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Proper speed to run window A/C fan

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Using a window air conditioner can lower your central air-conditioning costs. Running it allows you to set your central air thermostat higher while keeping the most frequently used room or two cool and comfortable. Each degree you raise the central thermostat setting will save from 2% to 3% per degree.

When using a window air conditioner, the proper setting for the fan speed depends on the weather conditions in your area. In humid climates, set the window air conditioner fan speed to low or medium. This make it run longer and super cools the room air circulating through it. By super cooling the room air, more moisture is condensed out of it.

In hot dry climates, set the fan speed to high. This provides the greatest energy efficiency by blowing more room air over the cold evaporator coils. The air does not get super cooled because it is moving through so fast, but it gets plenty cool to make you feel comfortable.