Setting Your Thermostat Fan in the On Position vs. Auto

Most thermostats have two fan settings: on or auto. Is there really a benefit to choose one over the other? If you want to keep your air conditioner running as efficiently as possible, there is definitely a benefit to choosing either on or auto. If you keep your thermostat’s fan in the “on” position, your system’s fan will be constantly running.

While this will continually push fresh air into your rooms (which can help keep them comfortable), you might not need your system to do this.

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On the other hand, the “auto” setting, will turn the fan on only when your system is actually heating or cooling a room. It automatically switches on when your air conditioner is producing cold air and then switches off again when the system has cooled your rooms to the desired temperature.

But why would you choose one of these setting over the other? Here are a few reasons you might choose each setting:


Choosing on means that your fan will continue to run, even if your system is not heating or cooling your rooms. There are a few reasons why you might choose this setting.

For example, if you do not want to be constantly running your air conditioner during the summer but you still want some air movement to keep your rooms cool, you might choose this setting. Often, home owners will try to save power by turning off their air conditioner (or setting it relatively high so that it is unlikely to turn on), but keep their thermostat fan in the on position, so that they still get some fresh air into their rooms.

You might also choose this option occasionally in the winter. If you overheat a room, for example, you might want your fan to continue to blow, to help air out the room again.

The fan can also help to process cooking or chemical smells in your home, making it a useful tool for when opening a window or door is not a good option for airing out your home.


In general, auto is the best setting for your thermostat fan. It has a huge number of benefits, including using less power and being more energy efficient than the on setting. Here are just a few of the reasons that auto is a much better setting than any other you might be presented with:

1. Lower energy costs

When your fan is set in the on position, it will continue to run all day and all night until you switch it off again. This means that, during this time, you have to be providing power to it.

While it might not seem like a big deal to be powering the fan during this time, you will quickly see the bills start to stack up. When you use the auto setting, on the other hand, you will likely find that your fan is only on for a few hours each day.

This can drastically reduce the amount of money you have to pay to run your Sarasota air conditioner. It is just a much better option for those who are trying to save money on their heating and cooling costs.

2. Fewer repairs

The more frequently you run your system, the more stress it will incur and the more repairs it will need. As with any other piece of machinery, if you just run your fan all day, every day, it will need to be repaired far more often. While your entire system might not need more frequent repairs, you will see the components that run your fan need more attention, more often, which can be incredible expensive.

The auto setting, however, means that your fan only turns on when it is actually needed to push cold or warm air into your rooms, which means far less stress and far less wear and tear on your fan and, in the long run, fewer repairs that you have to pay for.

3. Better dehumidifying.

When your fan is set to on, your system will not be as good at dehumidifying itself as it would be if your fan was set to auto.

Why does this happen? Because while your air conditioner is running, the coil gets cold. This encourages it to collect water (as water that hits it will condense and collect on the coil). When your fan is set to auto, the water is given time to evaporate.

When your fan is set to on, however, it will carry all of that moisturized water into your home, causing your indoor humidity to spike. This can contribute to mold growth, as well as promote a wide variety of other pests to invade your home and spread.

Next week, we’ll dive deeper into what a dehumidifier is, so make sure to check back soon!

4. Protects your home from duct leakage.

The more often you run your fan, the more of your air is going to be lost through your supply and return air ducts.

If your fan is constantly running, your air is moving more, and therefore you are losing more of your cooled or heated air. If your fan is set to auto, however, your air is moving much less and you are going to lose far less of the air that you have paid to keep at a comfortable temperature.

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