An air conditioner cools your home with a cold indoor coil called the evaporator. The condenser, a hot outdoor coil, releases the collected heat outside. The evaporator and condenser coils are serpentine tubing surrounded by aluminum fins.

What's the story of the modern air conditioners we're familiar with? Since 1947, AC units became more compact and cheaper. In that year, 43,000 systems were in use. By the 1960s, most new homes in the United States were built with central air conditioning.

What is an AC Unit? AC or air conditioning is a system designed to cool the air in your home. Some contractors or builders call an AC unit anything that conditions the air, hot or cold.

A fan blows indoor air across the cold evaporator coil where the heat inside the home is absorbed into the refrigerant. The cooled air is then circulated throughout the home while the heated evaporated gas is sent back outside to the compressor.