Variable Speed Air Conditioner vs Two-Stage vs Single Speed

Variable Speed Air Conditioner vs Two-Stage vs Single Speed is the third article in the series on the subject of: What are the differences between the major air conditioners and brands? Clearly there are a lot of people researching the difference in central air conditioners before replacing or installing new HVAC systems in their home, so we’ll keep posting if you keep reading!

In our first article “Trane Vs. American Standard, What’s The Difference” (our most read post of all time), we pointed out that there really is no difference in the product itself – read the entire article, but there were other considerations for homeowners looking to install new a new air conditioner other than just doing a Trane vs. American Standard comparison.

Our second of the series, “Trane vs Lennox vs Goodman vs Carrier”, (read the entire article) explored the actual components of each system a little deeper, and let some of the manufacturers secrets out of the bag!

For this installment of the series, let’s look at some of the technology available today that many homeowners are trying to understand and compare. Specifically, we are going to focus on one major component; the air conditioner compressor.

If you’ve been researching AC’s you’ve probably heard about variable speed compressors, multiple stage compressors, two-stage compressors and the original, single stage compressor. Although most manufacturers are using the Copeland compressor brand in their ac unit nowadays, there are big differences in the technology of each.



understanding variable speed air conditioners

Click for Infographic: Understanding Variable Speed Air Conditioning


Compressor Speeds Explained 


Variable Speed (Inverter) Compressors

If you live near Phoenix, AZ where temperatures can reach 110 degrees or more, and you call a nearby air conditioning company for a new ac unit install quote, chances are most companies will offer a variable speed compressor also known as an inverter driven or inverter compressor. One great example of a company leading the industry in this technology is Lennox. The Lennox XC25 and Lennox XP25 are advertised as “65 air conditioners in one”.

What they mean by that is the air conditioning capacity also known as tons, can ramp up or down in tiny increments depending on the “load” or how much cooling is needed to get the job done. The reason they say 65 in 1 is because it can ramp down to 35% of its total capacity (100% – 35% = 65%).

The reason that technology is recommended in Phoenix, Arizona is; you may need a 5-ton unit to handle the load in mid-July when it’s 110F outside, but what about in September when it’s only 90 degrees? You still need to run your cooling system but maybe the load is now only 3.2 tons. With an inverter driven variable speed compressor you only use what you need, thereby saving you money by not consuming energy you don’t need.

Compare that to a place in the high country like Flagstaff, AZ and more than likely the upfront costs of a variable speed unit will not have as good a return on investment since the temperature swing throughout the cooling season isn’t as great.

By way of comparison the 2017 Trane variable speed compressor has significantly more “speeds” or “steps” than the Lennox variable speed compressor. Whereas the Lennox compressor in the XC25 and XP25 can adjust itself in increments of 1% – the Trane XV20i can adjust in .10% increments. In fairness to both: This is a close matchup so if you are considering installing a variable speed air conditioner on your home, you need to read the Trane vs. Lennox articles in our other posts.

Multi-Stage / Multi-Step

Homeowners and contractors alike often confuse multiple stage compressors with variable speed compressors. Although still great technology, these are not equal to a true variable speed compressor. The reason for the confusion is a few of the manufacturers market these as “variable” when in fact they are “multi-stepped”, many having about ten “steps” up or down -think about a ten speed bike. We’re not mentioning any names here, just do your research!

Two Stage Compressors

Carrier, Lennox, Goodman, American Standard/Trane, Rheem and a few others all have two stage air conditioners in their lineup now as they are pretty commonplace today. Think about two stage as high speed and low speed. High speed to handle the extreme temperatures and low speed for the milder weather.

There are some differences in how the manufacturers accomplish two stage however. For example, Goodman (a Daikin brand – the largest air conditioning company in the world) uses one, 2-speed compressor. Whereas, Trane / American Standard (an Ingersoll Rand company) uses two individual compressors (large and small) inside the same condensing unit in many of their models.*

*UPDATE – Since the original publication of this article it is important to note that Trane and American Standard have stopped manufacturing the dual-compressor models and have switched to a single-compressor with two stages. The paragraph below only pertains to existing dual compressor units that were installed prior to last year. 

There is a disadvantage to the 2-compressor design that we’ve discovered over the years. Before we address that disadvantage we must emphasize: We have installed hundreds, perhaps thousands of Trane and American Standard units all over the Phoenix Metropolitan area…they make a great product and we still recommend and install them today (as well as Lennox, Goodman, Mitsubishi and a few others). The disadvantage comes up when there is a compressor failure, and it really hits hard when the unit is out of warranty. When one breaks Trane / American Standard requires both be replaced. This tends to be a very expensive repair and should weigh into your decision when comparing products and brands.

Single Stage Compressors

A single stage aka one speed compressor is the one that started it all. Chances are, if your air conditioning system came with your home or is more than ten years old, this is what you have now.

From an efficiency standpoint, these are the least efficient type as they are always running at 100% capacity. A compressor draws the most power when it kicks on, and since these units are often using more capacity than needed, they tend to turn on and off more frequently vs the other types which tend to run more constantly at lower capacities.

There is a school of thought which does have its merits that simpler is better. The thought process being less to go wrong means a more reliable compressor, and there is a case to be made that there is some truth to that. We sometimes hear air conditioning contractors saying the old technology is “tried and true”, and some flat out refuse to offer any of the newer technology because of that.

Our approach at Magic Touch Mechanical is a little different, we feel we should educate our clients and propose multiple solutions, look at the pros and cons of each, measure ROI, estimated annual savings, and cost to own, so our clients can make an informed decision what is best for them and their families. Before considering a new air conditioning installation, make sure to research which system type would best fit your home’s needs.

Make sure to visit our blog again for more in this series. If you live in the Phoenix area and are considering a new ac unit or any of the other products and services we offer, contact us for more information and tell us you read our blog!


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