How to set your air conditioning and furnace fan

Updated on March 19, 2024

3-minute read

How to set your air conditioning and furnace fan

Updated on March 19, 2024

3-minute read

Your furnace and air conditioning system help you control the temperature in your home. They also help circulate the indoor air, which keeps your heating and cooling consistent throughout the house. That is essential for keeping your home comfortable year-round!

Your heating and cooling system has a few fan settings. You can adjust them to improve energy efficiency and make sure you’re comfortable.

Woman on couch under portable air conditioner with remote in hand
Woman on couch under portable air conditioner with remote in hand
Woman on couch under portable air conditioner with remote in hand

Choosing “auto” or “on.”

Most furnace and air conditioning systems have two fan settings: "on" and "auto." The labels may not be super clear, so here is what each setting does:

  • Setting your HVAC fan to “on” will run the fan constantly. It will push air through the house whether the AC or furnace is running or not.
  • Setting the fan to “auto” will only run the fan when your HVAC unit is in its heating or cooling cycle.

So, which is best? Well, it depends on your personal preference!

Automatic saves energy but reduces air circulation.

The best benefit of using the automatic fan setting is saving energy. It won’t turn on when the AC and furnace aren’t doing their thing, so you won’t be paying for that energy to keep it running. It also means your fan motor will get to take breaks, reducing wear and tear and the need for repairs or a replacement.

On the flip side, allowing the fan to switch off will also stop the constant air circulation in your home. Some people might feel the air feels stagnant, as it won’t be filtered as often. That means dust, pollen and other allergens can linger longer.

Person adjusting home thermostat
Person adjusting home thermostat
Person adjusting home thermostat

Fan “on” constantly filters the air, but at a cost.

An always-on fan setting shines in areas where the automatic function falls short. If the fan is blowing constantly, the air in your home is continuously filtered and replaced. That means your indoor air quality should remain top-notch. This can be a lifesaver for people with asthma, allergies or other respiratory health issues.

Because your HVAC system is constantly pushing air through the filter, you’ve got to stay on top of changing it regularly. A clogged filter can reduce efficiency and reduce indoor air quality.

What are the cons of the “on” setting? Well, it is constantly running, which means you’re constantly using energy (and paying for it) to keep it running. It could increase electricity bills and wear out the fan motor. That means you might need to repair or replace it more often, but it might be worth the extra cost for people who need more air circulation.

Finally, using the fan when the air conditioner isn't cooling can draw humid air back into the house in the summer, making it feel warmer. That counteracts your AC’s cooling efforts!

It all comes down to personal preference.

Overall, it's up to you to weigh the pros and cons of each setting and choose one that best suits your needs. You can also investigate options like a variable-speed blower or hooking your HVAC system into a smart thermostat to improve efficiency. Smart thermostats usually give you more than two fan options and can help make your home comfortable without a huge increase in energy use.

If you need help with your HVAC settings, need repairs or are ready for an upgrade, connect with a reputable HVAC company in your area.


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