Single Stage vs Two Stage Air Conditioner | One Should Be Avoided

Air Conditioning

Before you decide whether to purchase a new single stage or a two-stage air conditioner for your home, you have to know some key information about each product and how it can benefit you and your family. Most sources will give you almost the same answer which of the two is the best, but you might be surprised by what they don’t tell you. 

DP single vs two stage air conditioner

The most basic difference between the single stage vs two stage air conditioner is the type and speed of the compressor. The compressor is the heart of an air conditioner and is used to circulate the refrigerant in the system under pressure.

While the compressor does all the heavy work, the properties of the refrigerant is what produces the cooling effect in the air. Single-stage works at one level only: 100% capacity or High, while the two-stage AC operates on two levels: Low or 60% to 80% (depending on manufacturer) of the maximum, and High or 100%.

One Stage Air ConditionerTwo Stage Air Conditioner
Compressor has one level of operation: HIGHCompressor motor has two levels of operation: LOW & HIGH
Cools your home at 100% capacityRuns at a lower speed and takes longer to cool
Price: $2500-$3500Price $4000-$5000
Repair cost: LowRepair Cost: Moderate to High
Basic and easy-to-find parts for repairs and could be performed by most HVAC techniciansComplex technology with harder-to-find components. Few technicians are trained to fix and maintain
Less prone to breakdown and mechanical problems due to simplicityMechanical problems more likely due to complexity
15-25 year lifespan7-12 year lifespan

It’s important to understand how single stage and two stage air conditioners differ before deciding which type is appropriate for your circumstances. Many people may be buying an air conditioner for the first time – but once you’ve had a bit of experience purchasing units you might not want to be enticed by promotional offers that aren’t really going to get your home more comfortable.

Imagine that you’ve just moved into a new home. You’re probably not thinking about how long your appliances will presumably last in your house – but appliances like an air conditioner tend to stay with you for years. You want to make the right choice.

If you’ve had an old air conditioner and it recently broke down, you may be thinking about purchasing another one of the same type that you already have. You might do this because it lasted a long time, or because your current AC was adequate and you were happy with its performance.

On the other hand, if your previous air conditioner broke down sooner than expected, you may want to explore air conditioning options that weren’t available when you last bought one.

Whichever your situation is, you are making the right move by doing research first. Be careful though: Most websites or so-called AC “experts” will merely advise you to purchase a more expensive unit which in this case is a dual-stage air conditioner. It is still up to you to make the decision based on your individual needs and more importantly, your budget. 

Let’s start diving into the three most vital factors to consider when purchasing either a single-stage or two-stage air conditioner.

Factors to Consider When Choosing Performance Air Conditioners

Cool and Comfort

A Single Stage air conditioning unit is cooling your home at one capacity: high. This is perfect if you want to quickly get to your desired temperature level as soon as possible, perhaps on a really hot and humid summer day when you walk into your house. It will stay on until it reaches your thermostat setting, and then cycle off automatically only to turn back on once the ambient temperature gets warmer again.

Two-stage air conditioners are considered performance air conditioners and work differently. A two-stage air conditioner’s compressor starts in the Low setting, which is equivalent to 60% to 70% of its maximum. This setting suits for milder weather days when you don’t need as much cooling. Most of its running time, the setting is on Low so it runs longer and reduces the starts and stops of the unit.

Once it gets too hot outside, this unit will crank up to High, equal to the 100% capacity of a single-stage air-conditioner. It will stay that way until the thermostat in the room is satisfied.

Affordable Pricing

A single-stage air conditioner is significantly more affordable than the two-stage air conditioner. The two-stage air conditioner is more state-of-the-art and complex so the upfront price, labor cost and additional installation charges are significantly higher than the single-stage AC unit.

A single-stage air conditioner in the mid-efficiency range can cost $2,500 to $3,500 including installation, while high-efficiency models can cost $4,000 plus for the hvac equipment and installation costs.

On the other hand, in its mid-level efficiency, a two-stage air conditioner costs between $4,000 to $5,000. While the high-efficiency two-stage units can cost you between $5,000 to $7,000 to purchase the unit and have it installed, not yet including the needed add-ons such as a variable-speed air handler or furnace.

Potential costs such as repair and maintenance of a single-stage and a two-stage air conditioner are also very different. Because of its more complex design, two-stage AC naturally has a larger number of parts and they are not always easy to find in stock. Obviously, the labor cost for repair for the two-stage unit also is higher compared to single-stage.

HVAC Energy Consumption

Since a single-stage air conditioner cools your home at a full blast, it can do the job of chilling your home quickly and will automatically turn off once it reached the thermostat setting. This could mean that there is a considerable amount of energy consumed in starting up and turning off the furnace during the day.

The two-stage air conditioner, however, will consume lesser energy since it takes longer to run and there are fewer times for it to turn on and off.

What most sources will not tell you is that two-stage cooling is not ideal for every home, specifically for larger residences, unless you have a zone system which further complicates the HVAC system.

A house with this kind of system makes it easier to control the temperature in each zone or room individually. Without this, stage one of the two-stage AC blower speed will most likely be insufficient to push the cool air to all places in your home. Unless you’re willing to purchase more than one two-stage unit for example, which by the way, is undoubtedly more expensive!

Why Single Stage Is Better Than Two-Stage Air Conditioners

Most homeowners decide to purchase a single-stage air conditioner because it is more practical for their needs. The number one reason is that the up-front cost is lower.

The second factor most people consider whether to choose a single-stage air conditioner over two-stage AC is the size of their home. A smaller to an average residence can effectively be cooled by just a single compressor. It’s worked well for 50 years. If it ain’t broke, don’t fix it. You’re just trying to cool your air.

Lastly, but not the least reason why single-stage is more reasonable, is the potential cost of repair and maintenance. A single-stage air conditioner’s ease and low cost of repair is a huge advantage.

More complicated equipment such as a two-stage air conditioning unit will definitely have more expensive parts. And these HVAC parts are not always easy to find at local distributors.

Getting them delivered from bigger out-of-town branches may take time and additional courier charges. Let’s face it, one of the last things you want to hear when it’s blazing out and your AC is down is you have to wait for parts. This rarely happens with a one-stage AC.

Accompanying this problem is looking for a trained technician to fix the two-stage air conditioner. Since it is more high-tech than your regular AC, only a few expert mechanics can understand and repair its issues. And since he may be one-of-a-kind in your area, you may be charged more than your average repairman.

What about the Variable-Speed Air Conditioner?

If you are looking to buy an even more lavish and high-tech air conditioning unit than the two-stage air conditioners, you may want to consider variable-speed air conditioners. Why is it pricier? While the two-stage air conditioner runs on Low at 60% to 70% of the maximum power, variable speed can run at much less capacity: 25% to 30%. This results in longer cycles that can almost last a whole day during the summer season. 

One advantage of this variable-speed air conditioner is it promises better dehumidification of the air in your home. It claims  greater comfort at a lower utility cost.

Any drawback? The amount of needed air conditioning repair of course. And since it is an upgrade to an already expensive two-stage unit, an average variable speed air conditioner ranges from $6,000 to a whopping $10,000.

Single Stage vs Two Stage Conclusion

Don’t get sucked in to all the marketing. When the weather turns warm and you’re in need for a new HVAC system, don’t focus too much on heating and air options. Your main decision is to choose the right contractor. Nothing is more important on the installation of a new HVAC system.

A good contractor will determine the cooling needs of your home and help you find the right type of AC that will cool your air perfectly. And the right AC will probably be the less expensive option.

Take that extra money for a two stage AC and buy a better thermostat or air filter or when you get a new system. Those can improve indoor air quality and you’ll be much happier with that kind of upgrade.

You will be happy with any single stage model as long a quality contractor handles the installation. And they won’t recommend features that you don’t need.

21 thoughts on “Single Stage vs Two Stage Air Conditioner | One Should Be Avoided”

  1. Hello,
    Enjoyed reading your article. I have an interesting conundrum that my local AC dealer can’t explain. I have a brand new Trane, two-stage, compressor unit, gas pack on my roof, that I hate already. What I hate about it is in order to get the humidity out of the air in my house. I have to run it around 75 to 76° and I’m old and can only stand about 80° as a low.
    What happens is when the unit kicks on, I smell dampness blowing until the first stage kicks in but then when the first stage transitions to second stage I smell the dampness coming out of the vents again. I live in Tucson so it’s not very humid so I’m not understanding, the damp smell. I don’t smell the damp smell when the compressor is blowing in first stage. Thanks for listening.

    • Funny smells can be tough to track down. And it’s difficult for me to say anything definitively without a thorough investigation but it’s not uncommon to have a damp smell from an air conditioner especially if there are certain issues. But you being in Tucson eliminates many moisture issues due to the dryness of your climate. Since it’s a new unit, I wonder if you’re picking up smells from the equipment or new materials. Some have noticed the smell from glues, sealants, insulation within the equipment, etc…. In second stage, the air conditioner will move more airflow so it could be more pronounced because of that increased speed of the motor. There is an air cleaning device I have used in the past that has helped with smells you might want to try called the Reme Halo.

  2. Robert — Your points all make good sense. But a single-stage unit has not worked well in my perhaps unusual situation. I have a 70-year old 1-1/2 story cape cod, with ducts built for heating only, and that with older high-temperature furnaces using low air flows. I’ve calculated my first floor to have a 2-ton cooling load, and the second floor to have a one-ton load (brick walls facing sun with no insulation). So I’ve had a 3-ton single stage unit for many years now. But I use my second floor only for storage and keep it’s ducts closed off. And my 3-ton unit is way oversized for just my first floor, and it short cycles too much. So I’m not sure whether to next get a 2-1/2 ton single stage, which one tech said would be neither here nor there, or to get a 3 ton 2-stage unit, and perhaps wire it to keep the blower on high in both stages if I ever start using & cooling cooling the 2nd floor–unless that would hurt the humidity situation too much. Each tech to visit has a different recommendation. I’d appreciate your thoughts. Thanks!

    • Hi Steve – Your situation is indeed complex, and I understand the challenges you’re facing. It’s clear that you’ve thoughtfully considered various factors, but let’s delve into this a bit more.

      As you’ve rightly noted, oversizing an air conditioner can lead to short cycling, which can decrease efficiency and increase wear on the system. An air conditioner’s primary job is not only to cool your house, but also to remove humidity. If the system is too large, it will cool the house quickly, but it may not have enough time to properly dehumidify the space.

      Not to make it the picture muddier, but I would say the size of the air conditioner or how it’s staged isn’t nearly as important as getting your ductwork sized correctly. Poor ductwork can severely hamper even the most efficiently rated HVAC systems. In fact, a two stage air conditioner can be much more susceptible to problems with airflow than a single stage AC.

      Making sure your ductwork is properly sized, sealed, and insulated should be your first focus. When you find a contractor that mentions that, then you’ve found the right contractor.

      In the end, there are many variables at play here, and it’s hard to give a definitive answer without a thorough on-site evaluation. A good HVAC professional can conduct an in-depth load calculation and ductwork evaluation, considering factors such as insulation, window size, and local climate. They can then recommend the most appropriate solution tailored to your specific needs.

  3. Very helpful! Our upstairs unit died. When we returned from being away a couple days with a dogsitter at home running the ac upstairs, the line from the condenser outside to the ac unit inside was lined with ice! Since it was 90 degrees outside one contractor said imagine how much energy was required to keep it frozen! When we turned off the ac and ran just the fan as instructed, it rained water into the house as it defrosted draining mostly into the master bedroom!

    We have decided to replace the 15 year old Carrier ac since we had already added freon before and it was 4 pounds down. I will now go with a single stage a/c per your advice. We want something bullet proof. Thank you!

  4. Hello Mr. Bradford: I currently have a high-end Carrier variable speed HVAC. I do not know if both the heating and the AC are single stage or dual stage (I think dual??) It is still going after 14 years, but I am advised that it is old and declining (as am I!!) I now have 3 zones and like that. One contractor has offered a Carrier – 3.0 Ton 16 SEER 80 AFUE Gas Heat Split System – Two-Stage Furnace (I assume a one- stage AC.?) It has 2 zones that do no communicate with each other. The other contractor proposes a Trane-3 ton- 2-stage AC and one-stage furnace. It will also have two zones that do not communicate with each other. They are very close in price. I have read your article several times and it says that a two stage AC is “not as good for large homes UNLESS they have a zone system.” I do like the zone system. But is my home of 1840 sq ft on two floors considered “large”? Meaning I should NOT pay extra for a two stage system? And are more stages better for temperate zones (I’m in NC)? And is it more important to have two stages for the AC than for the heating? Or do I need both as two-stage? I am sooooo overwhelmed trying to make this decision. RJP

  5. My home is 2000 sq ft. I have a gas furnace. The current hvac is Heil which is 27 years old. I know it’s just a matter of time on replacing it. I’m convinced on the single stage unit but do you have any recommendations on brand,Seer rating and ton size? Thanks.

    • As it turns out, theres no quick answer for your question Joe. But as far as recommendations for brands I’d suggest you read this article: Wonder Which Air Conditioner Brands To Avoid? 1 Big Mistake People Make

      SEER and tonnage is best decided by working with a good quality contractor. There are several factors that will influence the appropriate choice for your home. One tip I’ll give you…the contractor that recommends a smaller tonnage air conditioner is usually the one to go with. The guys that guess, always guess high. Since they’ll be outnumbered, the ones that do the work to calculate the correct size will look like they’re putting in too small of an AC.

  6. Thank you for clarity. You wrote this article a year ago. But I was just waiting for it to make my decision. I have been troubled by every other article saying two-stage compressor is better. They tout about saving money in electricity. But how significant is that considering that a two-stage will be running for more duration.

    Thank you.

    • Hi Sudhir – It’s true that two stage units will run longer but they do it while using less electricity. In that way it will save a small amount of money in lower electrical usage. But as I mentioned in the article, the big problem is that saved money will quickly disappear. The cost of repair and the shorter longevity on a two stage air conditioner will cost significantly more. A single-stage air conditioner’s longevity, reliability and low cost of repair is a huge advantage.

  7. Thanks. I learn so much from reading the information you gave on the HVAC stages.
    Question: I just bought a newly built Cando. Have an American Standard BAYHTR1505 BRKC.
    it says: Supply Volt: 208-240, 60 Hz. is this a Stage 1 or Stage or 2 . I am trying to
    find it in the manual. It has a Honeywell Home Pro Series thermostat. I am wondering if
    this thermostat is compatible due to my observation of how it is heating and cooling the

    • Hi Sylvia – I’m glad the article was helpful. As far as your question…the model number you have is for an electric element add-on for an air handler. Based on that, I would say you probably have a heat pump. It’s very common to have electric elements as a backup heating system in case the heat pump breaks down or if it needs help adding more heat to the home.

      Since you mentioned your condo is newer and you probably have a heat pump, I’d guess you do not have a two stage heat pump. They rarely use “high end” equipment in new construction.

      That being said this is where it will get confusing…because you have a heat pump AND a backup source of heat (electric elements in the air handler) you technically have a two stage system. But this style is different from what was explained in this article. It’s not two stages in the heat pump. It’s considered two stages because there are two sources of heat. Hope this answers your question and isn’t too confusing.

        • A small number of parts are interchangeable between single stage and two stage air conditioners. But the majority of parts in a two stage air conditioner are specific to that style of equipment. Some are even brand specific which makes them even harder to track down in case of failure.

  8. Robert,

    Greatly appreciate you sharing your knowledge and expertise. Your information was very helpful. I have a small home and wanted a good unit but was concerned about falling into the technology trap (two stage/variable speed) and buy something that really wasn’t going to provide any material benefit and cost more to maintain and repair overall. Thank you!

  9. Robert, thank you for posting this. I thought I was sold on a two stage, but no one can quote me one or get one. I’ve had a Trane single stage scroll compressor for 23 years before it gave out. Now I’m satisfied with going to a single stage again. Thanks~!

    • Glad this helped. The more complicated the air conditioner, the more trouble they’re having with production. Imagine what it will be like when the AC breaks down the road!


Leave a Comment