Air Conditioner High Cool vs Low Cool

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Updated May 14, 2023

Many people have an air conditioner with high cool vs low cool speeds, meaning that they feature two set speeds to cool your house controlled by the thermostat. This is also true for the leading through-the-wall air conditioners. The cooling speeds on these units cannot be changed or altered in any way, even on the best air conditioners, so you won’t end up with a cooler home any quicker if you set your thermostat lower.


  • When the day is particularly humid, run your AC on low cool to eliminate moisture from the air, reducing the perceived temperature.
  • A high cool fan allows you to chill the air more quickly when the weather is hot and dry.
  • Variable-speed fans may reduce electricity costs by using the energy more efficiently and adjusting the fan speed as needed.

However, you may be able to control whether your fan runs at a high or low speed using a switch on your thermostat. You may also want to consider whether aluminum vs copper coils in an air conditioner better suit your needs. Also, consider the brand of unit, like Armstrong vs Trane air conditioners.

Differences Between High and Low Fan Speed

High and low fan speeds, which can sometimes cause your air conditioner to squeal, also referred to as high and low cool on AC units, are designed to operate for different reasons. When you run your air conditioning on high or low cool, your unit has varying effects on the moisture levels in the air, the cost of operation, and the sound produced.

Insider Tip

Run your AC on its low-speed setting when it’s humid to reduce the moisture in the air.

Before selecting high-speed or low-speed fans, consider the outdoor temperatures, the indoor temperature, and the desired cold temperature for your comfort level. If you wish to attain a slightly cooler environment or already have an AC unit, consider getting a new air conditioner vs a ceiling fan.


Low fan speeds more efficiently cool your house on days with high humidity levels. As the air passes through the AC unit, the AC removes some moisture. The slower air movement extends the time for this process to occur.

High-speed fans still cool at the same rate on humid days, but excess humidity can make the air feel hotter than it is. This effect can be seen in the weather in more humid areas of the country. However, many people do not realize that the fan speed on an air conditioner affects the removal of water in the air because of the effect of heat on air conditioning coils.


In many cases, a two-speed fan costs less than a one-speed model. These settings and modes allow the air conditioning unit to adjust the fan speed as needed for the amount of cooling that needs to occur. A variable-speed fan will run at half-speed most of the time, reducing your power consumption. If you want up to four different fan speeds, check out our Luma Comfort EC220W review.

So, if you only need slight cooling, you probably only need to run it on low cool. In this setting, the AC unit will require less energy to complete the cooling process, which will save money on energy costs.

Similarly, the fan will use high cool when more cooling is needed, reducing the air conditioner’s overall running time.


Air conditioning systems set to run on high cool produce more noise than those on low cool because more air moves through the fan. Additionally, this air transitions through the AC at a higher rate, further adding noise.

A low-speed fan may sound quieter because less air moves at a slower speed. These factors combined can eliminate some of the whooshings sounds you may hear when your air conditioner turns on. Low cool allows you to run your air conditioner quietly and still be at a comfortable temperature.


Running your air conditioner on high all the time can cause it to cycle more frequently, so use your low-speed fan to avoid higher energy costs.


How is efficiency in AC systems measured?

An AC system’s efficiency is measured in terms of its energy efficiency ratio, which is the ratio of BTUs/watts input. You can also find its seasonal energy efficiency ratio (SEER), which measures its efficiency over a longer period.

Are high-efficiency air conditioning units expensive?

A high-efficiency AC unit is more costly than a standard version, but they cost less to run each time you use it.

What is an evaporative cooler?

An evaporative cooler uses the power of evaporation to cool air temperatures instead of the typical vapor-compression or absorption of an AC unit.

STAT: Variable speed blowers save energy by allowing the system to adjust its fan speed, and therefore its energy use, based on your home’s temperature demands. (source)

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