The significant change in air conditioning after 1945 was the widespread adoption of window units. Following World War II, technological advancements, increased manufacturing capabilities, and economic factors led to the development and popularization of window air conditioning units. These compact systems made air conditioning more accessible to the general public, allowing individuals to cool specific rooms rather than requiring entire building-wide systems. This shift transformed the market and habits of consumers, making air conditioning a common amenity in homes and improving indoor comfort during hot weather.
The introduction of central air systems and the invention of portable air conditioners did occur around this time, but they did not have the same immediate impact on the average consumer as window units did. Additionally, the removal of freon in cooling systems is a more recent development related to environmental concerns and not a significant change immediately following 1945. Therefore, the widespread adoption of window units stands out as the key change in air conditioning during that era.