Self-contained units are typically the best choice for smaller boats, up to about 40 feet (12m), due to the lower cost of the units and installation. A self-contained air conditioner has all of the major components mounted on a single chassis which is installed in the living area, usually under a bunk or settee or in a locker. Cooling-only models as well as reverse-cycle heat pump units are available. All reverse cycle units can operate in seawater temperatures of 5° Centigrade and above.

A single unit can cool each cabin, or can be ducted to 2 or more cabins to save space and cost. A self-contained unit is larger than a remote or tempered water air handler, so the space requirement should be considered and, even though the compressor in a self-contained unit is very quiet, it will be louder than an air handler. Good installation practices can reduce the emitted noise to a level acceptable by most. Self-contained units often require less power than other systems due to the highly efficient rotary compressors.