Variable Speed AC vs Two Stage AC vs Single Speed AC

Variable Speed AC vs Two Stage AC vs Single Speed AC – which one is the best for you? You shouldn’t choose a new heat pump or air conditioner without first understanding how differently they work. I’ve personally owned all three types of technology and can tell you from experience they are drastically different. Energy savings and efficiency is one thing, but the major difference is the comfort these three technologies deliver.

If you’ve been researching AC’s, you’ve probably seen a few terms describing the type of technology they use. I’m referring to variable speed compressors, multi-stage compressors, two-stage compressors, and the original, single stage compressor.

Most manufacturers are using the Copeland compressor brand in their ac units & heat pumps nowadays. However, there are big differences in how each of these compressor’s work, even the ones made by the same manufacturer. Understanding the differences will help you decide which one is right for your home or project.


Variable Speed AC vs Two Stage AC vs Single Speed AC – A Homeowner’s View

Everyone reading this has experienced single speed AC – it’s the one that started it all. The single speed air conditioner was invented by Willis Carrier in 1902 and is the technology we all grew up with.

A couple of decades ago two stage air conditioners and heat pumps became available to the residential market. Early adopters were amazed at the difference a ‘low speed’ and ‘high speed’ (which switched automatically as needed) made. Not only did their power bill decrease, but everyone in the home was also more comfortable.

Then came the game changer – the variable speed air conditioner. I’ll tell you the same thing our clients who own one say: You haven’t experienced true comfort from an AC unit until you’ve owned a variable speed inverter.

When I went from a single stage heat pump to a two-stage heat pump, I said I’d never look back. When I went from a two-stage heat pump to a variable speed heat pump I just said, WOW!

There’s a noticeable comfort difference when you compare single speed vs 2-stage air conditioners & heat pumps. However, there’s an exponential difference between a variable speed inverter and a two-stage unit. I will never own anything less – the difference in comfort, quiet, and reduced energy costs are that significant!



understanding variable speed air conditioners

Compressor Speeds Explained 

I created the infographic above to help explain Variable Speed AC vs Two Stage AC vs Single Speed AC. They see a picture is worth a thousand words. If a picture is worth a thousand words, feeling the difference yourself is worth a million words.

Below I break down the differences of Variable Speed AC vs Two Stage AC vs Single Speed AC one at a time.



Variable Speed (Inverter) Compressors

Most AZ air conditioning companies offer a variable speed AC, also known as an ‘inverter’ as they’re perfect for our climate. In recent years inverter heat pumps and air conditioners have taken the Phoenix area by storm. Companies like Trane, Lennox, and Carrier once led the pack in this technology.  Now, several other brands are building this technology and offering it a much lower price point. Bosch, Gree, and Amana are dominating the Arizona market because they offer a lot more bang for the buck. What was once only an option for our wealthiest clients, has become affordable for just about everyone. In fact, some of these brands sell variable speed inverters for about what the “big 3” sell two-stage and even single-stage units for.

What makes inverter technology special is its ability to only deliver the capacity needed for conditions at the time. An air conditioner’s capacity is commonly referred to in tons, i.e., 3-ton, 4-ton, 5-ton. More accurately, an air conditioners capacity is how many BTUH (British Thermal Units per Hour) it can deliver.

Inverters can ramp up or down in tiny increments depending on the “load” (how much cooling is needed). Variable speed inverter compressors can operate at many different speeds using as little power, or as much power as needed to get the job done.

It’s a Game Changer in Hot Climates Like Arizona!

Why is this technology the best for homes in Phoenix, Arizona, and other hot/dry climates?

Let’s consider this example:

A 2,000 sq. foot home may require a 5-ton unit to handle the load in mid-July when it’s 110° Fahrenheit outside. The unit should be properly sized to handle the most extreme heat – but we don’t always experience extreme heat. There are many days each year where we need to run our air conditioners, but don’t require all the capacity it’s capable of. For example, when it’s only 90°, all that capacity is just wasting energy. Believe it or not, all that extra capacity is not keeping you more comfortable either.

Again, in this example you still need to run your cooling system, but maybe the load is now only 3.2 tons. With a variable speed AC, you only use 3.2 tons, saving you money by not wasting energy.

By design variable speed heat pumps & air conditioners are also quieter – much quieter. If quiet is an important factor for you, an inverter is what you want.

High efficiency is the icing on the cake. Inverter units are amongst the most efficient on the market when operating at full capacity. Considering they’re usually running at a lower capacity, when 100% isn’t needed, they’re saving much more than single and two-stage models.



Multi-Stage / Multi-Step

Homeowners and contractors alike often confuse multi-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 manufacturer’s market these as “variable” when in fact they are “multi-stepped”. A few brands variable speed units have 6 – 10 “steps” up or down. The best inverter compressors typically have anywhere from 65 to 750 steps or stages.

Pro Tip: There’s no need to get caught up in the hype about how many stages the compressor has if it’s above 65. I own two variable speed systems with 65 stages. I couldn’t tell you when my units are running in 2nd, 10th, 29th, or 65th stage – nor do I care.

The only thing I care about is the fact that they keep my home comfortable 24/7 – as efficiently as possible. I have a 3rd variable speed inverter that has hundreds of speeds – I can’t tell any difference between the 65 speeds and the hundreds of speeds.

That said, it’s not accurate to call a 6 – 10 speed unit “variable-speed” in my opinion. Is it better than single-stage or two-stage, sure. However, true variable speed units have many dozens to hundreds of speeds.



Two Stage Compressors

Carrier, Lennox, Goodman, American Standard/Trane, Rheem, and others have two stage air conditioners in their lineup now, or once did. In the last few years many have begun sunsetting 2-stage models in place of newer variable speed models. At a recent Lennox meeting, their product managers said they were phasing out many 2-stage machines in favor of producing more inverter models.

Two-stage heat pumps and air conditioners as the name implies, have 2 speeds, high and low. High speed to handle the extreme temperatures and low speed for the milder weather. Again, I noticed a big difference in my own home when I switched from single to two-stage years ago. It performed better with more even temperature balance from room to room and it was quieter (in low speed). I did see a decent reduction in my utility bill as well.

It was certainly not the drastic difference I experienced when I installed variable speed, but it was a noticeable difference.



Single Stage Compressors

A single stage, aka one speed air conditioner is the one that started it all. If your air conditioning system is builder-grade or more than fifteen years old, it’s likely 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. As these units are often using more capacity than needed, they tend to turn on and off more frequently. The other types described above tend to run more constantly, but 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 machine, 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 even offer any of the newer technology because of that.

Our approach at Magic Touch Mechanical is quite different. I believe it’s our job educate our clients and propose multiple solutions. Compare the pros and cons of each, measure ROI, estimated annual savings, and cost to own. Then our clients can make an informed decision what they feel is best for them, their family, and finances.

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!



about the author rich morgan

Author: Rich Morgan, CEO, Magic Touch Mechanical & The Fire Place by Magic Touch


magic touch mechanical ac - there's magic in the air




Magic Touch Mechanical

942 West 1st Avenue
Mesa, AZ 85210
United States (US)
Phone: 4808558789

Fireplaces, Fire Pits, Heating, & Air Since 1997










HVAC 101