Read Time: 4 minutes
Your HVAC fan setting plays a bigger role in your home’s comfort and energy use than you might realize. Most thermostats offer two main settings — “On” and “Auto.” Both options have their benefits, and the right choice often depends on your comfort preferences, your home’s layout, and even the type of HVAC system you have.
Let’s break down the pros and cons of each so you can make an informed decision for your home.
Pros of Leaving the Fan ON
- Improved Air Circulation
Keeping your HVAC fan running constantly helps move air throughout your home, reducing hot and cold spots and creating more consistent comfort.
Think of it like cruise control: smooth, steady, and balanced airflow that keeps your whole home feeling even.
- Better Air Filtration
With the fan always running, your HVAC air filter continuously captures dust, pet dander, and allergens. This can make a noticeable difference for households with allergies, asthma, or pets that shed.
- Comfort During Shoulder Seasons
When the weather is mild and you’re not actively heating or cooling, running the fan can help circulate fresh air and prevent your home from feeling stale. It’s a small comfort boost between the major heating and cooling seasons.
Cons of Leaving the Fan ON
- Higher Energy Use
A fan that runs 24/7 consumes electricity continuously. Depending on your system, that can lead to higher monthly energy bills, especially if you have an older single-speed blower motor.
- Increased Wear and Tear
Since the fan is always running, parts like the blower motor may wear out faster over time compared to when they cycle on and off only as needed.
- Humidity Concerns in Summer
In cooling mode, the air conditioner removes moisture from your indoor air. If the fan keeps running after the cooling cycle ends, it can blow some of that moisture back into your home — making it feel more humid than it should.
Pros of Leaving the Fan on AUTO
- 1. Energy Savings
When your fan runs only during heating or cooling cycles, it uses less electricity, which can reduce your energy bills.
- Less Wear on the Motor
Since the fan isn’t running constantly, it experiences less mechanical stress. This can help extend the lifespan of your blower motor and reduce the need for repairs.
Again, the type of motor matters here — ECM motors are more efficient and durable than older single-speed models.
- Better Humidity Control
In cooling mode, the fan shuts off when the air conditioner does. That means moisture removed from the air during cooling stays in the drain pan instead of being blown back into your home. This helps maintain lower indoor humidity levels, especially important in Utah’s warmer months.
Cons of AUTO Setting
- Less Air Filtration
Because the fan only runs part of the time, your air filter doesn’t capture as many airborne particles. Over time, this can slightly reduce indoor air quality, especially in homes with pets or dust issues.
- Uneven Temperatures
When the fan stops running, air circulation also stops. That can lead to temperature variations from room to room — like a warm upstairs and cool basement.
So, Which Setting Is Better?
There’s no one-size-fits-all answer. It depends on what matters most to you:
- For energy savings: Go with Auto.
- For air quality and consistent comfort: Try On (especially if you have a high-efficiency variable-speed motor).
If you’re unsure, test both settings for a few days each and see which feels better in your home. Or, ask an HVAC professional to check what kind of fan motor your system uses — that can make all the difference in efficiency and performance.
