Quite simply, when you turn the thermostat on an air conditioning unit up or down 1° C, you are jumping farther up or farther down than you would be on the Fahrenheit scale. 20° C is about 68° F. Initially, I was extremely comfortable with this temperature on our first night in the hotel, but throughout the course of the night, it felt too cold, and my wife was freezing. I decided to turn it up to 21° C. I did the conversion real quick in a web browser and found that it was now 69.8° F! Still, my wife complained that it was too cold. Once again, I turned up the temperature 1° C and looked and saw that was the equivalent of 71.6° F. So ultimately, a 2° difference in Celsius meant a 3.6° difference in Fahrenheit. So, I was left with the impression that Fahrenheit is simply better for HVAC systems than Celsius. Fahrenheit ultimately gives you more control over the temperature in a room.