Mini-split ACs are ductless heat pumps that control temperature by transferring refrigerant between an outdoor compressor and indoor evaporators. Rather than blowing cool or warm air past a large evaporator through ductwork, refrigerant is piped directly to small evaporators in every room. Invented more than 60 years ago to retrofit older homes built without ducts, mini-split AC systems are now catching on in warmer climates throughout the USA as an alternative to central air.

How Do Heat Pumps Work?

Air conditioners are heat pumps that work by forcing pressurized refrigerant through evaporator coils inside your home. The liquid refrigerant absorbs heat to cool indoor air, turning it into a gas that is pumped back to the compressor where heat is released into the outside air. By simply reversing this process, the same unit can also heat your home by transferring warmth from the compressor to the inside air. Heat pumps are less efficient than traditional furnaces in subzero weather but are very popular in areas with milder winters. 

Advantages & Applications

With a ductless heat pump, air blows directly through small evaporators in every room. These allow you to set the temperature separately for every zone in your home, or only heat and cool rooms when they are occupied. For older homes with no ductwork, it can be prohibitively expensive to install central air but mini-split ACs only require the installation of small pipes to carry refrigerant. Homes with inefficient and expensive central air can be converted to ductless systems which are up to 60% more energy efficient than standard AC units. Additions, sunrooms, guest houses, basements, man caves, barns, and garages, where extending ductwork is not possible, can be heated or cooled with one mini-split system. Smoking rooms and kitchens can also utilize ductless heat pumps so smoke and cooking smells are not circulated through the entire house. 

Elegant, Quiet, Clean Air

Mini-split evaporators contain an air filter, blower fan, and refrigerant coils inside a rectangular unit. They are often installed on an outer wall above eye level. Elegant designs are available to fit any decor and they can even be hidden behind shelving or mounted inside the ceiling. Most units come with a convenient remote-controlled thermostat. There is no need to inspect ducts for leaks or for annual cleaning, because easy to replace filters purify the air in every room. Another advantage of mini-splits is they are quieter than central air.

Cost & Energy Efficiency

Energy Star Certified mini-split ductless heat pumps use around 60% less electricity than standard electric heaters1. Eliminating leaking ducts can also save at least 30% of the energy consumed by a standard AC 2. An interesting aspect of heat pumps is that they can transfer more energy than is required to power them, using the most efficient heating and cooling technology on the market. If you rely on radiators, baseboard heaters, propane, or natural gas to heat your home, switching to ductless heat pumps is a great way to save money. 


Professional installation is necessary to ensure the system is able to heat and cool every zone in your home. Ductless heat pumps are often covered by a warranty which can be voided if they are not installed by a licensed HVAC professional. Refrigerants are toxic and can damage the environment if not safely handled. An outdoor compressor must be installed with pipes running through the outer walls of your home, so holes must be completely sealed against loss of insulation, pests, and rain. The process will take several hours, or as long as a few days for complex installations depending on your home’s floor plan. 

When you decide to install or upgrade a mini-split AC, give Long HVAC a call to schedule a free consultation. We’ll review all the options available, answer all your questions, and provide a comprehensive estimate for parts, labor, and energy efficiency.


[1] – Ductless Heating and Cooling Products

[2] Department of Energy – Ductless Mini-Split Air Conditioners