Air conditioning was first introduced in the mid-20th century. This was a time of new prosperity for the United States. The advent of air conditioning changed how people lived and worked. It allowed Americans to work from home during the summer and in a hot climate. Early advertisements for air conditioning promised heightened productivity and increased comfort.
In the early 1900s, American railways installed small air-conditioning units in their trains. By the 1950s, air-conditioning systems became compact and practical for single rooms. Since then, air-conditioning has become more common, even in developed regions outside the United States. Air conditioning is now found in many residential and commercial buildings across the world.
A basic air conditioning system utilizes a cooling compressor that is located outside. Air from the compressor travels through a coil filled with refrigerant. A fan then blows this cooled air out. The cooled air is then circulated throughout the building by ducts, where it registers warm air and transports it back to the air conditioning system.
While air conditioning was originally developed to cool factories and improve productivity, it has become a necessity in American homes and automobiles. While humans have been cooling themselves for centuries through natural ventilation and fans, air conditioning is now essential to life in hot climates. The cost of air conditioning is significant, however. It consumes about 6% of the total electricity produced in the United States.