On a hot day and traveling in a car, which method of keeping the occupants comfortable with the A/C is more energy and fuel efficient?
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Set the thermostat to a lower temperature and keep fan speed to the lowest setting
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Set the thermostat to a slightly higher temperature and compensate by setting the fan to a higher speed so you can feel cool enough with the breeze
I think the more energy efficient will be the second option since you’re not cooling to as low of a temperature. The fan speed change doesn’t seem likely to be a big energy difference, but not having to cool as much is likely to save significant energy.