How quiet is air conditioning? Real figures, model by model
Very quiet indoors. The premium wall units from all four brands we fit go down to 19 dB(A) on their quietest setting. Below are the manufacturers' own figures, what quiet mode really does, how to keep a bedroom peaceful, and the 37 dB(A) limit that applies at a neighbour's window.
- quietest setting, premium 2.5 kW units
- 19 dB(A)
- limit at a neighbour's window
- 37 dB(A)
- typical 2.5 kW outdoor unit, cooling
- 46 dB(A)
- cut by Daikin's Silent button
- 3 dB(A)
Reading the numbers: dB(A), sound pressure and sound power
dB(A) is a decibel scale weighted to match how human ears hear. Spec sheets give two kinds of figure, and mixing them up causes most of the confusion online.
Sound pressure is roughly what you hear in the room, at the manufacturer's test position. It's the figure to compare when choosing a quiet unit. Sound power is the total noise the unit gives out, so it's always a bigger number. Daikin's 2.5 kW Perfera, for example, lists 41 dB(A) sound pressure on its top cooling speed but 54 dB(A) sound power. The planning noise calculation uses sound power.
Indoor sound levels, 2.5 kW wall units
Sound pressure in cooling, in dB(A), from each manufacturer's UK spec sheet or product page. High is each model's top fan speed.
| Model | Quietest | Low | High |
|---|---|---|---|
| Daikin Perfera (FTXM25A) | 19 | 25 | 41 |
| Mitsubishi Electric MSZ-LN25VG3 | 19 | 23 | 42 |
| Panasonic Etherea (KIT-Z25-CKE) | 19 | 25 | 39 |
| LG DUALCOOL Deluxe (DC09RH) | 19 | 27 | 42 |
| LG DUALCOOL Standard Plus (PC09SQ) | 19 | 27 | 41 |
| Panasonic TZ (KIT-TZ25-WKE) | 20 | 26 | 40 |
Checked October 2026. Manufacturers update models, so your quote names the exact model and we give you its sound data.
Bigger units are louder at their quietest
The same ranges at 3.5 kW and 5 kW. Look at the quietest column: a bigger unit can't turn down as far.
| Model | Size | Quietest | High |
|---|---|---|---|
| Daikin Perfera (FTXM35A) | 3.5 kW | 19 | 45 |
| Daikin Perfera (FTXM50A) | 5 kW | 27 | 46 |
| Mitsubishi Electric MSZ-LN35VG3 | 3.5 kW | 19 | 43 |
| Mitsubishi Electric MSZ-LN50VG3 | 5 kW | 27 | 46 |
| Panasonic Etherea (KIT-Z35-CKE) | 3.5 kW | 19 | 42 |
Sound pressure in cooling, dB(A), from the same manufacturer sources.
What quiet mode really does
Quiet mode runs the indoor fan at its lowest speed. That's the setting behind the 19 dB(A) headline figures. Panasonic labels it Q-Lo, quiet mode. Mitsubishi Electric's datasheet lists five speeds, from super low to super high. Daikin's Perfera has a Silent button on the remote that Daikin says lowers the indoor unit's sound by 3 dB(A), and a separate outdoor silent setting that lowers the outdoor unit by 3 dB(A).
The trade-off is airflow. Less air moving means less cooling or heating, so quiet mode works best once the room has reached temperature. Inverter units slow down by themselves as the room settles, so a correctly sized unit spends most of the night near its quietest anyway.
Keeping a bedroom quiet
How quiet a bedroom is depends as much on choices made at the install as on the brand.
- Choose a model with a low Low figure, not just a low quietest figure: that's the speed it spends most time at
- Don't oversize. A 5 kW unit can't turn down to 19 dB(A); a 2.5 kW unit can
- Cool the room before bed with the timer or app, then let it tick over in quiet mode
- Place the indoor unit so it doesn't blow straight onto the bed
- Fit the condensate drain with a proper fall, so water doesn't gurgle in the pipe
- Keep the filters clean, so the fan doesn't have to work harder
- Put the outdoor unit away from your own and your neighbours' bedroom windows where possible
Outdoor unit noise
The outdoor unit holds the compressor and the big fan, so it's louder than the indoor unit. Manufacturers' published sound pressure figures for 2.5 kW outdoor units are close: 46 dB(A) in cooling for Daikin's Perfera outdoor unit (RXM25A), Mitsubishi Electric's MUZ-LN25VG3 and Panasonic's Etherea outdoor unit. In heating, Daikin lists 47 dB(A) and Mitsubishi Electric 49 dB(A).
What your neighbours hear depends on distance, nearby walls that reflect sound, and anything solid in between. A unit tucked in a corner between two walls sounds louder than one on an open wall. We fit outdoor units on anti-vibration mounts and pick the position with neighbours' windows in mind.
The planning noise limit: 37 dB(A)
In England, a heating-capable unit on a house can be permitted development, with no planning application, only if it passes the MCS 020(a) sound calculation. The standard sets a limit of 37.0 dB(A) at every assessment position: 1 metre outside the centre of a door or window to a habitable room of a neighbouring property.
The calculation starts from the outdoor unit's sound power level, which is higher than its sound pressure. Mitsubishi Electric lists 60 dB(A) sound power for the MUZ-LN25VG3, for example. It then allows for distance, reflecting surfaces and any solid barrier. If a position fails, moving the unit or adding a barrier can fix it. Our planning permission guide covers the rest of the rules.
Noise questions
What is the quietest air conditioner in the UK?
Several premium wall units tie at 19 dB(A) on their quietest setting, including Daikin's Perfera, Mitsubishi Electric's MSZ-LN, Panasonic's Etherea and LG's DUALCOOL Deluxe at 2.5 kW. The differences show at normal speeds. On low, the MSZ-LN25 lists 23 dB(A) against 25 to 27 dB(A) for the others.
Is air conditioning too noisy to sleep with?
Not usually. A correctly sized 2.5 kW premium unit on quiet mode runs at about 19 to 20 dB(A), according to the manufacturers. Problems usually come from an oversized unit, a unit blowing straight at the bed, or a gurgling drain, all of which a good install avoids.
Will my neighbours hear the outdoor unit?
They may hear it close up, but the planning rules limit what reaches their windows. For permitted development, the MCS 020(a) calculation must show 37 dB(A) or less 1 metre outside each neighbouring habitable-room door or window. We check this at the survey.
Is Daikin or Mitsubishi Electric quieter?
They're very close. At 2.5 kW both list 19 dB(A) on the quietest setting and 46 dB(A) for the outdoor unit in cooling. Mitsubishi Electric's MSZ-LN25 is a little quieter on low (23 against 25 dB(A)), and Daikin's Perfera a little quieter on high (41 against 42 dB(A)).
Why is my air conditioning louder than it used to be?
Clogged filters, a dirty fan or coil, a loose panel or a worn fan motor are the usual causes. Clean the filters first. If it's still noisy, or it's rattling or grinding, book a repair visit so an engineer can find the cause.