Are mini splits quiet, inside and outside?
Yes indoors: MRCOOL lists its DIY 5th Gen 12k at 18 dB(A) on its silent speed, but every mini-split we checked also publishes an outdoor figure, from 46 to 63 dB(A) among the units we list.
Every mini-split we checked publishes two kinds of figure, one for the indoor head and one for the outdoor unit.
Indoor, usually for each fan speed. MRCOOL, for example, lists its 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. The top end is what you hear while it works hard. If the head is going in a bedroom, the bedroom section below groups those lowest figures by the mode each maker states.
Outdoor, usually one figure. This is what you hear on the patio and what your neighbors hear. Among the units we list, 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 our 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 and not the other. Klimaire's DIY kit has the lowest outdoor figure of the DIY kits, 50 dB(A), but its quietest indoor figure is 30 dB(A). MRCOOL's kits reach 18 dB(A) indoors, but 54 dB(A) or more outside. Decide which side matters more for your home.
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.
If you are weighing a ducted system for the whole house instead, our guide to central air conditioners and heat pumps compares outdoor condensers that publish AHRI 270 sound ratings.
For a condo, addition or garage office that already has a sleeve about 42 inches wide under the window, our guide to the quietest PTAC units compares the packaged units that cool and heat from one chassis.
How are mini split decibel ratings measured?
Mini-split makers mostly do not say how they measure their decibel ratings, and only one maker we read, Fujitsu, explains its method. Fujitsu says its figures are measured in its own anechoic chamber, a room built to absorb echoes, and 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 say nothing on method, but its service manuals do, and our Mitsubishi mini-split decibels page quotes their anechoic-room note and lists every current M-Series figure.
Klimaire says its indoor figures are measured in cooling mode. The rest, including MRCOOL, Senville, Pioneer, Bosch and ACiQ, give no distance, standard or mode. So a 17.5 from one brand and an 18 from another are, for practical purposes, the same. 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, so we cannot say which speed its 17.5 dB belongs to. 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, you can install a pre-charged mini-split kit yourself, but read the warranty first, because some makers require a licensed contractor. Pre-charged "quick connect" kits let a handy homeowner connect the lines without vacuum pumps or refrigerant gauges. But the warranty terms vary widely, and this is the biggest decision after noise.
- DIY allowed: MRCOOL's warranty applies to systems installed according to its installation instructions, though it says a licensed contractor may be necessary where the law requires one. Klimaire says DIY installation is allowed if you follow local code, and gives full cover if you register within 45 days.
- Professional required: Senville says its warranty is valid only if a licensed professional installs the unit. Bosch, ACiQ and Mitsubishi also require a licensed or qualified contractor.
- In between: Della honors registered DIY installs, but with parts-only cover.
Pioneer's Essenza uses a standard flare line set that has to be evacuated, so it is not a plug-together kit, whatever the warranty says.
How do you install a mini split so it runs quietly?
Put the outdoor unit where its noise will not disturb others, on a solid base that will not vibrate, and hang the indoor unit on a solid wall. The manuals share a few rules that matter for noise.
Choose the site with neighbors in mind. MRCOOL says not to install the outdoor unit where its noise will disturb others. Pioneer says to pick a location where the discharge air and operating sound will not disturb others.
Use a solid, vibration-free base. MRCOOL's checklist asks for a location that is firm and solid and will not vibrate. It says to fit rubber gaskets on wall brackets where allowed. Pioneer says to install rubber vibration absorbers if the system could pass vibration into a structure. Della suggests rubber foot pads, and Klimaire sells a rubber vibration pad set.
Do not cut the line set too short
Senville's LETO manual says a minimum pipe run of 9.84 ft is needed to minimize vibration and excessive noise.
Mount the indoor unit on a solid wall. Pioneer says not to install it on a wall that is subject to vibration.
Is it normal for a mini split to make noise?
Yes, some mini-split noise is normal, and MRCOOL's and Senville's manuals list the same normal sounds:
- a low hiss while running, from refrigerant flowing between the indoor and outdoor units
- a hiss when the system starts, stops or defrosts, as the refrigerant stops or changes direction
- a squeak after running in heat mode, as plastic parts expand and contract
- a rush of air when the louver resets
MRCOOL adds that the unit makes different sounds depending on its mode. 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.
Yes, silent mode can cost a mini-split performance: Senville's manual warns that its Silence function can lower performance by reducing operating frequency. 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. Pioneer says its Mute mode runs the indoor fan at its lowest speed, and 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 mini-split head is the size to buy for a bedroom, judged by its slowest indoor speed and the mode the maker measured it in.
The head in a bedroom hangs a few feet from the pillow and runs until morning, while the compressor sits behind a wall, so buy on the lowest indoor speed and the mode the maker measured it in. 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, so it sits 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 our 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 the figures share a table with our 12k picks.
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 matter too. MRCOOL's and Senville's sleep functions adjust temperature, not fan speed, raising the cooling set point 2°F after one hour and 2°F more after the next, then stopping after 8 hours; no maker here publishes a sleep-mode figure.
Pioneer's manual says pressing Fan, Turbo or Sleep cancels Mute, and 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."
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. MRCOOL's and Senville's manuals add that after the unit is switched off the outdoor fan runs in reverse for 70 seconds to blow off dust.
What should you avoid when buying a mini split?
The usual mini-split buying mistakes are judging only the indoor figure, comparing brands too closely, installing it yourself when the warranty needs a pro, skipping vibration isolation and running silent mode to cool a hot room.
The outdoor unit is what your neighbors hear.
Only Fujitsu says how it measured.
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
The manuals recommend rubber gaskets, pads or absorbers.
Running silent mode to cool a hot room
Senville says it reduces performance.
