Should I Set My AC Fan to On or Auto? (2024)

Your AC unit is a critical piece of equipment that helps keep you from overheating, even when outdoor temperatures soar. Like any other investment, you want to get the most out of your AC and ensure you use it appropriately to maximize energy efficiency without sacrificing comfort.

One of the most common questions homeowners have when looking at their thermostat settings is: should the AC fan be on AUTO or ON? Keep reading to find out more about what these settings do and how to make this decision for your home:

  • What happens in AUTO mode?
  • What happens in ON mode?
  • Determining factors for choosing ON vs. AUTO mode

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What Happens in AUTO Mode?

Your AC’s AUTO setting ensures the fan only runs when the unit is actively cooling your home. This means the fan will kick on when the thermostat reads a temperature above the one set and will turn off once that temperature is reduced to your optimal level. This mode is considered more energy efficient but will also wear down your fan's motor quicker by repeatedly turning it on and off.

What Happens in ON Mode?

The ON mode keeps your AC's fan blowing constantly, even when cool air isn't being sent and regardless of the temperature inside your home. The fan will run continuously until you change the settings or switch the unit off. This mode offers more consistent air filtration but requires you to change your air filters more frequently.

Determining Factors for ON vs. AUTO Mode

So, what's the verdict between having your fan set to ON vs. AUTO? Should you leave your AC on AUTO to save energy? Well, that depends on several factors. While AUTO mode may seem like the best choice, there are times when having the fan on may be better. For most homeowners, understanding the pros and cons of both settings and switching between them for their strengths can offer the best of both worlds.

Comfort

Having your AC in ON mode means the fan will be blowing air all the time, mixing warm and cold air together. This creates more even cooling throughout your home, so you're less likely to encounter hot spots, and it keeps air moving against your skin, which can also have a cooling effect. In the winter, however, this setting can create the same sensation, possibly making it feel colder in your home than the reading on your thermostat. It also creates consistent background noise in your home. If you prefer to feel the air moving and like a little ambient noise to soothe you, it may make sense to keep the fan on.

Having your fan in AUTO mode offers a dehumidifying effect. Without constant air blowing to circulate water vapor throughout your home, the moisture can collect inside the air conditioner, allowing it to drain properly outside of your house. This can be helpful when outdoor humidity levels are high or if you've experienced dampness in your home. However, being in your home without air circulating can also cause discomfort. This is especially true if several people live with you or have pets in your home. Stale air can help odors linger and create a greater concentration of airborne irritants between fan cooling cycles.

Energy Efficiency

AUTO is significantly more energy efficient between the two modes since the fan is only running when your AC is going through its cooling cycle. This takes less power, which is more budget-friendly, with some estimates showing you can save as much as $50 per month just by keeping your AC on AUTO. This can also be helpful during extreme heat waves when the local electricity grid is experiencing an overload or even if you're just trying to be more energy conscious about doing your part for the planet.

Air Filtration

Having your AC set to AUTO will give you more time before changing your air filters because they're only being used during the cooling cycle. This means, however, that your air is not being filtered when your fan is off.

If you have people in your home who suffer from allergies, keeping your AC in the ON mode will remove more irritating particles from the air, offering them greater relief. If you're going through your home to do some deep cleaning, keeping your fan running will help remove all the pet dander and dust that tends to be kicked up into the air while you work. Keeping the air moving will also help distribute any odors from cleaning products you may be using, ensuring the air you breathe is less contaminated. This mode is also appropriate when you host a large indoor gathering since the circulating air will prevent the room from feeling stuffy with many people in close quarters. It also works during the milder spring and fall seasons when the temperatures are already comfortable, and you don't need help keeping your house cool.

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Should I Set My AC Fan to On or Auto? (2024)

FAQs

Should I Set My AC Fan to On or Auto? ›

Given the amount of money it costs in increased utility bills and filter purchases to keep your AC fan running constantly, most of the time, you'll want to keep the fan in the “auto” position.

Is it better to have AC fan on auto or full? ›

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. There is better dehumidification in your home during the summer months. When your fan is set to AUTO, moisture from cold cooling coils can drip and be drained outside.

Is it better to have the AC fan on auto or manual? ›

Compared to the ON setting, the AUTO setting gives you benefits such as: Lower energy consumption. In AUTO mode, the blower fan only runs when necessary, which cuts down your AC system's energy usage. Reduced wear and tear on AC components.

When AC is on, should the fan be on? ›

Answer: You can— and should— run your A/C and ceiling fan together. Doing so can help lower your cooling costs each month, but only if you're using them right.

Is it better to run your AC fan all the time? ›

Pros of Keeping Your Fan On

First, running fans contribute to even temperature distribution. This reduces the hot spots in your house. Hot spots occur when an area doesn't receive the same temperature-controlled air as other rooms. You'll also enjoy improved air quality in your home.

Is it OK to leave the AC fan on instead of on auto? ›

When your fan and air conditioner are running all the time, more electricity is produced. All in all, it is better to leave your air conditioner's fan on auto, instead of “On” at all times.

Is it cheaper to have fan on auto or on? ›

Since the AUTO setting means the fan is only engaged when the system is on, rather than constantly blowing, AUTO is the most energy-efficient option between the two settings. This means you'll be using less energy and saving money on your electric bill by using the AUTO setting.

Is it OK to keep AC on fan mode? ›

You can expect a more considerable maintenance burden if you run the fan continuously, even if you're running the AC fan without cooling. The filter will clog sooner, and the mechanical parts need more frequent attention to avoid breakdowns.

Which mode is best for AC in summer? ›

Dry mode is especially useful during humid seasons such as summertime, when you may find yourself fighting against high levels of humidity in your home. Eco or energy-saving mode: In case the name doesn't already give this one away, the eco-mode or energy-saving mode is designed to use less power.

When should I run my AC fan only? ›

Running the blower fan constantly in summer can pull more warm air into your home. As a result, you may need to run your AC system more frequently. But running the fan at night, when it's cooler, can reduce the demand. Since the fan will run only during certain hours, wear and tear may be less of a concern.

Can I leave my AC fan on all day? ›

Pros to Running Fan on Air Conditioner Continuously:

Less frequent starts and stops of the fan can reduce the stress from startup, and potentially help extend it's lifespan. Leaving the fan on 24/7 ensures cleaner air, as the air is pulled through the filtration or UV light system.

Is it expensive to run AC fan all day? ›

Therefore, the fan uses about 360 kWh per month in the ON mode. The average kWh in the US costs about $0.12 so it costs about $43 per month, or about $520 per year, to run a fan continuously.

Does leaving your AC fan on save money? ›

Saving money is one of the most obvious reasons to not keep the air conditioner fan on all the time. As you've probably guessed, when it's continuously in operation, it uses up a lot of energy. As a result, you could pay hundreds of dollars more in energy bills each year than you otherwise would.

Is it better to run the AC fan on high or low speed? ›

Increasing the fan speed enables more air to pass through the air conditioner. We recommend to set the fan speed at high levels at the start of cooling (or heating), when the room is much warmer (or cooler) than the set temperature. At night, the air conditioner can be set a lower level.

Is auto mode good for AC? ›

Auto mode is ideal for homeowners who want to maintain a consistent temperature in their homes without having to constantly adjust the settings. It's especially useful during the hot summer months when temperatures can be extreme. Program auto settings can maintain different temperatures throughout the day.

Is auto better than cool on AC? ›

Once it reaches the set temperature, it will turn off until the next cooling or heating cycle. The “AUTO” setting acts as a dehumidifier as it pulls moisture from the air in your home and allows it to drain and drip outside. The “ON” setting does not do this.

When to use fan mode in AC? ›

Running your AC in fan mode saves energy because your AC compressor will not have to work. Experts recommend you try this trick during cool weather when you don't need the temperature to decrease. You can also turn on the fan mode after your AC reaches your ideal air temperature.

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