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Mini Split Air Conditioner Buying Guide

Mini-Split AC Buying Guide

Ductless mini split systems are increasing in popularity because they offer effective, efficient cooling throughout homes or offices. These unique systems consist of an outdoor condenser unit and at least one indoor unit that distributes cool air. Models with multiple indoor units are referred to as "multi-zone" mini-splits, because they add targeted cooling to multiple areas of a home.

Ductless mini splits don’t need to be vented like many room ACs, so they're a great option for rooms without windows or access to exterior walls. These systems also provide greater temperature control since each indoor unit works independently and can be set to different temperatures—allowing you to cool certain parts of your home without cooling the entire space. This zone cooling helps decrease energy usage since you're only cooling parts your home that you actually use as opposed to cooling your entire home like a central air conditioner.

Many models offer a Heat mode, typically known as mini-plit heat pump, and keep you comfortable all year. Most mini splits have remote controls and various other features, including programmable timers, automatic restart, and auto-swinging louvers.

For quick access to the sections in this buying guide, click the links below:

Components of Mini-Split ACs

Ductless systems are made up of 4 components:

  • Condensing Unit: The condenser is located outside the home or building being cooled. Its condenser coil pumps the cool air through refrigerant lines that connect to the unit or units indoors.
  • Refrigerant Lines: These charged refrigerant lines connect the outdoor unit to the indoor unit or units. They're small tubes of cooling refrigerant and are called line sets and connect the units either through a small hole in the wall, or in rare cases, through a window.
  • Indoor Unit or Units: These can be wall-mounted, suspended from the ceiling, or mounted in the ceiling. Cool air is released into your home through the indoor unit or units.
  • Remote Control or Wall Monitor: This controls the entire system and allows you to change temperature, modes, and other settings.

Common Uses

These ACs are popular in homes without ductwork, rooms with limited window space, garages, and spaces with old or inefficient central air cooling systems. They're also used in new construction, home additions, multi-family housing, and in poorly air conditioned rooms. Older homes that don't have ductwork for conventional cooling systems or businesses with hot spots (such as doctor offices) are also common places for ductless mini-splits.

Main Advantages

  • Quiet: Since the compressor is housed outside, the only indoor noise is from the unit's fan, making them quieter than window or thru-wall ACs.
  • Zone Cooling (and Heating if included): Zone cooling lets you cool one room or area of your home at a time. For example, you can keep your bedroom AC off until you go to bed. You can also only place indoor units in spaces you use often, so you'll be comfortable without cooling the rest of your home. While central ACs cool your whole home, including areas you rarely use, zone cooling lets you only cool specific areas of your home, so you don’t waste energy cooling areas you're not in.
  • No Ducts: You don’t need to worry about dirty ducts spreading allergens or other particles around your home, because they don’t use ductwork. In addition, nearly all ducted systems lose some percentage of performance and efficiency due to leaks, cracks, or disconnections—no ductwork means no loss of performance.

Zones: Single- vs. Multi-Zone

A single-zone ductless split system cools an area of your home using 1 outdoor and 1 indoor unit. These are popular in bedrooms or rooms that aren't ducted for central air conditioning. The main consideration with single-zone ACs is if the unit has enough power to cover your room's square footage. View single zone ductless mini splits.

Multi-zone mini splits work just like single-zone models but cool more parts of your home or business. Each indoor unit (representing a zone) connects to the outdoor unit through the refrigerant lines. There are generally up to 4 indoor zones. If you don’t have central air conditioning, consider using a multi-zone system to cool different areas of your home—which can be on multiple floor levels thanks to long refrigerant lines. Multi-zone models are popular in basements, doctor's offices, and apartments. The single outdoor unit is equipped to handle all interior units, though usually all can't be used on the highest level at the same time. View multi-zone ductless mini splits.

Size and Power

Each indoor ductless unit offers a set number of BTUs of cooling power. For single-zone units, you simply need to know the number of BTUs associated with the indoor unit and make sure it fits the square footage you're cooling. 

For multiple zone systems, both the outdoor and indoor units have a BTU rating attached to them. One benefit of a ductless split system is each indoor unit runs independently.

Check out our square footage and BTU comparison chart below. Keep in mind if you're purchasing a multi-zone system, you need to look at the BTU rating for each unit (or zone). For example, an AC may use 30,000 BTUs total, with each indoor unit using 9,000 BTUs and the outside unit using 12,000 BTUs.

Area To Be Cooled (Square Feet)

Capacity Needed (BTUs Per Hour)

100 to 150 square feet

               5,000 BTUs

150 to 250 square feet

               6,000 BTUs

250 to 300 square feet

               7,000 BTUs

300 to 350 square feet

               8,000 BTUs

350 to 400 square feet

               9,000 BTUs

400 to 450 square feet

               10,000 BTUs

450 to 550 square feet

               12,000 BTUs

550 to 700 square feet

               14,000 BTUs

700 to 1,000 square feet

               18,000 BTUs

1,000 to 1,200 square feet

               21,000 BTUs

1,200 to 1,400 square feet

               23,000 BTUs

Environmental conditions should also be taken into consideration when sizing your space for a mini split AC. If any of them are applicable to you, increase the number of BTUs by the percentage shown:

Environmental Condition

% BTU Increase

Ceiling Height: If your ceilings are higher than 8 feet, you should increase your number of BTUs.


Insulation: Poorly insulated areas require more power to cool.


Climate: In areas with seasonal temperatures often exceeding 90 degrees F.



Voltage is another important consideration for your ductless mini split's power requirements. Smaller-powered mini splits use a standard 110- to 120-volt plug, which most homes are wired for, but larger units require higher voltage. These models use a 220- to 240-volt plug; make sure your home's voltage matches your unit's before purchasing. Using the incorrect voltage can cause the circuit to break, a loss of efficiency, or even cause a fire.


Installing mini split ACs require professional installation since you run the refrigerant lines indoors from outside your home through a small hole in your wall. You'll need to contact an HVAC professional to be sure your AC is installed to run as effectively and efficiently as possible.

There are always exceptions to the rule, however, and one model we carry doesn’t require professional installation. You can install the Friedrich Breeze much easier than traditional models since its pre-charged refrigerant lines can run through a window or a wall. Read more information on the Friedrich Breeze Mini Split AC.

Indoor Unit Location Options

Most indoor air conditioning units are hung on a wall using included brackets, while other models are hung from the ceiling. Be sure your refrigerant lines will reach each indoor hanging unit before you install them. Check where your indoor units can be installed before you purchase a mini split AC.

Energy Efficiency

Mini split systems are efficient ways to cool your home. Their efficiency is measured by a Seasonal Energy Efficiency Ratio (SEER). The higher the SEER, the more efficient the unit. Currently, federal requirements state mini splits must have a 13.0 SEER rating to be used in the United States. Another energy rating to look out for is Energy Efficiency Ratio (EER), which looks at energy usage per square foot of cooling. SEER and EER both rate your product's efficiency, so keep an eye out for one or the other when comparing products.

Along with SEER (and possibly EER) ratings, your model should come with an estimated yearly operating cost. This is an average dollar amount associated with your model based on operating and maintenance costs—if you're comparing 2 models, check out the estimated yearly cost before purchasing.

If a model is extremely efficient, it can become Energy Star-rated. In order to become Energy Star-rated, models must prove to significantly contribute to energy savings and offers products and performance demanded by consumers. Replacing an inefficient cooling system with a mini-split can cut your heating and cooling costs by up to 30%.

What Makes Mini Splits So Efficient?

  • More control: In traditional heating and cooling systems, you have one thermostat that controls the temperature in your entire home. Using a mini-split AC lets you control the temperature in each zone, so you can make sure commonly-used spaces are more comfortable than rooms you rarely use. This zone cooling helps save you on energy costs since you aren’t paying to cool your entire home, but only areas you commonly use.
  • Ductless: In traditional ACs, ducts are used to distribute cool air throughout your home. About 20% of that air is lost due to leaks, holes, and poorly connected ducts. Removing this step—like mini splits do—saves you energy and money.
  • Heating and Cooling: Mini splits can deliver cool and warm air from the same unit, which traditional ACs don't offer. This avoids having to install and run two separate units.

Compressor Types: Inverter vs. Rotary

The outdoor unit is the compressor, and it's one of the most important parts of a mini-split AC. The 2 main compressor types for mini splits are inverter and rotary. A rotary compressor turns on and off while working to maintain your set temperature, while an inverter compressor uses only enough power to reach the desired setting, then idles at that setting until more power is needed.

A rotary compressor will turn on with full power, while an inverter compressor only uses enough of its resources to reduce the room temperature to your desired setting. Many people prefer inverter compressors because they save energy by not constantly turning on and off. Most new ductless mini splits use inverter compressors.

Additional Modes

Mini splits can include multiple modes to keep your home full of crisp, cool air in the summer and warm air in the winter. Additional modes are popular for people who don’t have central air conditioners and use their mini-split AC as their primary cooling option.

Keep an eye out for these modes for year-round comfort:

  • Heat: Mini-split heat pumps transfer heat from one area to another, so turn on heat mode during cooler months with virtually no hassle. You control this mode just like you would Cool mode, and you can typically set your thermostat as high as 88 degrees F. Models with built-in heaters have a separate BTU-rating for their heat option, so consider your room size if you're looking for a model with heat.
  • Dehumidify: Remove excess moisture from your air using a Dry or Dehumidify mode. This mode is popular in basements or areas of the country with extremely humid conditions.
  • Fan-Only: Use Fan mode to distribute and circulate air around your space without using Cool mode.
  • Automatic: Let your AC do the work for you! Simply select Automatic mode and it selects a mode and fan speed based on your ambient room temperature.
  • Sleep: The Sleep function maintains a pleasant room temperature with quiet operation while you rest.


Mini split ACs come with various convenient features:

  • Programmable Timer: Program your mini-split to turn on or off up to 24 hours in advance. For example, set it to turn on right before you get home from work—you'll walk into a cool home without running your AC all day.
  • Remote Control: A common feature is a remote control that makes changing indoor unit settings simple. Most models come with a remote since indoor units are hanging on a wall or ceiling.
  • Adjustable Airflow: In some models, you can adjust airflow on the remote. With others you manually move louvers to direct cool or warm air throughout your space. You can also look for louvers that swing automatically to direct airflow up and down.
  • Washable Air Filter: An air filter catches unwanted allergens and particles before they enter your home. Look for one that can be washed and replaced to save on replacement filters.
  • Automatic Restart: In the event of a power failure, mini-splits automatically resume operation in the last programmed setting once power is restored. This function not only protects the compressor, but it also prevents circuit breaker damage.
  • Minimum Heat Operation: In models with heat, set this mode and your heater will maintain a temperature to ensure your room doesn’t get too cold (typically around 50 degrees F).

Consider This

Ductless mini splits are similar to fans in that they only cool areas they can reach. Walls, doors, and other obstacles will block cool air from reaching certain places. Make sure your indoor unit's can reach the entire space you're looking to cool. If not, you may want to consider installing a multi-zone system or window air conditioner in each individual space.

Other Resources

Still Have Questions?

For more information on ductless mini-splits and other indoor air treatment solutions, shop our products and visit our Knowledge Center. Not sure what's best for you? We can take the guesswork out of decision-making. Contact our product experts toll free at 1 (800) 934-9194. We want to help you make your indoor environment a healthy one.

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