There is so much more that goes into today’s heating and air conditioning systems than what there was 100 years ago, then people seem to take for granted the heating and air conditioning systems of today… You turned the oil furnace on, had a quick inspection done by an actual heating and air conditioning specialist, made sure you had enough fuel in the tank, and heat came out of the ductwork.
The a/c unit is cleaned, coolant levels get inspected and filled, and then you turn the a/c on.
You choose a temperature on the temperature control, and the home’s temperature can be the same year round, regardless of the weather. The heating and air conditioning specialist does most of the work, even if the homeowner does need to change the air filters. I remember our father telling me how they would go to the island and occasion up coal for their oil furnace. There were only multiple or six when they were working. When their buckets were full, they would carry them back home. His father inspected the fire multiple times in the afternoon, so they would have heat all winter long. During the summer, his mother would hang wet curtains up to the window. As the slightest breeze came through the open window, the wet curtains would dry, however cool the hot breeze. This was his a/c. He told me years ago, someday guys would undoubtedly not need to do too much to check the heating and air conditioning systems. They would all be automated and run by laptops. I have now lived long enough to have automated, integrated laptop systems that run heating and air conditioning systems, and entire buildings. It takes one guy to tend the laptop, and if any work needs to be done to make repairs, they are only a phone call away.