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Should Your Thermostat Fan Be ON or AUTO?

This summer – whether you have a manual or smart thermostat  from ClimateCare in your home – chances are you’ve wondered whether the air conditioner fan should be set to ON or AUTO.

It’s a common question many homeowners have.

After all, some people swear by the ON setting, while others are convinced AUTO is the way to go.

In order to properly answer the question of should the thermostat fan be ON or AUTO, you first need to know the differences between each setting.

What is the ON setting?

Thermostat fan setting on

In short, ON means on. The fan is constantly blowing.

Some furnaces come with a constant low speed setting when the thermostat is set in the ON position.


  • You’ll want to use the ON setting when you would like to keep the air in the home consistent. Perhaps you want the cooler air in the basement and the hotter air in the upstairs bedrooms to be more balanced. A constant fan can help with this.
  • Air is always flowing through your home’s air filtration system, which will ensure your indoor air is clean if you have a decently efficient filter and keep your windows closed.
  • With your thermostat set to ON, there will be fewer stop-and-start cycles for your AC fan which can help extend its lifespan.


  • The fan always running can lead to somewhat higher energy bills.
  • You’ll may be changing your HVAC filters more often.
  • Because the fan is always running, it could experience malfunction more often.

What is the AUTO setting?

AC fan auto

AUTO is short for automatic. The fan only turns on when cooling or heating is required.

If you are generally as comfortable in one room of your home as the next, you’ll want to use the AUTO setting. The AC fan kicks in when needed and stops running when the job is done.


  • Saves energy and lowers your monthly energy bills.
  • Air filters may not need to be replaced as often.
  • Greater control over your system. You specify when the fan turns on (by temperature) and when it shuts off.


  • Conditioned air isn’t delivered evenly through your home, which can result in hot-and-cold spots.
  • The indoor air quality in your home may not be as clean and clear as it would in the ON setting.

Thermostat fan ON or AUTO. What’s right for you?


Your thermostat fan setting controls your HVAC system’s blower. The blower helps circulate cold or hot air throughout your home until the temperature reaches the thermostat setting.

ON means that the fan is constantly blowing, even when the desired temperature has been reached.

So what’s best for you?

It all comes down to the needs of you and your family.

For example:

  • If you have allergy sufferers in your home, you might want to have the consistent air circulation of the ON setting.
  • On the other hand, if you’re looking to cut down on your monthly hydro bills, the AUTO setting is your best option.
  • Do elderly relatives or parents live with you? The ON setting will keep them comfortable and safe, especially during a heatwave.

Need more info? Looking for advice? Contact your local ClimateCare member

This summer is going to be hot That means your air conditioner will be working overtime to keep your family cool.

You want to make sure it runs efficiently and reliably with regular air conditioner maintenance.

After all, you don’t want it breaking down on the hottest day of the year.

Whether you want to schedule a service call, have questions about ON or AUTO, or want to upgrade your current AC, ClimateCare can help.

Find the nearest ClimateCare location to you in Ontario & Greater Toronto Area.