Skip to Content

Thermostat Auto vs. On – Which Is Right for You?

Should your thermostat be set to auto or on? That’s a question many people ask, but few know the answer to. If you’re in the same boat, you’re in the right place.

Your air conditioner’s fan is what pulls air into the system so that it can be climatized based on your thermostat settings. Most modern systems allow you to set your AC fan to either auto or on with thermostat settings.

The bottom line is that both can work. It’s a matter of personal preference. You can even use both settings at different times of the day. We’ll dive into how you might want to do that and provide additional information on this topic in the sections below.

When the fan is set to “On”

The “On” setting tells your fan to run constantly without stopping until you change the settings again. As long as your fan is set to on, you’ll always feel airflow when you put your hand up to a vent.

The air that you feel can be either cool or warm based on what you’re doing with your HVAC system at that moment. It could even feel neutral if you’re not using any heating or cooling.

Thermostat auto vs. on – the pros of “On”

There are a few big reasons why leaving your fan set to “on” could be the right decision for your family.

  • One is that it provides an even distribution of airflow throughout your home. Fans help to push warm or cool air farther away from the vent that they exit. It keeps this air circulating to distribute climatized air through your home in a uniform manner. So this could be a good option if you constantly have hot or cold spots in your home.
  • You also get superior air filtration when you leave your fan on. This is because the fan is constantly re-passing the air in your home through an air filter. So it should help to remove more of the dust and allergens from the air that you breathe in your home.
  • Leaving your fan on will also help you cool down temperatures inside your home. These are similar to ceiling fans in that both promote better airflow, which helps to keep the air from stagnating and getting too hot.
  • Finally, you may even put less stress on the fan if you leave it on consistently. Having to start and stop constantly can put extra wear and tear on the fan that could reduce its lifespan.

Thermostat auto vs. on – the cons of “On”

There are also some pretty big reasons why you wouldn’t want to leave your fan on all of the time.

  • Perhaps the biggest is that it costs more. Your AC system will need more energy to power your fan 24/7. The exact increase in energy consumption will depend on your system’s efficiency. But it’s not uncommon to spend an extra $60 per month on this.
  • If your fan is always on, you’ll also have to replace your air filter more consistently. That’s because the filter is going to capture more of the dust from your home, and that can add up over time.
  • Leaving your fan on will also make your home colder in the winter. It creates a chilling wind feel in your home that may make you feel like you need to put on an extra layer.

When the fan is set to “Auto”

When your fan is set to “auto,” it will only run when your HVAC unit is cycling. In other words, a cooling or heating cycle will start, and your fan will kick on soon after. Then it will turn off automatically when the heating or cooling cycle is finished.

That means you’re only going to feel airflow coming from your vents when your HVAC system is cycling. You won’t feel any air movement whatsoever when it’s not.

Thermostat auto vs. on – the pros of “Auto”

  • Perhaps the most significant benefit of leaving your fan on auto is that it will use less energy. This is because the fan won’t have to use energy to run 24/7. It will only use up energy when it needs to.
  • You can also expect your air filters to last longer when you leave your fan on this setting. That means fewer clogs and fewer trips to the hardware store to pick up a new filter.
  • Finally, you’ll get superior dehumidification in your home during summer. That’s because it gives the moisture on your cooling coils the chance to drain outside. When your fan is always on, your system won’t get this opportunity. That ends up meaning more moisture being sent back into your home’s air.

Thermostat auto vs. on – the cons of “Auto”

  • A major con is that you won’t get any air circulation in-between HVAC cycles. That could make your home’s air feel static, stuffy, and stagnant in some places.
  • Additionally, your fan may wear out faster when you use this setting. When the fan is constantly having to start and stop, it puts more wear and tear on the part.
  • Finally, you’ll get less air filtration when using this setting. The air in your home won’t constantly pass through your HVAC system’s filter. And that means there could be more dust, pollen, and other allergens in your home’s air supply.

Thermostat settings – auto or on

Now that we know the difference between thermostat auto vs. on, let’s figure out which is right for your family.

Generally, the best option is to use both settings at different times.

For example, during the hot summer months, when you want extra air circulation to keep things from getting stagnant, on will be a better option. The same is true if you’ve got a lot of dust and pollen in your home that you want to filter out.

But it also makes sense to keep the fan on auto when you’re not home. That way, you’re not spending the extra money to increase your home’s air flow when nobody will be there to enjoy it.

You’ll also likely have your own goals and preferences that dictate how you use these two settings.

For example, maybe your air conditioner is old, and you want to make sure it lasts. That could be a reason to leave the fan on so that it doesn’t get extra wear and tear from constantly cycling on and off.

Potential alternatives

It’s also worth pointing out that you may have some alternatives to simply choosing between thermostat settings for auto and on. Here are two that could apply to your situation.

Smart thermostat circulation options

If you’ve got a smart thermostat, then your system may have a setting called “circulate.” You can think of this as a middle ground between on and auto.

It’ll run your fan during normal heating and cooling cycles like it would if you had set your thermostat to “auto.” But it will also run the fan a few extra times every hour to increase airflow.

For example, there are some new Honeywell programmable thermostats that use this setting to run the fan about 35% of the time. You’ll get some extra cooling and airflow in your home without having to leave the fan turned on all day and night.

Variable-speed air handler

You may also want to look into installing an air conditioning system that has a variable speed air handler. This allows you to run your fan 24/7 but gives you the ability to change the speed of the fan while you do.

This gives you some extra control that you don’t have with a standard HVAC fan. It could be a good fit for your home if you’ve ever been annoyed at how powerful or weak your fan is when it’s running.

These work by using a special motor that controls the speed of the fan. It typically allows you to choose between 30% and 100% capacity while adjusting to make sure you still maintain the desired temperature in your home.

The cool thing about these systems is that they can usually keep your home at the desired temperature at a lower, more energy-efficient fan speed. So you might be able to cool your home with one of these without getting skyrocketing energy bills by doing so.

Michael Joseph