Air conditioning
Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1902 by US inventor Willis Carrier. The introduction of residential air conditioning in the 1920s helped enable the great migration to the Sun Belt in the United States.
Packaged terminal air conditioner
Although PTACs are used mostly to heat or cool a single living space using only electricity (with resistive and/or heat pump heating), there are cooling-only PTACs with external heating through a hydronic heating coil or natural gas heating. Typical PTAC heating and cooling capacity values range from 2 to 5.5 kilowatts (7,000–19,000 BTU/h) nominal. One characteristic of PTACs is that condensate drain piping is not required because the condensate water extracted from the air by the evaporator coil is drawn by the condenser fan onto the condenser coil surface where it evaporates. Conventional PTACs still require condensate drain piping to be installed. The first practical semi-portable air conditioning unit was invented by engineers at Chrysler Motors and offered for sale starting in 1935.