Since the AUTO setting means the fan is only engaged when the system is on, rather than constantly blowing, AUTO is the most energy-efficient option between the two settings. This means you'll be using less energy and saving money on your electric bill by using the AUTO setting.
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.
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. It is not, however, the only thing you can do this winter to bolster your HVAC system's energy efficiency.
Pros of Running Your Furnace Fan Continuously
This helps eliminate cold spots in your home and provides a more comfortable living environment. Enhanced Air Filtration: Continuous fan operation means your furnace's air filter works 24/7.
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.
Leaving your AC fan set to ON allows the moisture in your home to accumulate and reach mold-growing levels of humidity. To ensure that you and your family stay cool and healthy this summer, keep your AC thermostat fan setting to AUTO.
Keeping the fan on creates a more even distribution of heating and cooling, circulating the air if you have cold or hot spots in your house, like a bedroom above a garage. Less frequent starts and stops of the fan can reduce the stress from startup, and potentially help extend it's lifespan.
The average kWh in the US costs about $0.12 so it costs about $43 per month, or about $520 per year, to run a fan continuously. At this point, it should be pretty obvious that AUTO costs less than ON but let's math it out to its logical conclusion.
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.
During the coldest days in winter, it is normal for a furnace to run almost constantly to keep the home warm. As long as the furnace is running efficiently and not making strange noises, the constant operation is likely nothing to worry about. But in general, your furnace should not constantly be running.
The difference between fan settings:
If you turn the fan to “on”, the blower will continue to run after the system is turned off, but if you set it to “auto”, it will allow the blower to run off and on intermittently in time with the heating or cooling system.
Running your furnace fan continuously in winter has its pros and cons. It can improve air circulation and quality but may also lead to higher energy bills and increased wear on your system.
With a furnace blowing cold air, the first question you should ask is if the furnace has been turned ON. Two thermostat issues that could cause your furnace to blow cold air include (1) your thermostat is still set to COOL, not HEAT and (2) your thermostat fan is set to ON, not AUTO.
Using the “Auto” Setting
This setting offers benefits including: 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.
"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.
If your furnace fan won't turn off, you most likely have one of these 3 problems: Your furnace fan limit switch is set to “manual override” The fan limit switch is faulty and needs to be replaced. There's a problem in your thermostat wiring.
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.
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.
Your blower motor circulates air through the furnace and can provide uniform temperatures. Many people leave their HVAC fan on all day, while others opt for two to three cycles per hour, ranging from ten to 25 minutes, depending on how close to heating or cooling temperatures they are.
Since the AUTO setting means the fan is only engaged when the system is on, rather than constantly blowing, AUTO is the most energy-efficient option between the two settings. This means you'll be using less energy and saving money on your electric bill by using the AUTO setting.
Although it is perfectly safe to run HVAC continuously, there are a few times you should shut it down. First, if your home is experiencing high summer temperatures and you have ductwork in the attic. It is difficult for even the best-insulated systems to fight off extreme temperatures.
One of the easiest ways to reduce dust in your home is simply to turn on your HVAC fan after dusting or vacuuming by switching your thermostat from “auto” to “on.” This allows your HVAC system's filter to remove any airborne dust from your home before it can settle or continue to circulate through your home.
A fan's housing will get warm after prolonged use due to the fan's motor generating heat when converting electricity into movement. This heat is why many people think it is unsafe to leave fans running; however, it is normal and will dissipate from the fan's housing and not exceed a safe limit.
Contrary to popular belief, keeping your HVAC fan on may extend its service life, provided the equipment was properly installed and your ductwork is correctly sized. Set to off, a newer, energy-efficient HVAC system goes through more wear and requires more maintenance than if the fan is set to the “on” position.
Turning your thermostat to the wrong setting by focusing solely on temperature rather than humidity is a common mistake. For example, running your AC unit in fan mode might increase the airflow in your home, but it will also increase the humidity level.