Increased Energy Consumption: While running your furnace fan continuously has benefits, it comes with a cost. Continuous fan operation consumes electricity, which can lead to higher energy bills. However, this increase is generally offset by the improved efficiency and comfort it provides.
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.
Running the fan all the time will usually help keep temps in the home more even and the air is always being filtered. It will cost a little more in electricity and more frequent filter changes, but that's the price of better comfort and air quality.
In the summer it is okay to run the fan on continuously because it allows the house to stay cool as it circulates the cool air. This is not a good idea in the winter though as it cools the house down faster and does just that keeps turning the system on/off continuosly fighting the thermostat to satisfy.
Running the fan constantly uses a bit more energy, as you might expect, and this can increase your utility bill.
Increased Energy Consumption: While running your furnace fan continuously has benefits, it comes with a cost. Continuous fan operation consumes electricity, which can lead to higher energy bills. However, this increase is generally offset by the improved efficiency and comfort it provides.
Leaving the fan running reduces wear and tear on the motor since it's not starting and stopping repeatedly. It's also beneficial to boost filtration, but leaving it on this setting has more drawbacks than benefits. When it runs nonstop, the fan consumes more energy, and the air filter needs frequent replacement.
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.
Although it could run for over a 24 hour period, it is still best to turn off your ceiling fan when you are at work or out of the house for an extended time to give the ceiling fans' motor a rest and reduce electricity use and cost.
The switch that allows you to do this is commonly known as a summer switch. A summer switch is a small toggle switch attached to the furnace, which, when set to the 'on' position, will allow the furnace fan to run continuously. Another common place to find a summer switch setting is on your thermostat.
The fan will normally kick in 1½ to 3 minutes after the thermostat signals the heater to start. It should then keep the blower running during the heating cycle. When the cycle ends, the blower fan should turn off a few minutes later.
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.
Year-Round: If you have a newer HVAC system, leaving the furnace fan on all the time can enhance air quality, regulate humidity, and improve overall energy efficiency.
Running the Fan Continuously
This offers benefits for your home such as: Improved air circulation throughout your living spaces. Enhanced indoor air quality by filtering air continuously. Reduced motor stress by minimizing frequent starts and stops.
Running a fan throughout the day is inexpensive—much lower than the cost of running an AC unit alone—and using both in conjunction with each other means that you won't have to keep your air conditioning running all day.
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.
–Running fans for long periods could cause them to overheat.
Fans start to get hot when the air is pushed out of the blades, but this only lasts a short time. It will cool down quickly. – Fans don't need to be left on at all times, so if you have a fan in your room that you don't plan on using all day, leave it off.
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.
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.
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.
Increased Furnace Lifespan
If your system was properly installed and the ductwork is correctly sized and configured, running the fan continuously won't do any harm. It can reduce the strain on your furnace, potentially extending its operating life.
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.
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.
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.