At 7 kW, the quietest split system we install is 10 decibels quieter on its energy label than the cheapest to run. That's half as loud, for $37 a year more. Here's the quietest at every size, why brochures print a lower number, and the NSW hours for your neighbours.
The noise figure on the energy label
The energy rating label on a split system shows two noise figures: one for the indoor unit and one for the outdoor unit. They're in decibels, written dB(A). Lower is quieter.
Mitsubishi Electric's split systems brochure explains what they are. Each one is the unit's sound power level, measured while it cools at the standard's test point: 35°C outside and 27°C inside. In other words, it's how much noise the unit makes when it's working hard on a hot afternoon.
Every unit is measured at the same test point, so the label is the figure to compare from one brand to the next.
Why the brochure says 21 dB
Brochures often print a much lower number. Mitsubishi Electric's MSZ-EF flyer says "Quiet 21dB" for its 2.5 and 3.5 kW models. The energy label of the MSZ-EF 3.5 kW says 53.
Both are right. The flyer's figure is a sound pressure level: what you'd measure at some distance from the unit, here on its Quiet fan speed. The flyer's own spec table gives 21 dB(A) on Quiet up to 42 on the top fan speed, cooling.
The NSW EPA explains the difference with a light bulb. Sound power is like the bulb's wattage: it's the same wherever you stand. Sound pressure is like how bright the bulb looks, which depends on how far away you are.
The same flyer prints both for the outdoor unit: 49 dB(A) sound pressure and 62 sound power. So compare a label with a label, and never a label with a brochure.
How much quieter is quieter
Decibels don't add up like ordinary numbers. The NSW EPA's noise guide gives these rules of thumb for a steady sound:
- 2 dB or less: you usually won't notice it
- 3 dB: just noticeable
- 5 dB: clearly noticeable
- 10 dB: twice as loud, or half as loud
- 20 dB: much louder or quieter
So 1 dB between two labels makes no real difference. 10 dB is the difference between one unit and another twice as loud.
The quietest split system at each size
Here's the quietest indoor unit we install at each size, by its energy label, next to the loudest at the same size. The sizes are the ones on our size pages.
| Size | Quietest indoor unit | Label | Loudest indoor unit | Label |
|---|---|---|---|---|
| 2.5 kW | MHI Avanti | 53 dB | Fujitsu Comfort, Hisense J-Series and LG DUALCOOL AI | 59 dB |
| 3.5 kW | Mitsubishi Electric MSZ‑EF | 53 dB | Panasonic Z Series | 60 dB |
| 5 kW | Mitsubishi Electric MSZ‑EF | 55.2 dB | LG DUALCOOL AI 4.8 kW and Hisense J-Series 5.3 kW | 62 dB |
| 7 kW | MHI Bronte 7.1 kW | 55 dB | Seven models, the Daikin Alira X 7.1 kW among them | 65 dB |
| 8 kW | MHI Bronte | 58 dB | LG DUALCOOL AI 8.5 kW | 69 dB |
At the bedroom sizes the gap is 6 to 7 dB, which you'd clearly notice. At 7 and 8 kW it's 10 to 11 dB, so the loudest is about twice as loud as the quietest.
Four models have no noise figure in the government's data: the Panasonic RZ at 2.5, 3.5 and 8 kW, and the Rinnai T Series at 8 kW. We've left them out rather than guess.
Quiet or cheap to run
The quietest unit isn't always the cheapest to run. Here are both at each size. The cost is a year of cooling and heating for Sydney's climate zone, at 31.79 cents a kWh.
| Size | Cheapest to run | Label | Quietest | Label | The quietest costs more a year |
|---|---|---|---|---|---|
| 2.5 kW | ActronAir Serene 2.6 kW, $128 | 56.6 dB | MHI Avanti, $171 | 53 dB | $43 |
| 3.5 kW | Daikin Alira X, $189 | 58 dB | Mitsubishi Electric MSZ‑EF, $258 | 53 dB | $69 |
| 5 kW | Daikin Alira X, $298 | 61 dB | Mitsubishi Electric MSZ‑EF, $397 | 55.2 dB | $99 |
| 7 kW | Daikin Alira X 7.1 kW, $464 | 65 dB | MHI Bronte 7.1 kW, $501 | 55 dB | $37 |
| 8 kW | Rinnai PB Series, $543 | 64.6 dB | MHI Bronte, $580 | 58 dB | $37 |
The trade is clearest at 7 kW. The MHI Bronte 7.1 kW is 10 dB quieter than the Daikin Alira X 7.1 kW, half as loud by the EPA's rule of thumb, and costs $37 a year more to run.
At 5 kW the quietest costs $99 a year more for a 6 dB gap. You don't have to pick an end. At 3.5 kW the Mitsubishi Electric MSZ-LN is 55 dB, 2 dB off the quietest, and costs $219 a year: $39 less than the quietest.
The outdoor unit and your neighbours
The outdoor unit has its own figure on the label, and it's the one your neighbours hear. It isn't always the same brand that's quietest inside:
| Size | Quietest outdoor unit | Label | Loudest outdoor unit | Label |
|---|---|---|---|---|
| 2.5 kW | Fujitsu Lifestyle and Mitsubishi Electric MSZ‑EF | 55 dB | ActronAir Serene 2.6 kW | 63.7 dB |
| 3.5 kW | Mitsubishi Electric MSZ‑LN and LG DUALCOOL AI | 58 dB | Fujitsu Comfort 3.4 kW | 65 dB |
| 5 kW | Daikin Alira X, Cora, Lite and Zena, and Fujitsu Lifestyle | 59 dB | Daikin Skywall | 68 dB |
| 7 kW | LG DUALCOOL AI 7.1 kW | 63 dB | Panasonic RZ and Z Series, Samsung Aero and WindFree 6.8 kW | 68 dB |
| 8 kW | LG DUALCOOL AI 8.5 kW | 64.7 dB | Daikin Skywall 8.5 kW | 71 dB |
In NSW there are set hours when your air con shouldn't be heard inside a neighbour's home. Under the rules the EPA updated on 31 August 2026, they are:
- weekdays: before 7 am and after 11 pm
- weekends and public holidays: before 8 am and after 11 pm
That counts any room of their home except a garage, storage area, bathroom, laundry, toilet or pantry. The hours don't apply while a Bureau of Meteorology severe or extreme heatwave warning is in force for your area.
Council or the police can give a warning. A fine of $400 can follow if the noise goes on in the 40 days after it. The EPA's advice is to choose a quiet model, and to place the outdoor unit away from your neighbours' bedroom and living room windows, or shield it.
Choosing a quiet one
Each of our size pages lists every model at that size with its label noise and its running cost, so you can see both at once. Start with the 3.5 kW page for a main bedroom, or go up or down from there.
Where the outdoor unit goes matters as much as which one you buy. When you ask for a quote, add a photo of the spot you have in mind for it. Stand a few metres back, so the ground, the wall behind it and any fence or window nearby are all in the frame.
Sources
- GEMS registered air conditioners dataset (E3 program), data.gov.au, CC BY 3.0: the indoor and outdoor noise figures on each model's energy label, and its yearly cooling and heating energy for Sydney's climate zone, from our own sync of 1 September 2026.
- Energy Made Easy, the AER's plan data: the median usage rate across 170 Ausgrid plans, September 2026, with GST added: 31.79 cents a kWh.
- Mitsubishi Electric split systems brochure 2025, on our manuals and brochures page: the label's noise figures are sound power levels, measured cooling at 35°C outside and 27°C inside (conditions T1 of AS/NZS 3823.1.1).
- Mitsubishi Electric MSZ-EF flyer, on our manuals and brochures page: "Quiet 21dB", the indoor sound pressure from 21 to 42 dB(A) cooling, and the outdoor unit's 49 dB(A) sound pressure and 62 sound power, for the MSZ-EF35.
- NSW EPA, Noise Guide for Local Government (2023): sound power against sound pressure, the light bulb, and how changes of 2 to 20 dB sound.
- NSW EPA, Preventing neighbourhood noise: updated 31 August 2026. The hours for air conditioners, the heatwave exception, which rooms count, the $400 fine and the advice on placement.
- Our split catalogue on 15 October 2026: 105 models in the five size bands, the quietest, loudest and cheapest to run at each size.
