How noisy are Air Conditioning units?

The noise level of modern air conditioning units in the UK can vary depending on a number of factors, such as the type of unit concerned, its size and the location where it is installed.

Some modern indoor air conditioning units are designed to operate quietly, with noise levels typically around 19-20 decibels (dB) at low speed. This is about the same level of noise as a whisper or a quiet library. Modern outdoor units are, depending on the size and the manufacturer, typically around the 50dba mark, though its important to remember that rating is when the unit is running at maximum capacity and is measured one metre in front of the unit; the reality is the unit will hardly ever run at maximum capacity and nor will any person be standing in one metre in front of said unit.

However, if the air conditioning unit is not installed properly or is too small for the space it is intended to cool, it may have to work harder to achieve the desired temperature, resulting in increased noise levels. Additionally, older or poorly maintained air conditioning units may also be noisier than newer models. 

New models have compressors which use inverter technology and these are really very quiet; if your unit doesn't have inverter technology then you should consider replacing it, if not for the energy efficiency savings then for the lower noise levels!

It's also worth noting that noise tolerance can vary greatly among individuals, so what one person finds noisy may not be a problem for another. 

If you're concerned about noise levels, it's always a good idea to ask your air conditioning installer or supplier for information on the noise level of the specific unit you're considering, and to seek professional advice on the best installation and maintenance practices to minimise noise.