Are mini splits quiet, inside and outside?
Indoors, very: MRCOOL's DIY 5th Gen 12k lists 18 dB(A) on its silent speed. Outdoors is another matter, with figures from 46 to 63 dB(A) among the units listed here.
Every mini-split checked publishes both kinds of figure. The indoor one usually comes per fan speed; MRCOOL, for example, lists the DIY 5th Gen 12k at 43, 39.5, 33.5, 24 and 18 dB(A), from Turbo down to Si, its silent speed. Our MRCOOL mini-split decibels page lists every current MRCOOL line, including the contractor-installed Olympus E Star, whose 24k head lists 16 dB(A) on Si. The low end is what runs overnight once the room is at temperature, and the top end is what you hear while the unit works hard. The bedroom section below groups those lowest figures by the mode each maker states.
The outdoor figure is usually a single number, and it is what reaches the patio and the neighbors. It ranged from 46 dB(A) for Fujitsu's premium Altair 500 to 63 dB(A) for Klimaire's biggest DIY unit.
Daikin, which a contractor quotes and installs and which is not among the picks here, prints both kinds too. Our Daikin mini-split decibels page lists indoor dB(A) at each fan speed in cooling and heating, with wall units from 19 dB(A) on SL, its quiet setting, and outdoor units from 47 dB(A) in cooling.
A unit can be quiet on one side and not the other. Klimaire's DIY kit has the lowest outdoor figure of the DIY kits, 50 dB(A), yet its quietest indoor figure is 30 dB(A); MRCOOL's kits reach 18 dB(A) indoors and 54 dB(A) or more outside. Decide which side your home cares about more.
For a living room, where the head runs on low, medium or high with the TV on rather than on silent, our living room mini-split guide reads 18,000 and 24,000 BTU heads at those speeds and weighs the outdoor unit by the patio. A ducted whole-house system is covered in our guide to central air conditioners and heat pumps, which compares outdoor condensers that publish AHRI 270 sound ratings. And for a condo, addition or garage office that already has a sleeve about 42 inches wide under the window, the quietest PTAC units compares packaged units that cool and heat from one chassis.
Only Fujitsu says how it measures
Fujitsu's figures come from its anechoic chamber, a room built to absorb echoes, and the company warns that "the sound levels measured in actual installation conditions might be higher than the specified values here." Our Fujitsu mini-split decibels page adds the microphone positions from Fujitsu's design manuals and lists every current AIRSTAGE unit by named fan speed.
Mitsubishi's submittals are silent on method. Its service manuals are not, and our Mitsubishi mini-split decibels page quotes their anechoic-room note and lists every current M-Series figure.
Klimaire states only that its indoor figures are measured in cooling mode. MRCOOL, Senville, Pioneer, Bosch and ACiQ give no distance, standard or mode at all. A 17.5 from one brand and an 18 from another are, for practical purposes, the same number, and a head rated without stated test conditions cannot be lined up against a rival brand's, as comparing decibel ratings shows.
Some labels are unclear too. Senville prints five indoor figures for its LETO under a header naming only four speeds, Turbo, H, M and L, which leaves the speed behind its 17.5 dB unknown. Our Senville mini split noise level page lists every current Senville figure by size and fan speed.
Can you install a mini split yourself?
Yes, with a pre-charged kit, but read the warranty first. Pre-charged "quick connect" kits let a handy homeowner join the lines without vacuum pumps or refrigerant gauges, and after noise, the warranty terms are the biggest decision here.
| Warranty stance | Makers |
|---|
| DIY allowed | MRCOOL, Klimaire |
| DIY allowed, parts only | Della (registered installs) |
| Licensed or qualified contractor required | Senville, Bosch, ACiQ, Mitsubishi |
MRCOOL's warranty applies to systems installed according to its installation instructions, though it notes a licensed contractor may be necessary where the law requires one. Klimaire allows DIY installation if you follow local code and gives full cover if you register within 45 days. Senville's warranty is valid only if a licensed professional installs the unit.
Pioneer's Essenza uses a standard flare line set that has to be evacuated. Whatever its warranty says, it is not a plug-together kit.
Quiet installation starts with the base
Put the outdoor unit where its noise will not disturb others, on a base that will not vibrate, and hang the indoor unit on a solid wall.
Neighbors come first in the manuals. MRCOOL says not to install the outdoor unit where its noise will disturb others, and Pioneer asks for a spot where the discharge air and operating sound will not.
The base comes next. MRCOOL's checklist wants a location that is firm and solid and will not vibrate, with rubber gaskets on wall brackets where allowed. If the system could pass vibration into a structure, Pioneer calls for rubber vibration absorbers. Della suggests rubber foot pads, and Klimaire sells a rubber vibration pad set.
Do not cut the line set too short
A minimum pipe run of 9.84 ft is needed to minimize vibration and excessive noise, according to Senville's LETO manual.
Indoors, Pioneer's rule is simple: no wall that is subject to vibration.
Hissing and squeaking are normal
MRCOOL's and Senville's manuals list the same sounds as normal:
| Sound | Cause given |
|---|
| Low hiss while running | Refrigerant flowing between the indoor and outdoor units |
| Hiss at start, stop or defrost | Refrigerant stopping or changing direction |
| Squeak after running in heat mode | Plastic parts expanding and contracting |
| Rush of air | The louver resetting |
The unit also makes different sounds depending on its mode, MRCOOL adds. In a cold climate, where a mini-split spends most of the year heating and defrosting, our guide to the quietest mini-split for cold climates ranks cold-rated heads by their heating-mode figures and collects what makers say about defrost noise.
For the full set of winter sounds, from the whoosh of the reversing valve to steam off the outdoor unit, and the grinding, squealing or banging that makers say needs a technician, see our explainer on which heat pump sounds are normal in winter.
It can. Senville's manual warns that its Silence function can lower performance by reducing operating frequency, so use it at night once the room is comfortable, not to cool a hot room.
Most units have a silent or mute setting, and the low indoor figures describe it. On Pioneer's units, Mute runs the indoor fan at its lowest speed; our Pioneer mini-split decibels page lists the Mute figure for every current Pioneer system, with wall units from 26 dB(A).
What size mini split is best for a bedroom?
A 9,000 BTU head, judged by its slowest indoor speed and the mode the maker measured it in.
In a bedroom the head hangs a few feet from the pillow and runs until morning while the compressor sits behind a wall. The World Health Organization's noise fact sheet sets a night target for the whole bedroom of under 30 dB(A).
Sort the figures by mode before ranking them. In cooling, Fujitsu's Altair 500 9k lists 19 dB(A) on Quiet and Mitsubishi's MSZ-FS09NA 20 dB(A) at its lowest speed; in heating, Fujitsu lists 21 dB(A) and Mitsubishi 20 dB(A), the lowest heating-mode figure among the systems here. Klimaire's 30 dB(A) on Mute is a cooling figure. MRCOOL's 18 dB(A) on Si carries no mode, which puts it in a group of its own, and Senville's 17.5 dB is plain dB under a header that does not name its speed.
Buy the smaller head.
MRCOOL's catalog prints the same 43/39.5/33.5/24/18 dB(A), Turbo to Si, and the same 54 dB(A) outdoors for its 9,000 BTU DIY 5th Gen as for the 12k pick, with a 25 ft line set, a maximum coverage area of up to 400 sq ft under ideal installation conditions, and an "As Low As" price of $2,329. The DIY Select 9k lists 43/35/31/22/18 dB(A) indoors, 54 dB(A) outdoors and $1,249, with an 11.5 ft line set that keeps the outdoor unit close to the bedroom wall. Neither 9k is a pick, but their figures share a table with the 12k picks.
For room size, Klimaire gives its 9k a suitable area of up to 200 sq ft, Pioneer 350 to 500 sq ft for the Essenza 12k and Senville 450 to 750 for the LETO 12k. A 12 by 14 ft bedroom is 168 sq ft.
The controls count too. Sleep on MRCOOL and Senville units adjusts temperature, not fan speed: the cooling set point rises 2°F after one hour and 2°F more after the next, and the function stops after 8 hours. Nobody here publishes a sleep-mode figure. Pressing Fan, Turbo or Sleep cancels Mute on Pioneer units, whose manual adds that in heating the fan speed cannot be set manually. Pioneer's remote has a DISPLAY button for the indoor unit's LED display, and MRCOOL's MS-5 remote manual says "Press the LED button to turn on and turn off the display of the indoor unit." Check the manual of the model you buy before mounting a head whose panel faces the bed.
Under a bedroom window, compare outdoor figures within one mode: Fujitsu lists 46 dB(A) and Mitsubishi 48 dB(A) in cooling, while Klimaire's 50 dB(A) and MRCOOL's 54 dB(A) state no mode. After the unit is switched off, MRCOOL's and Senville's manuals add, the outdoor fan runs in reverse for 70 seconds to blow off dust.
Five mini-split buying mistakes
The outdoor unit is what your neighbors hear.
Fujitsu alone explains its method.
Installing it yourself when the warranty needs a pro
Senville, Bosch, ACiQ and Mitsubishi all require a contractor.
Bolting the outdoor unit straight to a wall with no isolation
Rubber gaskets, pads or absorbers are what the manuals recommend.
Running silent mode to cool a hot room
It reduces performance, by Senville's account.
