From 19 dB(A) Indoor and outdoor figures compared
The Quietest Air Conditioning, Measured in Decibels
The quietest air conditioning for a UK home is a wall-mounted split system, and the best indoor units are listed at 19 dB(A) on their lowest fan speed. This guide compares six models using manufacturer data. Aircova fits quiet units across London and the South East, with a fixed price before any work starts.
- Figures from UK spec sheets
- Outdoor noise checked at survey
- F-Gas certified engineers
Last updated: October 2026. Prices last checked: October 2026
The short answer
Which is the quietest air conditioning for a UK home?
The quietest home air conditioning is a wall-mounted split with an indoor unit rated at 19 dB(A) on its lowest fan speed. Daikin, Mitsubishi Electric, Fujitsu, Toshiba and Panasonic all list a 2.5kW model at that level. Aircova fits all five, and outdoor units run at about 44 to 46 dB(A).
Every figure for these quiet air conditioning units comes from the manufacturer’s UK spec sheet or product table. Indoor figures are sound pressure at the lowest fan speed in cooling. Outdoor figures are nominal cooling sound pressure. All are 2.5kW models, the usual size for a bedroom.
| Model | Lowest setting | Indoor dB(A) | Outdoor dB(A) |
|---|---|---|---|
| Toshiba Haori RAS-B10N4KVRG-E with RAS-10J2AVSG-E1 | Quiet | 19 | 44 |
| Daikin Perfera FTXM25A with RXM25A | Silent operation | 19 | 46 |
| Mitsubishi Electric MSZ-LN25VG3 with MUZ-LN25VG3 | Super low (SLo) | 19 | 46 |
| Fujitsu (GENERAL) ASEH09KGTG with AOEH09KGCG | Quiet | 19 | 46 |
| Panasonic Etherea CS-Z25CKEW with CU-Z25CKE | Quiet low | 19 | 46 |
| Fujitsu (GENERAL) ASEH09KMCG with its outdoor unit | Quiet | 20 | 46 |
Sources: Daikin UK product tables for FTXM-A and RXM-A, the Mitsubishi Electric UK MSZ-LN specification sheet (February 2026), GENERAL UK product pages for the Fujitsu ranges, the Toshiba UK Haori engineering data book and the Panasonic UK Etherea product page. Checked October 2026.
Five indoor units tie at 19 dB(A), so the real gaps show up outdoors and at higher fan speeds. On full fan, the same units run at 39 to 42 dB(A).
The Daikin Perfera product page quotes its quiet operation down to 19 dB(A) sound pressure. Toshiba says the Haori outdoor unit has a silent mode down to 39 dB(A), which is useful where the condenser sits near a bedroom window.
One detail catches people out. Panasonic lists the same Etherea indoor unit at 21 dB(A) when it is sold for multi-split use. Always check the figure for the exact pairing you are quoted.
Choosing by brand? See how we fit Daikin air conditioning, Mitsubishi Electric units and Fujitsu air conditioning. In the UK, Fujitsu’s home range is now sold under the GENERAL name.
Decibels explained
What does 19 to 21 dB(A) actually sound like?
At 19 to 21 dB(A), most people hear a soft rush of air, quieter than a whisper. In a quiet bedroom at night, you may need to stand close to the unit to hear it at all.
The decibel scale is logarithmic. A rise of 10 dB sounds roughly twice as loud, so 29 dB(A) seems about twice as loud as 19 dB(A).
The “A” in dB(A) means the reading is weighted to match human hearing, so look for dB(A) on any spec sheet.
Useful reference points
- 19 to 21 dB(A): a wall unit on its lowest fan speed
- About 30 dB(A): the World Health Organization night guideline for bedrooms
- 39 to 42 dB(A): the same indoor units on full fan
- 44 to 46 dB(A): an outdoor unit cooling at its rated output
Traffic on a busy London street or a running boiler is often louder than a unit on low fan, so you will not pick the unit out.
On a hot afternoon the unit speeds up to pull the room down, then slows at the set point. A well sized unit spends most of the night on low fan.
Reading a spec sheet
Sound pressure vs sound power: which number to trust
Spec sheets list two kinds of noise figure, and they are not the same thing. Mixing them up is the most common reason quiet air conditioning units look louder or quieter than they are.
Sound pressure, Lp
- What it is
- The noise you hear at a set point near the unit in test conditions.
- Changes with
- Distance, the room and the fan speed.
- Use it for
- Comparing how loud indoor units feel in a room.
- Example
- Daikin Perfera 2.5kW: 19 dB(A) on silent operation.
Sound power, Lw
- What it is
- The total sound energy the unit gives off.
- Changes with
- Nothing outside the unit. It is fixed for the model.
- Use it for
- Noise calculations for neighbours and planning.
- Example
- Same Perfera indoor unit: 54 dB(A) in cooling.
Sound power is always the bigger number, because it describes the source rather than what reaches your ear. A brand quoting 19 dB(A) and another quoting 54 dB(A) may be describing equally quiet units.
The Mitsubishi Electric MSZ-LN specification sheet shows both. The MSZ-LN25VG3 indoor unit runs from 19 to 42 dB(A) sound pressure across its five cooling fan speeds, with a sound power of 58 dB(A). The MUZ-LN25VG3 outdoor unit is 46 dB(A) sound pressure in cooling and 60 dB(A) sound power.
Indoor vs outdoor figures
The indoor unit is a fan and a coil, so it can run almost silently. The outdoor unit holds the compressor and a larger fan, so it is always louder. Heating mode often adds a few decibels outside: the Toshiba Haori outdoor unit is 44 dB(A) cooling and 46 dB(A) heating.
An inverter compressor slows down rather than switching off, so the outdoor unit settles at a lower, steadier level once the room is at temperature.
Portable units
Why portable air conditioners are so much louder
A portable puts every noisy part in the room with you. The compressor, the condenser fan and the indoor fan all sit inside one box on the floor.
A split system moves the compressor outside, behind a wall. Only the indoor fan is left in the room, and that is why the gap in noise is so large.
The hot air hose through an open window lets street noise in as well.
Our guide to portable vs split air conditioning compares cost, cooling power and noise side by side.
Installation
How installation makes a quiet unit quieter
A 19 dB(A) indoor unit can still be annoying if it is fitted badly. The way it is sized, placed and mounted matters as much as the model.
- Size it right. A 2.5kW unit in a 3.5kW room runs flat out for hours, so check the size with a heat load or our BTU calculator.
- Place the indoor unit well. Keep it off the wall behind your bed and aim airflow away from where you sit.
- Site the outdoor unit away from windows. Avoid bedroom windows, yours and the neighbours’, and avoid corners that bounce sound back.
- Use anti-vibration mounts. Rubber isolators, or a ground pad instead of a thin wall, stop the compressor humming through the brickwork.
- Fix the condensate drain properly. A drain with the right fall stops gurgling and dripping sounds at night.
- Commission with care. A correct refrigerant charge and vacuum test stop the hissing and strain an overcharged system can make.
Every wall-mounted air conditioning job we do includes these checks, and the outdoor position is agreed with you first.
If you want to cool the bedroom first, our bedroom air conditioning page covers sizes, placement over the bed and fitted prices. A single 2.5kW unit is fitted from £2,195, or from £2,395 for Daikin and Mitsubishi Electric.
For several rooms, a multi-split system uses one outdoor unit instead of several. Yearly air conditioning servicing keeps fans clean and balanced, so units stay near their rated noise.
Neighbours and planning
Outdoor unit noise, neighbours and MCS 020
Neighbours never hear the indoor unit, so noise rules apply to the condenser outside.
In England, an air source heat pump can often go in under permitted development. The rules changed in May 2025 through the 2025 permitted development amendment order. One condition is that the unit is not used solely for cooling, so a split that heats and cools is treated differently from a cooling-only unit.
What MCS 020 checks
The same rules require the install to meet MCS 020 a), a sound calculation for permitted development. It became mandatory on 20 September 2025.
The calculation starts with the outdoor unit’s sound power level. It then allows for distance and any solid barrier between the unit and the nearest neighbour’s habitable room window or door. The predicted level one metre from that window must not go above 37 dB(A) under MCS 020 a). The older MCS 020 used 42 dB(A), so you may still see that figure quoted.
- A quieter outdoor unit gives more room to place it
- Distance from the neighbour’s window cuts the predicted level
- A solid wall or fence that blocks the line of sight helps
- A hard corner or a spot between two walls adds noise
Flats, listed buildings and conservation areas often need consent whatever the noise figures say. Our guide to air conditioning planning permission explains the rules in more detail. Always check with your council before you book.
In flats, the freeholder usually has to agree too. See air conditioning for flats.
We run the noise check at the survey and choose a position that passes it. Our air conditioning installation price includes that work. To see what your rooms would cost, get an instant quote or read our air conditioning cost guide.
FAQs
Quiet air conditioning questions
What is the quietest air conditioning unit in the UK?
Several wall-mounted splits share the top spot at 19 dB(A) indoors on their lowest fan speed. The Daikin Perfera, Mitsubishi Electric MSZ-LN, Fujitsu KG, Toshiba Haori and Panasonic Etherea all list a 2.5kW model at that level. Outdoors, the Toshiba Haori is lowest in our table at 44 dB(A) in cooling. The others sit at 46 dB(A).
Is 19 dB(A) quiet enough to sleep?
Yes, for nearly everyone. 19 dB(A) is quieter than a whisper and well below the 30 dB(A) the World Health Organization suggests for bedrooms at night. Most rooms have more background noise than that from traffic or the house itself. The figure applies on the lowest fan speed.
What is the difference between dB and dB(A)?
dB(A) is a decibel reading weighted to match human hearing. Plain dB treats all frequencies equally, while dB(A) gives less weight to very low and very high tones that we hear less well. Manufacturers quote air conditioning noise in dB(A), so it is the fairest number to compare between brands.
Why does my air conditioner seem louder than the spec sheet says?
Usually because it is not running on its lowest fan speed. Spec sheet minimums apply to quiet or night mode, and a unit pulling a hot room down on full fan runs at 39 to 42 dB(A). Other causes are an undersized unit working flat out, dirty filters, a loose panel or a bracket passing vibration into the wall.
Are ducted systems quieter than wall-mounted units?
They can be, because the indoor unit sits in the loft or ceiling void, away from the room. You hear air moving through the grilles rather than a fan on the wall. It also costs more, from £6,995 for two to three rooms.
Is a multi-split outdoor unit louder than a single one?
A multi-split outdoor unit is larger, as it serves several rooms, so its sound figures are often higher than a 2.5kW single unit. Even so, one larger condenser can be quieter overall than two or three small ones on the same wall. We check the exact model’s sound power in the noise calculation at survey.
Can I make an existing air conditioner quieter?
Often, yes. Clean or replace the filters, check the indoor panel is clipped in, and make sure nothing touches the outdoor fan. Fitting anti-vibration mounts under the outdoor unit can cut humming through the wall. If a rattle or grinding noise remains, the fan or compressor may need attention from an F gas engineer.
Does a quiet outdoor unit avoid the need for planning permission?
Not on its own. A quiet unit makes it easier to pass the MCS 020 a) sound check used for permitted development in England, but other conditions apply too. Units used only for cooling, flats, listed buildings and conservation areas can need consent. Check with your council before work starts.
Get your fixed price
Tell us which rooms you want to cool and where the outdoor unit could go. We will suggest a quiet model, check the noise rules and send you a fixed price. No pressure and no obligation.
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