Mini-split ductless systems are composed of three main parts—an indoor air-handling unit, an outdoor compressor/ condenser unit, and a remote control that operates the system. A smartphone or computer can also control some units. Heat is transferred using refrigerant expansion and compression, in much the same way as a refrigerator works. During the colder months, heat pumps move heat from the cool outdoors into the warm house, and during the warmer months, heat pumps move heat from the cool house into the warm outdoors. They move heat rather than generate heat, so they can provide up to four times the amount of energy they consume. One outdoor condensing unit can be used for up to eight indoor air handlers in different zones of the house, each controlled to meet the needs of certain rooms. The number of heat pumps required will depend on the size of the home and how well insulated it is.
Each of the zones will have its own thermostat so only the occupied rooms can be conditioned, saving energy and money. Some units are self-correcting, so they can increase or decrease output depending on the set temperature.
These systems are also small in size, cost less to install than traditional HVAC systems, and use a fraction of the energy, substantially reducing utility bills. ENERGY STAR qualified systems can reduce cooling and heating costs by 30%. Newer models are continuously coming on the market that are increasingly efficient.