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AIR QUALITYCOMMON HVAC PROBLEMSCoolingCOST SAVINGSHeat PumpsHeatingIN CHARLOTTEOctober 25, 2021Benefits Of Setting Your Fan On Your Thermostat To Auto vs On

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Benefits Of Setting Your Fan On Your Thermostat To Auto vs On

“Should I set my HVAC fan to on or auto?” is a question we typically get from South End Heating & Air customers – in addition to “does running the fan on my air conditioning system use a great deal of electrical power?” It’s a debated topic throughout the market, so we’re going to provide you the pros, the cons, and our recommendation.

Setting Your Thermostat Fan to “ON”
When you set your fan to “ON,” you’re making it keep running 24 hours a day, 7 days a week, despite the heating or cooling setting. There are a few positives to this feature.

Pros to Running Fan on Air Conditioning Unit Continuously

  • Less regular starts and stops of the fan can lower the stress from start-up, and potentially help extend it’s lifespan.
  • Keeping the fan on develops a more even distribution of heating and cooling, circulating the air if you have cold or hot spots in your house, like a bed room above a garage.
  • Leaving the fan on 24/7 makes the air cleaner, as the air is pulled through the filter or UV light system. This can be much better for people with allergies.

While keeping your fan on 24/7 may be more energy efficient, there are a few disadvantages to leaving your fan on all of the time.

Cons to Keeping Fan Continually Running

  • It could cost you hundreds of dollars a year. The average unit has a 500 watt fan, which uses almost as much energy over the course of the year as a refrigerator, resulting in a $50/month expense.
  • Throughout the summer months, the ducts in your attic and near to your walls can fill with warm air, resulting in the fan blowing hot air into your home. You might end up running your A/c even more, to counterbalance the extra heat. You might likewise bring in more damp and unclean air into the system, which then gets distributed throughout your home.
  • By keeping your fan on in the winter season, you may feel cold air coming out of your vents. The air temperature level will be comparable to the space temperature, your home will feel cold.
  • Your HVAC filter will clog up quicker (despite the fact that indicates it’s working), but you will have to change your filter more often.
Thermostat Set To Auto
Thermostat Set To Auto

Setting Your A/c Fan to “AUTO”
Your other option is to set your fan to auto, which means the fan runs when directed to by the unit. Here are the benefits and drawbacks to this technique.

Pros to Allowing Fan to as Needed

  • This option is far more cost effective, since you are utilizing less energy. The fan’s “AUTO” setting works with your heating + cooling system, so your fan is running the least amount of time required, at the slowest speed.
  • Your heater filter will last longer.
  • Better dehumidification. When your fan is on “AUTO,” wetness is able to leak from the cold cooling coils and drain outside. When the fan is running 24/7, that moisture doesn’t have a chance to leak outdoors. Instead, it blows back into your home, and, as a result, your air conditioner then needs to work ever more difficult to draw that extra moisture out of the air.

Cons to Permitting Fan to as Needed

  • You may feel a less even distribution of heating & cooling, since as soon as the thermostat setting is reached, the fan stops moving air to other spaces in the home.
  • More regular starts and stops will make reduce the fans longevity.

A/C Fan On Or Auto: Which HVAC Fan Setting Is Best?
When keeping your air conditioner fan on or car, there’s no consensus  recommendation that we make to homeowners, since everyone has different needs. If for example you have a family with allergies, it may make sense to leave the fan on constantly in order to filter more of the allergens in the air.

PRO SUGGESTION: Many more recent thermostats will have a variable speed blower or “circulate” alternative, that allows you to set the fan on for a specific quantity of time every hour. The blower will instantly perform at various speeds, giving you the advantages of lower electrical costs and increased comfort.


At South End Heating & Air we specialize in Furnace Repair and Replacement, contact us for a free consult. We’ll evaluate your system and help make recommendations for optimum value. After all, we want to keep you cool all summer long and warm in the winter. Just schedule a visit with one of our technicians to talk about how we can help with your thermostat’s settings. Would you like to learn more options our techs can help you with? give us a call 704-684-5339