A mini-split is the quietest way to cool or heat a single room. The loud part, the compressor, sits outside, and the indoor unit is little more than a fan. So it is no surprise that mini-split makers compete on noise, and publish more of it than almost any other category.
We read the catalogs, spec sheets, manuals and warranties for fifteen mini-splits from ten brands, including several you can install yourself. Here is how to read the numbers, which to buy, and which warranties you lose by doing it yourself.
Our 6 picks are listed above, with full specifications for each.
Two numbers, not one
Every mini-split we checked publishes two kinds of figure.
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. The low end is what runs overnight once the room is at temperature. The top end is what you hear while it works hard.
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.
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.
Only one maker we read 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."
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. For more on this, see why you cannot compare dB ratings across brands.
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.
DIY or pro install: read the warranty first
This is the biggest decision after noise. Pre-charged "quick connect" kits let a handy homeowner connect the lines without vacuum pumps or refrigerant gauges. But the warranty terms vary widely.
- 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.
Installing for quiet
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.
Sounds that are normal
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.
Silent modes have a cost
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. But 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.
Mistakes buyers make
Looking only at the indoor figure. The outdoor unit is what your neighbors hear.
Comparing figures across brands too closely. 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.
How we chose
We read each maker's US catalog, submittal or spec sheet, installation and owner's manuals, and warranty. We recorded every indoor and outdoor noise figure in the maker's own words, with any speed, mode or measurement basis given. We compared capacity, efficiency, voltage, heating range, installation type and warranty terms, and recorded the price on the maker's own site where one was shown.
We did not measure decibels ourselves. We ranked first on published indoor figures at the lowest speed, then weighed the outdoor figure and whether you can install the unit yourself without losing the warranty. MRCOOL, Klimaire, Fujitsu, Mitsubishi, Bosch, ACiQ and Gree show no price on their own sites, so check the price on the day you buy. We could not check Cooper and Hunter or LG, whose sites blocked us.
New to the units? Read dBA explained. To decide what figure to aim for, see how quiet is quiet enough, room by room.
