By Anne Fonda
A mini-split HVAC system heats and cools (or just cools) one or more rooms without using a system of ductwork. This is why these systems are also called ductless HVAC systems. A mini-split system is similar to a traditional ducted split system, in that there is an outdoor unit, usually a mini-split heat pump, along with one or more indoor units.
Indoor units are available to suit your style and include:
Instead of the indoor and outdoor units connecting to a duct system to spread heated or cooled air throughout your home, with a mini-split system, each room, or zone, has its own indoor unit. The indoor and outdoor units are connected by refrigerant lines.
The outdoor component (most frequently a multi-zone heat pump or mini-split heat pump) contains the compressor and the condenser. In the summer, it delivers cool air to the indoor unit(s) via a conduit that includes the refrigerant lines, power cable, and condensate drain line. In the winter, the heat pump reverses the heat exchange process to deliver heat to each zone.
A ductless HVAC system can have one or more indoor units, depending on your needs. The indoor unit houses the evaporator and a blower fan that distributes the cool air evenly. It connects to the outdoor unit via the conduit.
You set the system to heat or cool, and set individual temperatures for each unit based on your needs and comfort level. Each indoor unit comes with a remote control for ease of use.
Let’s explore your options further.
A single-zone ductless system is ideal when you only need to heat or cool one room or space. A mini-split for a garage is something that is growing in popularity. A mini-split air conditioner can also help you keep your cool in a workout room. Or, if you’re adding a home office but don’t want to pay to extend the ductwork, a mini-split AC and heat system can be a perfect comfort solution.
Multi-zone ductless HVAC systems are energy-efficient options for new construction, older homes without ductwork, and other areas that need a boost in heating and cooling comfort. You get zone control where you can adjust the mini-split thermostat settings for up to 5-8 separate rooms, depending on the system you choose.
All of the units must be set on the same mode – heat or cool. You cannot heat one room while cooling another if you have one outdoor unit. Popular configurations include:
If you have boiler heat or baseboard heating that you’re satisfied with and just need ductless cooling, multiple mini-split air conditioning units will keep your whole house cool and comfortable.
But remember, according to ENERGY STAR®, because they transfer heat instead of generating it, ENERGY STAR®-certified mini-splits can use 60% less energy than standard electric radiators.
You can’t necessarily say mini-split air conditioning is better or worse than central air conditioning. It all depends on whether you have existing ductwork or not and what your cooling needs are.
If you have ductwork throughout your home, a central air conditioning system makes sense – whether you have a central AC unit or a heat pump take care of the cooling.
A ductless system with multiple ductless mini-split units makes financial and comfort sense if you live in an older home without ductwork. You can add AC mini-splits (cooling only) or a heat pump mini-split to provide both heating and cooling, depending on your needs.
In addition, if you have an area that needs a boost of cool air, such as an exercise room, a mini-split AC unit makes sense. A mini-split AC unit for the garage is becoming a popular garage cooling solution.
As with all HVAC systems, correct sizing matters. The best way to properly size your new ductless system is to work with an HVAC professional who designs and installs mini-split systems regularly.
To get a ballpark figure, you can take the square footage of the space you want to heat and cool and determine how many British Thermal Units (BTUs) you need. One BTU represents the amount of energy it takes to raise or lower the temperature of water by one degree Fahrenheit.
The basic BTU formula for mini-split sizing is square footage x 20. For example, a 200 sq. ft. room would need 4,000 BTUs. Remember, this is just a rough estimate. There are many other factors to consider for correct sizing.
For example, ceiling height, sun exposure, and insulation may require a larger capacity. All of that being said, here’s a table that gives you a general idea of the heating and cooling capacity you would need for a given space.
| Space size (sq. ft.) | Unit Size (BTUs) | Unit Size (Tons) |
|---|---|---|
| 200-300 sq. ft. | 6,000 BTU mini-split | .5-ton mini-split |
| 300-450 | 9,000 BTU mini-split | .75-ton mini-split |
| 500-600 | 12,000 BTU mini-split | 1-ton mini-split |
| 650-800 | 18,000 BTU mini-split | 1.5-ton mini-split |
| 850-1,100 | 24,000 BTU mini-split | 2-ton mini-split |
| 1,000-1,450 | 30,000 BTU mini-split | 2.5-ton mini-split |
| 1,500-1,700 | 36,000 BTU mini-split | 3-ton mini-split |
If you’re used to seeing capacity expressed in tons, know that 1 ton = 12,000 BTUs.
The mini-split heat pump provides the power behind the heating and cooling. You’ll need one powerful enough to heat and cool your space. You’ll need indoor units that have the capacity you need as well.
Indoor units are available in 6, 9, 12, 15, 18, 24, 30, and 36 kBTU/h. Different units are available in different capacities. They also have varying energy efficiency levels, with SEER2 up to 33.1 and HSPF2 up to 13.5.
The easiest way to find the best mini-split heat pump and compatible indoor units for your space is to consult with an experienced HVAC professional.
This question is hard to answer without knowing the specifics of your home and your heating and cooling needs. Your ductless HVAC system cost will vary widely depending on the heating and cooling capacity, efficiency ratings, choice of indoor unit, how many zones you want, complexity of the installation, labor costs, and other factors.
Be aware that certain ductless systems are ENERGY STAR®-certified and may qualify for tax credits and rebates. Contact your local Trane dealer for specific pricing information.
We don’t believe that installing a mini-split system is a DIY job. Trane/Mitsubishi ductless systems are high-tech, sensitive pieces of equipment and can only be installed by an authorized dealer. Ductless mini-split systems require working with refrigerant lines and high-voltage electric lines. Your state may require a licensed professional to install a mini-split AC unit or mini-split heating and cooling.
Attempting a mini-split installation on your own could lead to a system that doesn’t work properly, a refrigerant leak, damage to your home, and a voided warranty. Stick with experienced mini-split installers near you to help ensure you get the most out of your system.
Maintenance of ductless mini-splits is pretty easy. Keep the outdoor unit and indoor units clear of obstructions. Dust or wipe down the interior units with a soft, damp cloth. Clean the reusable air filters regularly. With regular maintenance, these filters can last up to 10 years!
In addition to this DIY maintenance, you should schedule regular maintenance (twice a year) with your local HVAC company – preferably the company that installed the system, as they will know what to look for when servicing your units.
There’s a reason Trane/Mitsubishi Electric ductless systems are the top-selling brand in the U.S. A pioneer in the industry, Mitsubishi introduced ductless heating and cooling in Japan in 1959, where it has been the norm for decades. The two companies have joined forces to bring superior mini-split technology to the mainstream in the United States. Our products offer exceptional energy efficiency, superior performance in frigid temperatures, and the indoor units are whisper-quiet.
When we compile information like this, our goal is to help homeowners make informed decisions. We work with HVAC engineers and HVAC professionals with decades of experience so that we can provide you with accurate and up-to-date information. Our glossary items and blogs undergo expert review to ensure you get the information you need.
Read through our ductless product brochure for full details on these energy-efficient heating and cooling solutions. For even more guidance, read our blog Is a mini-split system right for your space? Then set up a no-obligation consultation with your local Trane dealer specializing in ductless system design and installation.
Anne Fonda, Content Writer
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.
When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by Ryan Goodwin, Senior Product Manager, Ductless
A ductless HVAC system (also called a ductless mini-split or ductless multi-split) is any HVAC system that can heat and/or cool your home without the presence of ducts. Ductless HVAC systems are designed to control the temperature in just one room or space, as opposed to the entire home.
Ductless heat pumps work to both heat and cool single spaces or rooms within your home where ductwork is not present. Homeowners can install up to five indoor ductless units throughout their home, all connected to just one outdoor unit, in order to cool multiple spaces at once.
Ductless air conditioning cools just one room or single space where ductwork is not present in your home. Homeowners can install up to five indoor ductless units throughout their home, all connected to just one outdoor unit, in order to cool multiple spaces at once.
Dealers can answer questions, help you find the right products for your home, and repair your system.
Connect with our Customer Care team about your products, warranties, and dealer concerns.
Available Monday – Friday from 7am to 5pm CST
A phone