What is the best fan setting for a furnace?

Author: Erwin Schimmel IV  |  Last update: Sunday, October 5, 2025

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously.

What setting should my furnace fan be on?

Energy Efficient Heating Advice for How to Set Your Furnace Fan in Winter. When it comes to whether you should set your furnace fan to “on” or to “auto” in winter, the answer for me is “auto” because it's the move that has the most to do with energy efficiency.

Should my furnace fan be on auto or circulate?

Setting your thermostat to auto will allow your system to be more energy-efficient since the fan only runs when the system cycles on, not continuously. Typically, the fan will turn on 30 to 60 seconds after a heating or cooling cycle starts and then turn off a minute after the cycle ends.

Is it better to leave furnace fan on or auto?

Using the “Auto” Setting

Increased energy efficiency by running the fan only when needed. Extended filter life as the fan operates less frequently. Lower energy bills due to reduced electricity usage.

What should a furnace fan be set at in winter?

There is no one right answer. The correct furnace fan setting will depend on the type of heating system you have and your indoor comfort preference. When the furnace fan setting is ON, it means the fan is always circulating air throughout the home—even if there's no heat coming from the furnace.

Fan On & Auto which one should I use?

Is it OK to run furnace fan constantly?

Running it continuously may lead to more frequent maintenance and repair needs. However, the added comfort and air quality benefits often outweigh these concerns. Noise: If you're sensitive to background noise, you might find the constant hum of the furnace fan bothersome.

What setting should my fan be on for cold weather?

During the colder months (winter), your ceiling fan should spin clockwise. During the warmer months (summer), your ceiling fan should spin counterclockwise. Most ceiling fans have a small switch on the fan body to control the spinning direction. Fans at low speeds will pull cold air upward more efficiently.

Is it OK to just run the fan on the furnace?

In some cases, like if you have an old model or if high temperatures make conditions dangerous, running your fan continuously is not a good idea. But in most other cases, continuous use of the furnace fan actually has a lot of benefits that will sway many homeowners to the affirmative.

Should I put my thermostat on auto or fan?

"AUTO" is the more energy-efficient option, as it runs the fan only when heating or cooling is actively needed. "ON" keeps the fan running continuously, which can help with air circulation and filtration but may consume more energy.

Is it expensive to run furnace fan all the time?

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 bill.

What is the best fan setting for a heat pump in winter?

During the winter months it is best to allow your heat pump to run at a lower fan setting and spread heat out more evenly over a longer period of time. The reason for this is two fold: Maintaining temperature over a longer period of time is more efficient than getting a room to temperature quickly.

Why is my heat blowing out cold air?

The heater might blow cold air rather than warm if the gas line supply has been turned off. This usually happens when something goes wrong with the heater, and it breaks. For example, maybe there was a problem with a gas valve, the gas supply pipe, or something else in your furnace broke down.

Should you run a furnace fan in summer?

Turning the fan on in the evening after a hot day and opening the window to let in cool air will cool the home off quickly. Circulating air with the blower fan on your furnace also evens out the air temperature throughout your home cooling rooms on upper levels.

Should my fan be on auto or circulate?

Which Thermostat Setting Is Best: On, Auto, or Circulate? Given the amount of money it costs in increased utility bills and filter purchases to keep your AC fan running constantly, most of the time, you'll want to keep the fan in the “auto” position.

What is the best setting for a furnace?

Most recommend keeping your furnace between 68 and 70 degrees. You will find that after about a week at a lower temperature, your body becomes accustomed to it, and it no longer feels cold to you. You will also be surprised what some cozy sweaters, socks, and throws will do to keep you warm and comfortable.

What should my furnace fan speed be?

What Is the Best Speed for My Blower Motor? In the interests of efficiency, your blower motor should be moving at least 400 cubic feet of air per minute for every ton of your furnace.

Should your furnace be set on auto or fan?

The main benefit of setting the thermostat to 'Auto' is that it will result in more energy efficient usage. This is because the fan will run only when it's required. Also, the air filter will need to be changed or cleaned less frequently when the thermostat setting is set to 'Auto'.

Why is my furnace not blowing hot air?

If your furnace is not blowing hot air, or is not operating at all, a component called the fan limit switch or high limit switch may have malfunctioned. You may also see an error message on your thermostat, or a blinking LED light on the furnace control board.

What mode should my thermostat be on?

You'll want to have your thermostat set to heat mode in the wintertime and air conditioner auto mode in the summertime. In order for your system to run on auto mode, you'll need to have either the heat mode or cool mode on. This way, your thermostat knows whether to turn on the furnace or the air conditioner modes.

Is it good to keep the furnace fan on all the time?

Pros of Continuous Fan

The primary benefit of running your HVAC fan consistently: Air circulation improvements. Running the fan more often means air in your home circulates faster, leading to everything from more even temperature distribution to faster heating or cooling.

What is the circulate fan setting on a thermostat?

When Circulate mode is chosen, the fan turns on to circulate the interior air 35% of the time that there is no call for heat or AC. Of course, if there's a call for heat or cooling, the fan again runs automatically, even if Circulate is chosen.

Does running furnace fan bring in outside air?

In most cases, your HVAC system does not pull air from outside when it is heating or cooling your home. Instead, it recirculates the air inside your home.

What setting should my fan be on?

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. There is better dehumidification in your home during the summer months. When your fan is set to AUTO, moisture from cold cooling coils can drip and be drained outside.

Does fan mode make it colder?

Fan mode in an AC unit is a setting that turns off the unit's cooling function, leaving only the blower fan running. This mode doesn't cool the air; instead, it circulates air within the room. It can help distribute existing cold air throughout the room, especially when the AC compressor is not operating.

At what temperature should you not use a fan?

(Fans in windows can blow cooler air into a room from outside.) Fans do not cool the air, so air currents flowing over the body must be cooler than your body temperature to cool you down. When indoor air temperatures are hotter than about 95 °F: Fan use may cause your body to gain heat instead of lose it.

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