Today, ductless "mini-split" heat pumps provide homeowners and contractors with a permanent HVAC system option that is well-suited to retrofit applications. Unlike a conventional forced-air system that relies on a network of ducts and a large, centrally located air handler, a ductless system includes smaller air handlers that are permanently mounted on the wall or ceiling. Each air handler is supplied with electricity, a refrigerant line connected to an outdoor compressor, and a condensate drain line.

The unit typically has remote as well as console controls and blows conditioned air into the room. Depending on its size, a single exterior compressor unit can supply one or more room-size air handlers, and each air handler can be controlled independently. Most mini-split systems are designed as a heating and cooling system. As with other heat pumps, the heating mode doesn't work efficiently when temperatures are below freezing.