An air conditioner's exterior-facing portion contains a compressor, fan, and condenser, while the part that faces a home's interior contains a fan and an evaporator. Most room models are designed to fit double-hung windows, though some are built for casement and slider windows and others for in-wall installation.
Most models have adjustable vertical and horizontal louvers to direct airflow. Many offer a fresh-air intake or exhaust setting for ventilation, although this feature moves a relatively small amount of air. An energy-saver setting on many units stops the fan when the compressor cycles off. Electronic controls and digital temperature readouts are also common. A timer lets you program the unit to switch on (say, half an hour before you get home) or off at a given time. Many models also include a remote control. Some models install with a slide-out chassis--an outer cabinet that anchors in the window, into which you slide the unit.
