As the weather begins to cool off, you might be concerned about how you’ll take full advantage of your heating and cooling. After all, HVAC bills routinely contribute a large piece of your monthly electric bill. To try and find ways to save, some people take a closer look at their thermostat. Could there be a setting they could use to boost efficiency?

Most thermostats have a ‘Fan’ or ‘Fan On’ setting. But if the fan is on during a typical cycle, what does the fan setting provide for the HVAC system? This guide can help. We’ll walk through just what the fan setting is and whether you can use it to reduce costs in the summer or winter.

What Is the Fan Setting on My Thermostat?

For the bulk of thermostats, the fan setting signifies that the air handler’s blower fan stays on. Some furnaces will operate at a low level with this setting, but in general heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will run the fan through a heating or cooling cycle and switch it off once the cycle is finished.

There are advantages and disadvantages to using the fan setting on your thermostat, and what's ideal {will|can|should]] depend on your personal comfort needs.

Advantages to switching to the Fan/On setting:

  • You can keep the temperature throughout your home more uniform by enabling the fan to keep generating airflow.
  • Indoor air quality can increase as steady airflow will keep passing airborne particles through the air filter.
  • A smaller number of start-stop cycles for the blower fan helps lengthen its life span. Since the air handler is often a component of the furnace, this means you can minimize the risk of needing furnace repair.

Downsides to using the Fan/On setting:

  • A nonstop fan could add to your energy expenses by a small margin.
  • Nonstop airflow can clog your air filter up more quickly, increasing the frequency you will want to replace it.

Should My Thermostat Be on Fan or Auto in Summer/Winter

Through the summer, warm air will sometimes linger in unfinished spaces such as the attic or an attached garage. If you leave the fan on, your HVAC system may gradually move this warm air into the rest of your home, compelling the HVAC system to work harder to preserve the set temperature. In extreme heat, this can lead to needing AC repair more regularly as wear and tear gets worse.

The reverse can occur during the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually make its way into the rest of your home. Leaving the fan running could draw more cold air upward, increasing the amount of heating you need to keep warm.

If you’re still trying to determine if you should switch to the fan/on setting, remember that every home and family’s comfort needs will vary. Leaving the HVAC system’s fan on might be best for you if:

Someone in your household deals with allergies. Allergies and similar respiratory conditions can be tough on the family. Leaving the fan on is more likely to increase indoor air quality, helping your family breathe easier.

Your home experiences hot and cold spots. All kinds of homes wrestle with stubborn hot and cold spots that quickly shift to a temperature different from the rest of the house. The fan setting should help minimize these changes by steadily refreshing each room’s supply of air.