Mini Split Air Conditioners  View Models >>

Mini Split Air Conditioners

Mini Split Air conditioners are a popular and powerful alternative that bridge the gap between window air conditioners and central ac split systems. Mini splits generally cost more than window air conditioners but less than central ac units in initial purchase price. Their installation burden is much the same as well. They are harder and more costly to install than most window air conditioners, but they are not as expensive or time-consuming to install as central air conditioners, though they do require a licensed HVAC professional for installation. Finally, in comparison to window air conditioners and central air conditioners, mini splits tend to be more energy efficient than the window units and less so than the central units.

Now that some properties of mini split air conditioners have been discussed, we can delve into what exactly these units are.

Mini Split air conditioners have a split design, like central a/c- they separate the "hot" and "cold" parts of the air conditioner. Unlike central ac, mini splits don't use ductwork- the two sides of the air conditioner are connected by coolant lines, a condensate line, and electrical lines. This is why they are sometimes referred to as ductless air conditioners. Mini splits are wall-mounted on the inside and outside of a wall. Most mini split air conditioners have one outdoor unit, but some have as many as four air handlers that all connect to one outdoor unit.

Though the specifications of each individual mini split air conditioner may vary, the two parts can generally be separated by distances of up to 40 feet (of coolant, drain, and electrical connections). They can commonly differ in their altitude by about 15 feet at a maximum. The drain, coolant, and electrical lines are usually bundled together in 3" conduit.

Another benefit to mini split air conditioners is that many units also function as heat pumps, so they can cool in the summer and heat in the winter for year-round comfort.

Choosing a mini split air conditioner

Once you've decided to go with a mini split air conditioner, there are a few important things to consider when deciding which unit is right for you:

  • Your BTU requirement- This is probably the first and most important consideration. You want to get a unit with a capacity as closely matched to your needs as possible. A unit that is not powerful enough will run constantly and will never properly cool the room. A unit that is too powerful will "short cycle"- it will cycle on and off over and over again, only remaining on for short periods of time. Short cycling is bad for the compressor- it could substantially shorten the life of the air conditioner, and the air conditioner will not dehumidify appropriately- so while the air in your room might be a comfortable temperature, there could be an uncomfortable level of humidity. The ideally sized unit will run at its maximum capacity on the few hottest days of the year and run somewhat under capacity at other times.
  • Your area to be cooled- This is closely linked with your BTU requirement. You should keep in mind that even if a split system has the appropriate BTU capacity for your area, it might not circulate air adequately. You should figure out how many air handlers you will need to cool your area. For example, one air handler would likely cool one room- even a large room- well. However, it would probably not work well for cooling an entire house or several different rooms- unless the house has an "Open architecture", there just probably aren't proper channels for airflow.
  • The energy efficiency- You should be mindful of the SEER of the air conditioner that you choose. A higher SEER is better, and a higher SEER air conditioner often costs less in the long run than a less efficient unit. Additionally, many local utility companies offer discounts on high SEER air conditioners.
  • A consultation with the installing HVAC professional- Before purchasing a mini split, you should consult with the HVAC professional who will be installing your mini split. They will help you with the above-listed considerations

After the above considerations have been taken into account, you might consider these other options:

  • Air conditioner vs. air conditioner/heat pump- An air conditioner-only mini split may be less expensive, but if you live in a climate with widely varying temperatures, you might consider a model that cools and heats for year-round use
  • Electronic vs. manual controls- Most units come with electronic controls, which offer more precise control and more features, but manual controls can be simpler and less expensive
  • Remote control- A remote is often very convenient, and if the air handler is mounted high on the wall, the remote control is a necessity!
  • Air filtration- all models have some form of air filter. Better models have better filters that can clean your air while air conditioning
  • Timer and sleep function- a timers allows you to save energy by only running the air conditioner at set times. For example, you might set the air conditioner only run when you anticipate being at home- and not wasting energy by cooling your room when no one is in the room. Sleep timers also help save energy by cooling less after the air conditioner has been running for a set time. This way, you set the air conditioner to run while you are going to sleep and it continues running while you sleep, but at a lower level (i.e., the temperature in the room is allowed to rise a bit) while you sleep
  • Louver adjustability- the more ways you can adjust the louvers (up/down, side-to-side), the more options you have for directing airflow. Also, some units can be set to "swing", so they blow out cool air from several different positions.
  • Air output- almost all models have at least two different settings for airflow. You might want more settings to increase the versatility of cooling. Also pay attention to the Cubic Feet per Minute (CFM) rating. CFM is a measure of the volume of air blown. The higher the CFM, the more airflow the unit kicks out
  • Air conditioner physical size and appearance- some air conditioners are smaller and/or more pleasing to the eye than others. Usually this would just be a consideration for the air handler, as the outside unit is outside and is less of a concern


Mini split air conditioners should be installed by certified HVAC professionals. To find an installer in your area, I suggest you check the yellow pages for HVAC, heating, or air conditioning.

Installation questions

Why does a HVAC professional need to install a mini-split?

Mini split air conditioners require some complex installation, including cutting holes in your walls to run the conduit for the coolant, electrical, and drainage lines. Also mini splits are not usually sold charged with refrigerant, and you need a certified HVAC professional to charge them with the proper amount of the proper refrigerant.

Why aren't mini splits sold charged with refrigerant?

Due to the installation process, refrigerant must be added to the mini split air conditioner after installation.

How large of a hole will be cut in my wall for the conduit?

Generally, the conduit requires a hole of about 3" diameter.

More information on window air conditioners: What is "Mini-split" Anyway?
This Old House: Ductless Air Conditioning Ductless Mini-split