Furnace Fan Setting “On” or “Auto”?

by | Feb 27, 2018 | Heating

Setting a Furnace to on or auto in salem Oregon

On your thermostat, there’s a furnace-fan setting for either “On” or “Auto.” Which option is the best choice? There are devotees of both settings, each believing their setting is the optimum one to choose. But in reality, it’s more of a pros-and-cons type of situation. It really depends on which benefits are a priority for you. If you need help making the decision, call Gagles Heating in Salem OR and talk to one of our knowledgeable technicians.

What’s The Difference

If you have your thermostat’s furnace (or air-conditioning, for that matter) fan set to “On,” the fan will continually run, regardless if your furnace is running through a heating cycle, i.e., whenever your furnace is actually producing heat. If you have your furnace (again, or air-conditioning) fan set to “Auto,” your system’s fan will run during the furnace’s heating cycle only. When your system reaches the temperature you’ve set for it, the fan will shut off until the next cycle.


“On” option––Air is always being cycled through your furnace filtration system when your fan is continually running. The result is better air quality, since particles are constantly being removed from your air. Keeping the fan running also means heating is more evenly distributed throughout your home. No pockets of hot and cold. This also improves the reliability and life span of your system due to decreased starts and stops, somewhat like a car with highway or city driving. Less wear and tear.

“Auto” option––Since the fan only runs when the system tells it to and at the slowest speed necessary for heating, it’s consuming less energy than the “On” option. This translates to decreased energy costs and less money spent by you. Your furnace filter will also last longer, since air isn’t being pushed through it as much.


“On” option––The biggest con to having your fan continually running is the cost involved. It’s going to be expensive (unless you have a variable speed motor), much more than it would be on the “Auto” option. Another downside is you’re going to be replacing your furnace filter more frequently, since your air is being continually cleaned. Also, in the winter, you may feel a little cold from time to time. Since the fan is running even when the furnace isn’t running through a heat cycle, cold air will be blowing through your vents during that time.

“Auto” option––With this option, since there are more starts and stops, there will be more wear and tear on the furnace. With all these starts and stops, there’s also less even distribution of heat. Once the furnace stops, the air is no longer being moved around, resulting in cold spots. Also, since your air isn’t being filtrated 24/7, your house air isn’t as clean.

As you can see, it’s definitely not a clear-cut case of which is better. It’s a matter of what’s better for you here in Salem Oregon. If you would like to discuss these options in more detail, call Gagles Heating, and one of our expert technicians can answer any of your questions.

Gagles Heating is proud to be located in Salem Oregon and serve all of the surrounding communities. We provide trustworthy and reliable plumbing and service and repair on all furnace, air conditioning and HVAC systems. If you are not sure if you are in our service area, call our office today or check out our service area page for more information.

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