A mini-split AC unit

Air Conditioning Systems Compared: Part I

Most people only know a few things about their air conditioner: it cools the house, you don’t want it to break, and you don’t leave the windows open when you run it. But you should also know what basic type of system you have, as that might affect how to take care of it and how to maximize efficiency, and telling a technician before they arrive might save some time. So in this post and in Part II, let’s talk about the main types of systems.

Standard split system

A split system is probably the most common type in most American homes. The “split” is between an outdoor unit and an indoor unit. The outdoor unit has coils to disperse heat and the indoor coils send cold air through a blower, also called air handler. The two units transfer heat via refrigerant lines. A standard split system has only one indoor unit which sends cool air through ductwork to all the rooms in the building.

The upsides:

The downsides:

  • Ductwork can reduce system efficiency a lot if not properly designed and insulated.
  • Multiple vents and ducts mean need to install and regularly replace more air filters.


Also known as ductless split systems, these air conditioners have an indoor and outdoor unit behaving basically the same way as in a standard split system, except without ductwork. When some techs speak of “split systems” they sometimes mean these specifically. Instead, there is a separate indoor unit in each room, connected with the outdoor unit. The indoor units transfer heat to the outdoor unit with the same refrigerant lines as a standard system, and there are no ducts because each air handler is separate. Each unit is a lot less expensive than a central system with ducts, but the cost would add up if you put one system in each room of your house. They are better suited to small buildings, or to parts of a house like a sunroom/enclosed patio that does not have ducting.

Window and wall units

These units contain all the system components of an air conditioner in one unit – the compressor, condenser, expansion valve, etc. Window units fit into your window and are probably the least expensive system out there. No need to install ducts or refrigerant lines in your home. Wall units are likewise all-in-on, but they require making a hole in the wall for installation and sealing it up afterward. Wall units are mostly found in motels with indoor hallways instead of catwalks.

The upsides:

  • Compact and has simple wiring, typically just a standard plug
  • Low maintenance, mostly just cleaning the filter
  • Window units have easy installation
  • Lower cost than most systems

The downsides:

  • Each unit only works for about one room
  • Noisier than central duct or ductless split systems
  • Some older models are less energy efficient
  • Window units on the first floor have to be secured against burglars
  • Can reduce view from the window

We’ll cover more air conditioning systems in Part II, but if you have any specific questions about how different systems stack up against each other or how to find the best one for your space, give Twin Air in Manassas a call at (703) 754-1062 or email us on our website.

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