Does Running the HVAC Fan Continuously Help Cool Your Home?

Many thermostats give homeowners two basic choices for operating the HVAC fan: AUTO or ON. Some smart thermostats also include a circulation mode that runs the fan periodically throughout the day.

So which setting is best? Does running the fan continuously help cool your home, or does it simply use more electricity?

The answer depends on what you're trying to accomplish. While running the fan can improve air circulation in some situations, it doesn't actually increase your air conditioner's cooling capacity.

What Does the HVAC Fan Do?

The blower fan's job is to move air through your home's ductwork. When the air conditioner is running, it pushes cooled air into each room. When the heating system is operating, it distributes warm air throughout the home.

The fan itself doesn't cool the air. That's the job of the outdoor unit and the indoor evaporator coil. Running only the fan simply redistributes the air that's already inside your home.

What Happens When the Fan Is Set to AUTO?

When the thermostat is set to AUTO, the blower runs only when the heating or cooling system needs it. This is the setting most HVAC systems are designed to operate with, and it's generally the most efficient choice for everyday operation.

Many newer smart thermostats also include a circulation feature that provides a middle ground between AUTO and ON. Instead of running the fan continuously, these thermostats may circulate air for a set number of minutes each hour to help even out temperatures while using less electricity than leaving the fan on all day.

When Running the Fan Can Be Helpful

Continuous or scheduled air circulation may help:

• Reduce temperature differences between rooms
• Keep air moving in areas that tend to feel stuffy
• Move more air through your HVAC filter
• Improve the effectiveness of whole-home air cleaners or other indoor air quality equipment

While these benefits can make your home feel more comfortable or improve indoor air quality, they don't increase the amount of cooling your air conditioner produces.

What Are the Downsides to Leaving the Fan On?

The biggest drawback to running the fan continuously is increased electricity use. While the blower motor uses much less energy than the outdoor air conditioning unit, running it around the clock still increases your home's energy consumption and may produce more background noise than many homeowners prefer.

Running the fan continuously can also make humidity control slightly less effective in some homes. After an air conditioning cycle ends, moisture remains on the evaporator coil until it drains away. If the blower continues running, a small amount of that moisture may evaporate back into the air. The effect is usually modest, but in homes that already struggle with indoor humidity, leaving the fan on continuously can make it a little more difficult to maintain comfortable indoor humidity levels.

Which Setting Is Best?

For most homeowners, AUTO is the best everyday setting. It allows the HVAC system to operate as designed while minimizing unnecessary electricity use.

If your home has uneven temperatures or you'd like more consistent air circulation, a thermostat with a circulation mode may provide a good compromise by periodically running the fan without leaving it on continuously.

If you're unsure which options your thermostat offers, your HVAC technician can help you determine the settings that best match your equipment and comfort goals.

Will a New Air Conditioner or Heat Pump Improve Your Home’s Comfort?

If some rooms never seem to reach the same temperature as the rest of the house, or you’re looking for a better air filtration solution, leaving your blower fan on 24/7 may not be the ideal answer. The HVAC experts at Tom's Mechanical can evaluate your AC or heat pump, identify airflow issues, check your thermostat settings and recommend solutions to help improve comfort and indoor air quality throughout your Arlington home.

Call us at 817-277-4493 to request service or a free AC replacement estimate.