What is a Variable Speed Blower and Why Do I Need One?

If it’s time to replace your HVAC system in your Wake Forest, North Carolina, home, you may need to understand the difference between a single-speed blower, two-speed system, or variable-speed blower. By understanding the differences, you can choose an HVAC system that meets your comfort needs while saving you money on your monthly energy bills.

Single Speed

The term "single-speed" refers to the blower speed. Most traditional air conditioning systems have a single-stage blower. This means that your AC has one setting — high. So whenever it is running, it’s working at full capacity, irrespective of the temperature outside. Because it runs at full blast, energy-wise, it’s not as efficient as it could be.


A two-stage HVAC system has two levels of output, low and high. With this system, an air conditioner usually runs on the low setting and only kicks into high gear during very hot weather, or when it needs an extra boost to bring your home to the desired temperature. Since it generally runs on the lower setting, it is more energy efficient compared to a single-stage system.

Variable Speed Blower

A variable-speed blower operates at different speeds to accurately control the temperature in your home. "Variable-speed blower" is a term that refers to an air conditioner motor that adjusts to run at a different speed. This advanced technology constantly monitors and adjusts the blower settings to take into consideration anything in your HVAC system that could restrict airflow, such as the unit location, your ductwork, or even dirty filters.

Pros and Cons

Consider the pros and cons of each type of air conditioner system before deciding which system you will buy.

Single-speed system


  • It has a lower upfront purchase price.
  • It can usually be installed in any setting with any standard ductwork.


  • The system doesn’t last as long as a variable speed blower.
  • High energy bills because it runs on a single-speed — high.
  • Because they often cool your home with short, strong blasts, the temperature in your home is not consistently comfortable.

Two-speed system


  • A two-stage air conditioning system relies on the low setting 80% of the time to keep your home cool, making it more energy efficient compared to a single-speed system.
  • Since there is a slow, steady cool air flow through your home, your home’s temperature will remain more consistent.
  • It is a quieter system than a single-speed air conditioning system.


  • A two-speed air conditioning system will cost more than a single-speed system. However, this extra cost is regained because the two speeds are more energy-efficient.

Variable-speed system


  • A variable-speed system is the most comfortable option. On hot days your system will ramp up to top speed to cool your home quickly. But once your home is cool, it will automatically turn down to keep your home at a comfortable temperature.
  • A variable-speed system is the most energy-efficient system available.
  • Since your air conditioner doesn’t have to turn on as often, the noise level is lower than other systems.
  • Your air conditioner will run in long cycles, so a variable-speed air conditioner is better able to control indoor humidity during the summer months, creating a more comfortable environment.
  • Better air quality. Since a variable speed air conditioner system runs in longer cycles, more air passes through the HVAC system’s air filter, resulting in cleaner indoor air.


  • Typically a variable-speed system has higher upfront costs, but a variable speed system also produces the highest monthly energy savings compared to a single- or two-speed system.

If you are considering variable-speed technology in your home, you are choosing a more energy-efficient system that controls temperature and humidity far better than a one- or two-stage system. Coupled with lower monthly energy costs and improved indoor air quality, it’s clear that making the change to a variable-speed system can make a difference in your life.

Saving money and reducing your energy consumption is easy when you opt for a variable speed system. Alford Mechanical Heating and Air Conditioning can help you choose and install the best system for your home. Our friendly professionals can answer all your HVAC questions, call us at 919-246-5265.

Image provided by Shutterstock

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