundaries. A well-chosen, correctly sized unit that is sited sensibly is rarely a problem, but a poorly placed one can be. The things that keep it quiet are:

The right size: an oversized unit runs harder than it needs to. A correctly sized one runs slower and quieter.

Good positioning: away from your own and your neighbour's windows, and not boxed into a tight corner where sound reflects.

Anti-vibration mounts: these stop the low hum travelling into the wall or the ground.

Distance from the boundary: more distance means less noise reaching next door.

Noise and planning rules

Noise is part of the planning picture too. The permitted development rules for outdoor units include a condition that the unit is sited to keep noise down, and installers assess the likely noise reaching the nearest neighbour as part of showing the installation is acceptable. This is one reason positioning is decided carefully at the survey rather than on the day. If a unit cannot be sited to meet the conditions, that is something we would raise with you before booking.

Separately, statutory nuisance rules apply to every household, so a system that genuinely disturbs a neighbour could be a problem regardless of planning. Sensible siting avoids this, and it is exactly what the survey is for.

How we keep installations quiet

Our approach is straightforward: size the unit correctly for the room, choose a quiet Toshiba unit, and take time over where the outdoor unit goes. We use anti-vibration mounts as standard and position units with your neighbours in mind. If you have a preference about where the outdoor unit sits, tell us on the survey and we will work with it where we can.

A few things you can do

Talk to your neighbours before the install if the unit will sit near a shared boundary. Most people are fine once they know what to expect.

Avoid siting the unit directly outside a bedroom window, yours or theirs.

Use the timer so the system is not running through the quietest hours unless you need it.

If quiet running is a priority for you, request a quote and we will recommend the right unit and the best position on the survey. You may also find our guide to planning permission and our loft conversion guide useful.

Air conditioning noise: common questions

Will the indoor unit keep me awake at night?

No. On its night setting it runs at close to a whisper, which is why air conditioning suits bedrooms well.

Could the outdoor unit annoy my neighbours?

It is unlikely with a correctly sized unit that is sited well and fitted on anti-vibration mounts. We plan the position with neighbours in mind.

Are there legal limits on air conditioning noise?

Planning rules include a noise condition for outdoor units, and statutory nuisance rules apply to everyone. We site units to comply with both.

Which is the quietest position for the outdoor unit?

It depends on your property, but generally away from windows, not enclosed in a tight space, and as far from boundaries as is practical. We advise on this at the survey.