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What is a ductless heating and cooling system?

A ductless heating and cooling system is a highly efficient zonal heating and cooling system that does not require the use of air ducts. Ductless systems consist of an outdoor compressor unit and one or more indoor air-handling units, called “heads,” linked by a dedicated refrigerant line. Indoor heads are typically mounted high on a wall covering a three-inch hole where the refrigerant line passes through from the outside unit, which is mounted at the base of the house. Each indoor head corresponds with a heating and cooling zone that can be controlled independently.

What are appropriate applications for these systems?

Displacing an existing zonal heating system

Ductless systems are ideal for replacing or supplementing baseboard, wall and ceiling heat, wood stoves, electric furnaces and other electric plug-in space heaters, such as those using propane or kerosene. A cost-effective solution for a small electrically heated home may consist of a single-zone system serving the main area of the house, with existing electric baseboards remaining in bedrooms and bathrooms.

Room additions

A ductless system can also be an ideal solution for a room added onto a house or an attic converted a to living space. Rather than extending the home’s existing ductwork or pipes, or adding electric resistance heaters, the ductless system will provide efficient heating and cooling. Please note that homes that are not primarily electrically heated may not be eligible for utility incentives; check with your electric utility for incentive eligibility requirements.

New construction

New home designs can be adapted to take advantage of a ductless system’s many benefits. Two or more systems can be installed in various zones of the house to simplify installation and minimize refrigerant line length. Please note that homes under construction are generally not eligible for utility incentives, though complete/permitted for occupancy homes are now eligible for incentives in most utility territories; check with your electric utility for incentive eligibility requirements.

How does a ductless system work and how is it controlled?

Ductless heating and cooling systems are reversible, two-way heat pumps that transfer heat between outdoor and indoor air by compressing and expanding refrigerant. Using a refrigerant vapor compression cycle, like a common household refrigerator, ductless systems collect heat from outside the house and deliver it inside the house on the heating cycle, and vice versa on the cooling cycle. Ductless systems use variable speed compressors with inverter technology (AC to DC) in order to continuously match the heating/cooling load, avoiding inefficient on/off cycling of conventional electric resistance and central heating systems commonly associated with uncomfortable temperature variations and high energy consumption.

Ductless systems consist of several parts, including:

  • An outdoor unit that contains a condensing coil, an inverter-driven variable speed compressor, an expansion valve and a fan to cool the condenser coil
  • An indoor unit that contains an evaporator and a quiet oscillating fan to distribute air throughout the living space
  • A refrigerant line-set that is made of insulated copper tubing and is housed in a conduit alongside a power cable, and a condensation drain
  • A remote control that can be used to set the desired temperature and program for nighttime settings

The system is controlled via a remote control that changes temperature and operation mode. Wall-mounted and wi-fi enabled controls are also available.

Do I still need my old heaters?

While a ductless system can be used as a primary heat source, homeowners are encouraged to keep their existing electric heating units as supplementary heating in case of extreme weather conditions or for use in hard-to-reach extremities of the home.

Are ductless systems efficient?

Ductless systems are highly efficient, using 25 to 50 percent less energy than zonal heat types, such as baseboard, wall and ceiling heat or electric forced-air furnaces. Three key factors account for the high efficiency of a ductless system:

1. Ductless systems allow the user to control each heating and cooling zone independently, eliminating the costly overheating and over-cooling common to central air systems. You no longer need to pay to heat or cool unoccupied rooms.

2. While central air systems lose as much as 30 percent of their efficiency through air leaks and conduction in the ductwork, ductless systems distribute air directly to each zone, resulting in 25 percent greater efficiency. Ductless systems use inverter-driven, variable speed compressors that allow the system to maintain constant indoor temperatures by running continuously at higher or lower speeds. Thus, the system can ramp-up or down without great losses in operating efficiency, avoiding the energy intensive on/off cycling common in electric heating systems.

3. Modern ductless systems have extremely good Seasonal Energy Efficiency Ratios, or SEER, between 16 and 22, and Heating Seasonal Performance Factors, or HSPF, that range from 9 to 12 or greater.

How long have ductless systems been around?

Ductless heating and cooling systems were developed in Japan in the 1970s and have since become a preferred heating and cooling system throughout Asia and much of Europe. In the United States, ductless systems have been used in commercial applications for over 20 years.

How much does a ductless system cost?

The average cost of an installed ductless system with a single indoor heating/cooling head is between $3,000 and $5,000. Additional heads and greater heating capacities will increase the cost of the system. Other factors that will affect the cost of an installed system include manufacturer and model, geographical location, refrigerant line-set length, difficulty of installation and installer rates.

What incentives are available for ductless systems?

Many utilities in the Northwest offer customers incentives as high as $1,500 for upgrading an existing electric heating system to a ductless system. Interest-free financing may also be available. Check with your local electric utility for details.

Visit our utility incentives page for a listing of incentives that may be available in your area.

Federal tax credits and additional incentives

Residential energy tax credits for high-efficiency heating, cooling and water heating equipment may be available for qualified equipment. For more information and for a list of qualified ductless systems, visit the ENERGY STAR® website.


The Montana Energy Conservation Installation Credit provides a tax credit for 25 percent of the cost of a ductless heating and cooling system, with a maximum credit of $500 per individual and up to $1,000 for a married couple filing jointly.


Effective January 1, 2013, qualified equipment is eligible for a $350 to $1,500 tax credit from the Oregon Department of Energy. To review qualified equipment and incentives for ductless systems, visit the Oregon Department of Energy’s website.

Additional resources

Visit the Database of State Incentives for Renewables & Efficiency for a comprehensive list of incentives that support energy efficiency in the United States.

How long will a ductless system last?

With proper maintenance and care, a ductless system should perform for over 20 years. Many of the systems installed during the 1980s are still functioning well today. Check manufacturer guidelines for proper maintenance of your system or reference our Ductless Homeowner’s Guide.

What kind of maintenance does a ductless system require?

Ductless systems require basic maintenance to ensure optimum performance, though periodic professional servicing of your system is recommended. In most cases, ductless system maintenance is limited to keeping filters and coils clean, and these tasks can easily be performed by the homeowner. For more information, download our Ductless Homeowner’s Guide or refer to the manufacturer’s maintenance guidelines for your system.

How do I know what size of system my house needs?

Ductless systems are sized to meet the heating and cooling needs of a home’s individual zones. There is a great deal of flexibility when it comes to system sizing as one indoor unit can provide between ¾ and 2½ tons of heating and cooling depending on its BTU capacity rating. Some common capacities for indoor units are 9k, 12k 18k, 24k, and 30k BTU. Outdoor units are sized to meet the combined load of all heating and cooling zones. More than one outdoor unit may be necessary for multi-zone systems.

Work with a qualified ductless Master Installer to make sure you are getting a properly sized system for the heating and cooling needs of your home. Installers in your area can be found here.

What is a Master Installer?

A Master Installer has shown commitment and experience with ductless systems. These installers have successfully completed a technical training, at minimum 25 ductless installations within the last three years and have agreed to program-identified best practices.

Please contact us for more information.