In 1931 H.H. Schultz and J.Q. Sherman invented the first window ledge air conditioning unit. It was meant to cool a single room or small living space, and are still used today. They of course were only available to the wealthy, and cost around $150,000 in today’s money.
In 1942 the United States had to build its first “summer peaking” power plant. This was due to the popularity of air conditioning units. Power companies had to create enough electricity to support the high draw by consumer units in the summer months.
In the 1950’s there was a large economic boom due to the end of World War II. This allowed more families the ability to purchase air conditioning units. By the end of 1953 more than a million units had been sold. They became a common modern household appliance.
In the 1970’s central air as most of us experience it today was developed. This unit is located outside of the home and ventilation ducts are piped throughout the entire home.
In 1994 Freon aka R-12 is found to be an ozone depleting refrigerant. Most brands manufactured their own environmentally friendly coolants. However the most common refrigerant used today is R134.