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How Much of a Difference Does the “Fan Only” Mode Make on an AC?

How Much of a Difference Does the “Fan Only” Mode Make on an AC?

June 26th, 2023

Spinning fan closeup.

When you make adjustments to the thermostat for your home’s HVAC system, you can also adjust how the blower fan works. The blower fan is responsible for pushing air through the air conditioner to receive cooling as well as to manage the circulation of air through the house. 

You probably know that the fan uses less energy to operate than the AC. But how much of a difference does it make? Is it useful to sometimes run the fan alone rather than turning on the AC? We’ll look at these questions more below.

The Fan and the AC in “Fan Auto” Mode

In this mode, when the thermostat detects that there’s a need for cooling in the house, it first activates the blower fan to begin moving air. Then the compressor will turn on, which is the main component that causes the AC to work and start cooling the air from the blower. When the thermostat detects the house has reached the cooling target, the compressor will then shut down, but the blower fan will continue to operate for a while longer to fully distribute the cooled air, and then it will shut down. 

“Fan Only Mode” and “Fan On”

You can run the fan independently of the AC by switching the fan to “Fan On,” which will keep the blower fan running whether there’s a demand for cooling or not. The AC can still come on, but you’ll have continuous air circulation when it’s not. 

You can also shut the AC off completely so only the fan runs. On some thermostats, is this “fan only” mode. On others, there’s no separate mode, you just set the fan to “On” and the AC to “Off.” 

“Circulate” Mode

Some newer thermostats have an extra option: “Fan Circulate.” In this setting, the fan turns on and off intermittently when there’s no need for the AC. This helps to create general air circulation without using much power. If you have this setting, we recommend using it as often as you can because it’s a good money-saver on hot days. 

The Power Difference

Now you know the different ways you can rely on the fan or the AC. Now here’s the power difference: the air conditioner’s compressor uses approximately 3,000 to 3,500 watts per hour to run. The blower fan uses around 500 watts per hour to run. That’s a huge difference! This is why running only the fan (regardless of which method you use) to help keep cool can save you significantly on your energy bills.

Of course, the fan on its own doesn’t have the cooling power of the air conditioner. The fan doesn’t actually cool the air: it creates air currents in the house that help people in it feel cooler, sometimes as much as 8°F cooler. That’s often the difference in whether you need to have the AC on.

We recommend that you try running the fan more often and see if you can raise the thermostat by several degrees. You may find you can stay comfortable while using the AC 5–20% less often—and you’ll see lower electricity bills. 

If you aren’t getting good cooling for your AC and the fans can’t overcome it, you may need air conditioning repair in Acworth, GA.

Dayco Systems has been Metro Atlanta’s choice for more than three generations. Contact us for all your home cooling needs.