All About Mini-Split HVAC systems

A mini-Split wall unit

Mini-split heat pumps, also known as ductless HVAC systems, have been steadily gaining popularity for their efficiency, versatility, and ease of installation. These compact units offer a unique approach to heating and cooling.  They are often used in rooms separated from the home’s main HVAC system, such as a home office, an ADU, or a converted garage. Homeowners may desire such rooms to be separate from the home HVAC system, but in many cases, such as a garage converted to an ADU, connecting such a room to the home’s main HVAC system is impractical.

 What is a Mini-Split?

All mini-split systems are heat pumps.  They run off electricity and not gas. The operation of a mini-split heat pump is based on the principles of refrigeration. During the cooling mode, the system extracts heat from indoor air and transfers it outside, cooling the interior space. Conversely, in heating mode, the process is reversed as the unit absorbs heat from the outdoor air and releases it indoors, providing warmth during colder months. Installation for this type of system consists of two parts: an indoor unit called an air handler and an outdoor unit similar to a central air conditioner. Though, unlike central heat pumps, a mini-split is smaller in size.

The main difference between a mini-split and a traditional HVAC system is that mini-split systems do not have ductwork. They do not have a central blower that blows air into multiple rooms. They have a single air handler mounted on a wall that blows directly into the room they are installed in. Hence, this is why are they also known as ductless systems.

a mini-split wall mounted air handler
a mini-split wall mounted air handler

Inspecting a Mini-Split

A key disadvantage of mini-splits for inspectors is being able to tell how old a unit is. With central furnaces and air conditioners, there are only so many manufacturers. Most of these manufacturers either label the unit with the date of manufacture or embed the date in the unit’s serial number. On the other hand, there are hundreds of different manufacturers of mini-spit systems, and most of them do not put dates on the units. The other disadvantage is because there are so many different brand names, it’s difficult to distinguish a good brand from a bad brand. So as inspectors, we are unable to tell the age of a mini-split or estimate how much useful life they may have left.

Remote over Thermostat

The other significant difference between mini-split systems and central HVAC systems is how they can controlled.  Central systems usually have one or more thermostats on a wall. Mini-split systems generally do not have a thermostat, but instead have a remote control. Much like a TV remote, if the remote doesn’t have batteries or if you misplace the remote, you can’t control your system! Another quirk is the remotes tend to have small buttons, and each manufacturer’s remote is different. This can make changing from heat to cool difficult. It is important for a homeowner to read the manual for their units to fully understand how their unit’s remote works.

A remote control for a mini-split
A remote control for a mini-split

Advantage of Mini-Splits

The main advantage of a mini split is they are relatively cost-effective to install in a single room that would be otherwise impractical to connect to a home’s central HVAC system. They also allow the room they are in to be heated or called separately from the house, which is great for ADU or mother-in-law units. Mini-splits are also energy efficient, as they don’t use as much electricity as a central AC.

Disadvantages of Mini-Splits

While it is possible to connect multiple walls to one condenser, mini-splits are generally impractical for heating or cooling an entire house. The cost of installing multiple units throughout a home would far exceed the cost of a central unit. Another disadvantage is the system’s remote buttons tend to be small and can make the remote difficult to use.

The main disadvantage is that there are so many variables in manufacturers, and dates are not installed on the units. Some mini-split systems may not last as long as a central HVAC system. For these reasons, it is impossible to estimate the expected remaining useful life of a mini-split.


Like regular HVSC systems, it is important to maintain the units. Whereas central HVAC systems often have disposable filters, mini-splits often have washable and reusable filters. Regularly check the outdoor compressor unit for debris such as leaves, branches, or dirt buildup. Keep the area around the unit clear to ensure proper airflow. Annual checkups by a qualified HVAC tech are recommended to ensure proper refrigeration levels and to ensure the units run as smoothly as possible for longer life.

Book your home inspection by calling 818-298-3405 or book online here.