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Single Stage, Two Stage, Variable Speed Air Conditioners

What is the difference between single stage, two stage, and variable speed air conditioners? Learn about the cost to benefit of each system and how efficiency can help save on utility costs while increasing comfort throughout your home.

Revised:

November 8th, 2022

So, you're looking to replace your cooling system and while looking at products, you come across something that says there are different types of systems: single-stage, two-stage, or variable speed. What’s that mean and what's the difference between each type?

In this video, we'll compare each type and show you the benefits that each system has to offer.

Hi, I'm Brad from Fire & Ice!  Weather y ou’re replacing just an air conditioner or a full system, you need to make sure your unit is best suited for your specific home.  In this video, we'll cover the difference is between a single-stage, two-stage, and variable speed cooling system and what are the benefits of each system is, as well as share some example products. By the end of this video you'll know what type of system is right for you.

Single-stage Air Conditioners

A single stage air conditioner is an air conditioner that operates at 100% capacity all the time or off entirely. When we size air conditioners in the central Ohio region, we size them for when it's approximately 88 degrees outside which is when they need to be at 100% capacity.

Single stage ACs are going to be entry-level equipment and they’re often best for budget-conscious homeowners. They’ll do the job, but won’t offer you the highest levels of cooling efficiency and comfort.  If you have rooms with inconsistent temperatures, a single-stage may not be the best choice. 

Some of the examples of a single stage air conditioner are the Infinity 16 and Performance 13 by Carrier. The right fit for a single stage air conditioner would be a customer that doesn’t experience a lot of temperature swings or hot & cold spots in the home.

Two-stage Air Conditioners

A Two-stage air conditioner is one that operates at two different capacities which increases efficiency and saves energy and utility costs. The first stage usually operates at about 60-65% of total capacity and then the second stage operates at 100% capacity when needed.

Think of it like gas mileage. It’s more efficient to drive at slower speeds than higher speeds and slamming the pedal can produce long-term wear and tear on your car. The benefits of having a second, slower stage is somewhat similar in terms of efficiency and system usage.

A two-stage air conditioner is going to be able to remove moisture much better because it does have a little longer run time. Those run times are using less energy too, so it’s more cost-effective and capable of removing more heat from your home at a lower cost than a single-stage unit.  

An example of a product that has two stages of cooling would the Performance 17 model by Carrier. The right fit for a two-stage air conditioner would be a homeowner who is having issues controlling temperatures throughout the house. If they have a two-story home, a multi-stage will be a much better fit for them.

Variable-Speed Air Conditioners

Variable speed cooling is exactly what it sounds like, and involves cooling equipment that can have hundreds of different cooling stages. Depending on the equipment, the lowest stage starts at about 35% of the unit’s total power, and each additional stage can be as little as a fraction of a percent more. Its final stage goes up to 100% capacity and power of the system.  Everything is based on the outdoor temperature, the indoor temperature, and the run time that is needed to properly cool your home.

The biggest benefit of a variable speed air conditioner is that you have better temperature control in the house- to within a half a degree or less.  You're going to have better humidity control in your home with this type of air conditioner as well.

Additionally, these units are the most cost effective over time. It might seem strange, but a unit that runs continuously at the lowest stage will use less energy than a single-stage unit that has more downtime but is always at 100% capacity when it’s on.

An example of a product that has variable speed technology that would be the Infinity 19VS air conditioner by Carrier. The right fit for a variable speed system would be homes that are a little larger, have higher humidity levels, or have uneven temperature swings.

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