The three basic types of HVAC systems are split systems, packaged systems, and ductless mini-split systems. Split systems are the most common type of HVAC system and consist of an outdoor unit that houses the compressor and condenser, and an indoor unit that contains the evaporator. Packaged systems are all-in-one units that contain both the condenser and evaporator in one unit, and are typically used in smaller spaces. Lastly, ductless mini-split systems are similar to split systems, but do not require ductwork and are more energy efficient.