Systems were originally developed in Japan where a space saving and energy efficient option was required for heating and cooling homes. They work in similar ways to the traditional central air conditioner or heat pump. They do not take up any floor space for a fan coil or furnace, the fan motor is smaller and produces less noise, and there are no air ducts, so the system typically costs less to install. They can be a good choice for residential, commercial, and institutional buildings.
Ductless AC systems are typically controlled through a remote to set the temperature, change the modes of operation, and set timers. More advanced units include a temperature sensor in the remote. Some units can connect to more than one indoor fan coil unit. These are called multi-split units and can save money when more than one ductless unit is required.
They are of small size and have flexibility for heating and or cooling individual rooms. Some models can have as many as four indoor air handling units (four zones/rooms) connected to one outdoor unit. Each zone can have its own thermostat, so you are only utilizing a “zone” when occupied, which saves money and energy. There is a 30% loss of energy consumption in duct work of traditional central air conditioning versus no ducts, especially if the ducts are in an attic. They can be suspended from a ceiling, mounted on a drop ceiling, or hung on a wall.