From the window air conditioning units of the 1970s, manufacturers have gradually developed the ductless systems of today.
The primary goal of the pioneers in developing the ductless system was to provide air conditioning localized to specific areas in homes and buildings when a system to manage the entire building was not feasible due to space or financial limitations. As these units were developed, they eventually began addressing heating as well as cooling. Thus the evolution of ductless heating and cooling.