From Buildings to Single Rooms
By the late 1920s, air conditioning was well established in theaters, department stores and large offices, but it relied on big central plants. Cooling a single room or apartment with a compact machine was a different challenge. A home unit had to be small enough to be installed by non-specialists, quiet enough to live with, and cheap enough for a family. The first of these requirements was hard to satisfy with equipment of the era, and the others took longer still.
Early Experiments in the 1930s
Several inventors and companies worked on room coolers in the early 1930s. One frequently cited example is the window-mounted unit patented in 1931 by H. H. Schultz and J. Q. Sherman. It was designed to sit on a windowsill, but it was heavy and expensive, and it did not reach the market in any meaningful numbers. Around the same period, Carrier, General Electric and other firms built self-contained cabinets and “weathermaker” style systems for homes. These were mostly sold to wealthy customers or installed in a few demonstration houses.
Several factors held back the early units:
- Compressors and motors were large, and the refrigerants of the day were not ideal for compact use.
- Few homes were wired for the electrical load, since a cooling unit needed more current than lights and radios.
- The Great Depression reduced demand for costly luxuries.
- During World War II, manufacturers’ attention and materials moved to war production.
For these reasons, home air conditioning remained a curiosity until the late 1940s.
The Postwar Window Unit
After the war, conditions changed. Factories had capacity, wages were rising, and many homes in the United States were being built or wired for appliances. Manufacturers introduced window units that used a sealed compressor, a condenser and a fan in a single box, with the hot side facing outdoors and the cool side facing the room. The design was a close relative of the household refrigerator, which had already shown that sealed systems could be reliable. Because both machines draw on the same cycle, the research on sealed compressors and refrigerants for refrigerators was directly useful.
Sales rose steeply through the late 1940s and 1950s, from small numbers to hundreds of thousands and then more per year, though the precise figures depend on the source and are not given here. Window units were popular because they were affordable compared with central systems, could be installed in an existing house, and could cool only the rooms that were being used, such as a bedroom. Many buyers started with one unit and added more over time.
Making Them Practical
Several engineering changes made window units appealing:
- Lighter and more efficient compressors reduced weight and noise.
- Slide-in mounting brackets allowed owners to install units in double-hung windows.
- Adjustable thermostats and fan speed controls gave users a measure of control over comfort.
- Condensate drainage was improved so that water dripped outside.
Electrical wiring was another practical issue. Early units often overloaded household circuits, and builders gradually added dedicated outlets. The growth of electric kitchen appliances in the same years put additional demands on home wiring.
Central Systems and Other Types
By the 1960s and 1970s, central air conditioning had become common in new houses in many parts of North America, using ducts and a single outdoor condenser. Window units continued to fill the gap in older homes and apartments. In Japan and elsewhere, manufacturers developed ductless split systems in the 1950s and 1960s, with an outdoor unit linked to an indoor wall unit by refrigerant lines. These designs became widespread in many countries because they suit buildings without ductwork.
Portable units, through-the-wall sleeves and, more recently, inverter-driven units that adjust compressor speed to match demand continued the trend toward flexibility and efficiency.
Social Effects in the Home
Having a cool room changed how people used their homes. Families moved sleeping, working and watching television into the cooled room during heat waves. The porch declined as a summer gathering place, and house designs adapted to sealed windows. The effects of this change at the scale of cities and regions are covered under the cooling revolution, while the wider story of how people experience indoor spaces is part of the indoor climate theme.
There were also new costs, such as higher electric bills and, in dense areas, more waste heat released outdoors. As with other household machines, modern units are much more efficient than early ones, but exact comparisons depend on the model and standard used.
Why It Took So Long
Looking back, the home air conditioner was possible technically in the early 1930s, yet it needed cheaper compressors, safer refrigerants, wired homes and rising incomes to become a mass product. That pattern is common in the history of inventions: the idea arrives first, and the supporting conditions follow years later.