As mentioned previously, there are two basic types of air conditioners¨Croom air conditioners and central air conditioners. However, there are several different kinds within each type. Variations of room air conditioners are as follows:

Window-mounted types are available for installation in single-and double-hung windows, as well as for horizontal sliding windows and even casement windows.
Wall-mounted units use a sleeve to allow for through-the-wall mounting instead of window mounting.
Free-standing portable units are easily moved on casters; some require temporary ducting to the outdoors.

Variations of central air conditioners are as follows:

A single-package unit contains all the components and generally mounts through the wall or on the roof. Ducting to and from the unit conveys air to and from the rooms. This type is not commonly used in residential applications.
A split-system unit consists of indoor and outdoor sections. The indoor heat exchanger, or coil, mounts above the furnace, inside the ducting. The outdoor section consists of the remaining components, and the two sections are joined by refrigerant lines connecting the indoor coil to the refrigeration components in the outdoor section.
A mini-split unit is similar to a split-system but contains more than one indoor coil connected to one outdoor unit. Some mini-split units have as many as three indoor units. These units are ideal for homes with new additions, as there is no need for ductwork. The indoor section simply mounts on an inside wall, the ceiling or the floor. The outdoor and indoor units generally have a very slim profile compared to conventional split-systems. The efficiency of mini-split units tends to be lower than other split-systems, which needs to be taken into account when considering such a unit.
A mini-duct unit is a central air conditioner where the indoor section is installed in the attic, and air is distributed through plastic pipes in partition walls to outlets and inlets. These units can be retrofitted in homes with electric or hydronic baseboard heating that have no ductwork.
Finally, water-cooled residential air conditioners can be connected to city or well water. Check with local authorities to determine if water-cooled equipment is permitted. These types are seldom used in Canadian applications, even if permitted, because operating costs would include electricity, as well as water and sewer charges.

The remaining sections provide more information on the two basic types of air conditioners.