The AC is a common source of debate in many households. Whether it's about finding the right temperature for maximum comfort or saving money on energy bills , people have some pretty strong opinions about the "right" way to use the AC. Some of the common settings on a typical central air thermostat can also cause confusion, like the difference between the "on" setting and the "auto" setting. So, we asked HVAC pros to clear things up and confirm the right setting to choose for maximum efficiency and efficacy—personal preferences and opinions aside.

For starters, the "Auto" and "On" settings on your unit or thermostat refer specifically to the fan inside your unit. "When the fan is set to 'on,' the fan is constantly running," explains Stewart Parnacott , PhD, owner of Varsity Zone HVA

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