When the weather begins to cool off, you might be thinking about how you’ll take full advantage of your heating and cooling. After all, HVAC bills frequently contribute a significant piece of your monthly electric bill. To try and find ways to lower their HVAC bill, some owners take a closer look at their thermostat. Is there a setting they could use to boost efficiency?

The bulk of thermostats come with a ‘Fan’ or ‘Fan On’ setting. But if the fan is running during a normal cycle, what can the fan setting provide for your HVAC system? This guide will help. We’ll walk through just what the fan setting is and when you can use it to reduce costs over the summer or winter.

What Is the Fan Setting on My Thermostat?

For the majority of thermostats, the fan setting indicates that the system's blower fan remains on. A few furnaces will generate heat at a low level in this setting, but for the most part heating or cooling isn’t being generated. The ‘Auto’ setting, conversely, will start the fan over a heating or cooling cycle and shut it off after the cycle is complete.

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 using the Fan/On setting:

  • You can keep the temperature in each room more consistent by permitting the fan to keep running.
  • Indoor air quality will be highest since continuous airflow will keep passing airborne particles through the air filter.
  • A smaller amount of start-stop cycles for the blower fan helps expand its life span. As the air handler is often a component of the furnace, this means you could avoid needing furnace repair.

Disadvantages to using the Fan/On setting:

  • A nonstop fan will likely raise your energy bills somewhat.
  • Continuous airflow may clog your air filter in a shorter amount of time, increasing the frequency you’ll need to replace it.

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

In the summer, warm air can linger in unfinished spaces like the attic or an attached garage. If you use the fan setting, your HVAC system may pull this warm air into the rest of your home, pushing the HVAC system to work harder to maintain the set temperature. In extreme heat, this may lead to needing AC repair more quickly as wear and tear increases.

The reverse can happen in the winter. Cooler spaces like a basement will hold onto cooler air, which can eventually flow into the rest of your home. Leaving the fan setting on will sometimes draw more cold air upward, increasing the amount of heating you need to stay warm.

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

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

Your home deals with hot and cold spots. All kinds of homes deal with persistent hot and cold spots that quickly evolve to a temperature different from the rest of the house. The fan setting might help minimize these changes by consistently refreshing each room’s supply of air.