Should I Set My HVAC System's Fan Setting to Auto or On?

AUTO vs. ON: have you ever looked at your thermostat and wondered which is the “right” setting? While most people will tell you that “auto” is the best setting, the answer depends on what is most important to you.

First, what’s the difference between your thermostat’s AUTO and ON settings?

Your thermostat’s AUTO setting will command your HVAC system to keep your home within a few degrees of the temperature you specified. Your thermostat’s ON setting will command your HVAC system’s fan to keep running non-stop, even when the system isn’t heating or cooling air.

Advantages and Disadvantages of the AUTO Setting On Your Thermostat

Most people prefer to use their thermostat’s AUTO setting for the following reasons:

• Typically, it saves energy and, therefore, money. AUTO is a good thermostat setting for people who want to save money by “setting it and forgetting it.” Your HVAC system will only use energy running the fan when the system is also cooling or heating air.
• The air filter lasts longer. Because the fan isn’t running constantly, there won’t be as much dust blowing into the air filter. This means you won’t need to replace your air filter as often as you would using the ON setting.

The AUTO setting does come with a couple of disadvantages:

• The fan can wear out faster. Starting up and stopping frequently can put wear-and-tear on the fan’s parts. Think of it like wearing out a brake pad in a car from frequent, hard braking on the road.
• Your home may have less even temperatures. Sometimes letting the fan run for a few extra minutes can help better distribute warm or cool air throughout your home. That doesn’t get to happen with the AUTO setting.

Advantages and Disadvantages of the ON Setting On Your Thermostat

If you prefer a more hands-on approach with your HVAC system, you might appreciate the following benefits of the ON setting:

• Your home can get heated or cooled more evenly. Running the fan continuously can help better distribute comfortable air in those areas that are harder to heat or cool.
• You’ll put less wear-and-tear on the fan. As mentioned above, your fan won’t be starting and stopping as much, which will put less strain on its parts.
• You may get better air quality. If your air filter is rated high enough and changed frequently, it will have the chance to capture more dust and other indoor air pollutants.

The ON setting has its share of disadvantages as well:

• You may rack up higher energy bills. Depending on how energy-efficient your HVAC system is, running the fan continuously could have a significant impact on your electricity bill.
• The circulated air will be less comfortable over time. After a while, the air coming from your vents will feel less cozy from your heater or less cool and crisp from your AC.
• You’ll need to change your air filter more often. With the fan running constantly, you can easily end up with a clogged air filter.

At the end of the day, there is most likely one setting that works best for your household and your home’s layout. If you’re not sure which is best, try experimenting for a month with the setting you typically don’t use and see if it’s more beneficial.

Expect more and get more at Tom's Mechanical, Inc.! For quality service and expert HVAC repairs and installations in Arlington, TX, contact us today at (972) 388-3669.