When to Install a Ductless Air Conditioning System

What’s the Difference Between a Ducted and Ductless Air Conditioning System?

Air conditioners provide cool air through two forms of delivery: ducted or ductless systems. The majority of homes in the U.S. are built with air ducts made from sheet metal that run from the main air conditioning unit to each room in the house. The ducts are hidden in walls and air is delivered to each room through vents. In ductless systems, the refrigerant from the outdoor condensing unit is sent directly to an air handler located on the wall or ceiling of a particular room.

While a ductless system can have several benefits, many homeowners with existing ductwork will be better off from a financial and comfort perspective by using a ducted system.

Benefits of Ductless Air Conditioning System

  • Easy for a contractor to install (no ductwork)
  • Some flexibility in location of air handler
  • Ability to cool the home by specific zones
  • Quiet when operating

Concerns with Ductless Air Conditioning System

  • Reduced overall indoor air circulation and increased humidity can lead to comfort and air quality problems
  • Appearance of the air handler on a wall or ceiling in each room
  • Higher cost of ownership for a whole-home solution if your home already has central AC
  • External refrigerant lines which could cause energy losses and aesthetic concerns
  • Serviceability and ease of repairs could be a problem as the unit gets older

When to Consider Installing a Ductless Air Conditioning System

While we don’t recommend a ductless system for most homes, there are several situations where a ductless system should be considered over a traditional ducted one. These include:

  • Room additions or adding cooling to a garage or work space
  • Cooling smaller, older homes without existing ductwork
  • When space is at a premium and ducts won’t fit
  • When replacing a less efficient window/room air conditioner

The bottom line on Ductless Air Conditioning Systems

Your comfort, humidity and long-term reliability should all be factors in making a smart decision. As with any important HVAC question, it makes sense to talk with a professional. Contact a reputable licensed contractor who can explain the many options and variables when it comes to selecting the best solutions for your needs.

If you’re considering a ductless system, comment below and tell us some of the reasons it appeals to you!

For more information on ductless systems, click here.


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29 thoughts on “When to Install a Ductless Air Conditioning System

  1. Hello – I have a bilevel home with a one zone central air. The downstairs family room is not keeping as cool as in previous years. I had service performed and they do not see any issues with the unit. They said it may be an issue with vents but do not see anything on the surface. Would you recommend us upgrading to ductless or upgrading with ducts. I assume with ducts they would need to tear holes in walls/ceiling.

    • Here are a few thoughts. Has the load changed on that space? This could be caused by adding or removing doors, walls windows, etc., or removing shade trees, changes in insulation (settling) among other things. If the load has changed (increased) then you might need more capacity (a larger system) to keep up with changing demand. If it continues to be a problem you could add a small mini-split to the space that needs additional cooling and keep your whole home system as well. This is a pretty common practice for people with spot cooling needs. Hope this helps.

  2. Hello,
    I really need your advise.
    I’m a teacher who works in a small enclosed space with no windows and an extreme heat. Our scool is old and
    A/C unit doesn’t work. If other rooms have windows, my small enclosed space doesn’t. What should I do to relieve my and my students’ suffering? I’m thinking about a small portable unit without the hose and any connection to window.

    • Hi Tanya – The first thing you might want to do is ask about proper ventilation to and from that space. Being in an enclosed space is ok as long as you have proper make-up air which should also help you regulate the temperature. If you only have a vent coming into the space and no return air vent then they are assuming you are leaving the door open so you can use the vents in the hallway or in another room nearby. You might try moving more of the hot air out of your space by putting a box fan near the doorway to move the hot air out into the hall. Once you figure out the airflow situation you can then move on to finding the controls for the air temperature coming into your room in the hope that you can regulate it. If that is unsuccessful, maybe you can regulate the incoming air by partially blocking the vent coming into your space. Portable AC units might work. Other mini-splits or through the wall units will require modifications to the walls but these might offer a more permanent solution, albeit at higher cost. I hope this helps. Thanks for visiting our site.

  3. I have a brick twin house in PA. It was built in the 1920’s and does not have any duct work. Our heating system is a boiler with radiators and we have to use window AC units in the summer. Would it make more sense to keep using Windows units or to get a ductless system installed?

    • Hi Mark – I will base this answer on most of the posts we have seen on this site and some of my own experience. In general, mini-splits can represent a large improvement over window units for many reasons (window access, efficiency, heat pump options, etc., to name a few) but they are more expensive than window units and not really a DIY solution for most people like window units can be. Central systems in turn offer some benefits over mini-splits (better air circulation and filtration, better humidity control, no units hanging on the walls, etc) but getting ductwork into a home that has none and has boiler heat can be a trick too. I put central AC into my 1920’s home with boiler heat and the cost was actually less than the quotes from the mini-splits. I had to put the air handler in the attic and gave up some second story closet space to run ductwork to the first floor from the attic but I have been happy with that solution.

      For cases like this we usually recommend getting a few different quotes for both central ducted and mini-splits and before deciding. You might also consider just adding a zone at a time or using a mix of central, mini-splits and/or room air for different locations. Maybe a small central system combined with some mini-splits in key, hard to get areas might be one option. Bottom line is that it takes a while to get different contractors to look at unique jobs like this until you find one that is on the same page as you on the job so plan on that. As we are nearing the end of the cooling season (I hope) you should have time to do this research. I hope this helps answer your questions. Thanks for using our site!

  4. I had never heard of this system. I have an older motor home that needs an ac replacement and with interior fans, wouldn’t this be a good alternative to installing a new ducted ac?

    • Hi Elsa – a mini-split might work on a mobile home but it would not be very “mobile” if you have to move it. The outdoor unit usually sits on the ground outside the home but you might be able to attach it some other way. There are some other specialized mobile home HVAC systems you might want to consider as well. I hope this answers some of your questions.

  5. Hi Kay – options for this small space in an arid location would be, in order of increasing cost: “window” or “room”” AC installed in a window in the room – you can buy at a local retailer and probably install it yourself or have someone do it for you. The next would be a through the wall PTAC system like you see at hotels. this is a little more expensive but you get to keep your window functioning without an AC unit sitting in it. The next step would be a mini-split system with s separate outdoor unit and the indoor cooling unit hangs on the wall or in the ceiling. Both the mini-split and the PTAC would require a good contractor to size the unit and handle the installation.
    I hope this helps to answer some of your question.

  6. I would like to buy an a/c unit for my parents who live in the high desert of NM, it is extremely dry, there is no humidity to speak of. They do not have central A/C and need to cool a room with unfortunately high ceilings (but with a ceiling fan). They will not want to run an exhaust hose out the window; but do they need to? Please advise me on what’s best–10,000 btu, portable unit? That is what I’m thinking unless you have another suggestion. Many thanks.

  7. My name is Michael Brooks.I want to know if you can get me this Air Conditioners to purchase without installation.

    4 ton 410-A 14 seer condenser

    4 ton 410-A coil

    50 foot 7/8 lineset

    Kindly send me the pricing plus tax for the above material .Also let me know the major credit cards you accept for payment.I will look forward for the pricing.I need your contact details in case of any future reference.Also let me know if you sell water heaters.


    Michael Brooks

  8. I didn’t realize there were external lines with a ductless system. That seems like a deal breaker to me. My wife and I are building a home and working on the plans. It seems like zone-specific cooling would be really nice, but I don’t want to lose curb appeal. Thanks for the information.

  9. I have a sun room. Home built in 1928 CA. II asked for bids for a split unit.
    contractor 1. Mitsubishi # MSZGE36NA-8 17,200BTU & #MUYGE36NA1
    contractor 2. Mitsubishi # MSZHE24NA & MUZHE24NA (18 seer)
    space about 2000 sq ft.
    What is the difference between SEER and BTU. Which is more important?
    Contractor 2. Has also quoted for Mitsubishi 19 SEER high efficiency 2 ton heat pump system. And 14.5 SEER 3-ton pump system.
    Totally confused.

    • Hi AJ – here are a few things to consider.
      SEER (Seasonal Energy Efficiency Ratio) is an efficiency rating. This is a rating based on an average load over a typical annual season of operation – weighted by the amount of time spent on “high load” –e.g. imagine the hottest day of the year in the afternoon and the time spent running at night and in the fall and spring. The efficiency varies based on these load conditions so the DOE has selected a weighted average range for the US to judge/rate various systems. Higher SEER systems usually cost more than lower SEER systems for the same capacity (BTU/Hr).

      BTUH (BTU per hour, or British Thermal Units, or “tons”) is a measure of capacity or how much space the equipment can cool (along with adjustments for things like your insulation, shade, leaks, R value of windows, door, etc.). Larger capacity systems usually cost more than smaller systems.

      One really important thing you and your contractor need to consider is how much capacity (BTU/Hr) you need. If you get too much capacity you will not have enough run time to keep the air moving in your space and you will lose the benefits derived from keeping the air moving across the cold coil to remove humidity and across a filter to remove pollen, debris and other contaminants. Conversely, too many BTU’s will yield short run times and poor air quality. If you size it too small, your system will not keep up on the hottest days.

      Good contractors can do calculations to spec out the size of your unit to match your needs. If they don’t do calculations or do them poorly you might have worse air quality and humidity problems. A variable capacity system (with variable refrigerant and air flow) might be a little more forgiving but the principles are the same. The capacity needs to be right for the worst day as well as the light load conditions. Good contractors should be able to explain this to you.

      BTW, Efficiency ratings like SEER are simply measures of how much energy it will take to cool your space. The ratings are comparable from one system to another based on the standard testing procedures. Generally higher SEER ratings will yield improved electric energy savings depending on how you run the system. For example if you have a high SEER system and have a hot summer and keep the thermostat really low you will burn through a lot of electricity. If you have a lower SEER system and have a cool summer and keep the thermostat high for extended periods you might use less electricity. High SEER does not always mean lower operating cost. Energy costs also depend on how you operate it.

      On this site we recommend getting 2-3 quotes from various qualified contractors who do the right calculations and recommend good options for your space. Find someone who can explain all this to you and help you make the right decisions. Here is a link to a contractor organization we support and has a contractor locator app.


      It is a good if you can find a contractor who is on the same page before deciding. It might take a while but our research shows you will be more satisfied with your system decision if you are satisfied with your contractor doing the installation/service.

      Good luck with your HVAC project!

  10. Thanks for the helpful blog and forum – lots of useful information here. We decided to convert our garage into living space recently so needed to decide on an HVAC system. I am a general contractor so I have been involved with the placement of various types of HVAC equipment in lots of homes. I figured that a ductless mini-split heat pump would be the easiest and cheapest to use but all the quotes that came in for mini-splits were about the same as the ones I got for adding a small central AC/heat pump system with the air handler and ducts in the rafters above the space. The ducted system was actually cheaper than the ductless after all said and done… $4600 for the ducted system and $6k+ for the ductless.

    We did not have a lot of space to mount the wall units anyway and running condensate lines in the ceiling was difficult to due to the space available. It gets humid here in the summer and I had heard a lot about mini-splits not dealing well with that so I went with the conventional HVAC and have been happy with it – good air flow and no issues with humidity. Also, visually it looks a lot nicer than having the ductless unit on the wall and this is probably better for resale… since it looks cleaner and more like what people are used to having in their homes.

    We set the air handler at the end of the attic space and ran insulated round, hard air supplies around the outside edge of the attic to maximize storage space and also to maximize filtered air flow from the air handler. Also, with mini-splits, each ductless unit has its own condensate drain line to run outside, so with just one central air handler we only have to worry about one of them getting clogged up over time and spilling over. We installed a pan with a drain tube and pan switch that sends a message to the thermostat to turn off if there is any blockage in the drain tube.

  11. Hi Chris – most split systems (both mini-split and ducted) and window/room AC units have a drain the runs from a drain pan under the cold coil, allowing the condensed water vapor to be discharged outside of your home or into some sort of drain.

    I am not really familiar with portable AC units but if they don’t have a drain or some sort of collection device (like a dehumidifier) then they might be using the moisture to cool the condensing (hot) coil – but this would just re-evaporate the moist air into the living space, thus not doing much for any humidity you have there. If you live in a humid area you might want to research this more.

  12. What do they do with the water that naturally is pulled out of the air via cooling the air? Is it put back into the air some way? I’ve seen an ad for some small portables that use the condensate to cool the coils.

  13. I have an older 2 bedroom home built in the 1930’s, roughly under 1000 square feet with no existing ducts. The house is heated by a boiler system & cooled by a window unit. I was quoted a few years ago that it would be over $12000 to install central air & it would be difficult to run the duct work. Would I be better off going with a ductless system? Thank you.

    • Hi Carla – I have a home built in 1920 that had no ductwork and baseboard boiler heat. I got quotes from contractors for both ducted and ductless systems. We finally found a contractor who came up with a way to put the air handler in the attic and run flex ducts to the second floor in the attic space and get air to the first floor by running ducts through the closets. We gave up some closet space (not a small concession in an older home) but we got system that cooled the whole home for a fraction of the cost for a multi-room ductless system.

      There are many posts on this site about the pros and cons of ducted versus ductless system which you can read. It is difficult to generalize but basically, you get better whole home air flow and filtration with a ducted system along with better humidity control (if you are in a humid area this can be important). Ductless gives you the energy cost benefits from room by room zoning (if you frequently close off large sections of your space) along with better efficiency than window/room AC. We encourage homeowners to get quotes from at least three different contractors for both types of systems before deciding.

      At 1,000 square feet with no ductwork it is quite possible the move to mini-splits will give you cooling benefits over your window units and you might even get some heating benefits if you get a heat pump model. Still, you might get a few ducted quotes just to make sure you are making the right decision for your home. Good luck with your HVAC project!

  14. every manufacturer should send a installation manual with product so customer can satisfied himself that manufacturer,s technician perform his work up to mark.

  15. It’s a good piece of article sharing information about when can we install a ductless air conditioner. Really appreciate the points on the benefits of installing ductless air conditioner. The advantages are numerous and the installation options for homeowners are significant.

  16. I live in southern Ohio. I have a heat pump/central air system that kills my wallet during the winter months. The house was built in the 1960s and I don’t want to invest as much money as needed to go Geo-thermal. My last electric bill was over $500.00. I have been considering going to the ductless mini split system when I have to replace my existing unit. Can a ductless system handle the cold Ohio winters and provide enough cooling during thr hot summer months. Also, if I install a ductless system do I have to have all the old ducting removed. I don’t see why I couldn’t leave everything else in place, all it would be doing is taking up space.

    • Gene – There are a lot of options for HVAC replacement you can consider beyond just the premium geothermal systems and, depending on the size of your home some of the lowest cost options will involve continuing to use your existing ductwork and simply replacing your old central HVAC system with another central HVAC system. People usually only go away from a ducted system if they have some fairly specific reasons for doing this like having poorly installed and leaky ductwork and/or a compelling need to supply HVAC to individual rooms or zones which you can get with ductless mini-split systems. But in answer to your question, in these cases you could leave the ductwork in place but you might want to seal it off. You could also leave your existing air handler in place along with the new mini-splits and just use it as a whole house fan and filtration system to circulate and clean the air by just running the fan only, or you might be able to keep it as is and use the old system as a backup in case your mini-split additions are not keeping up. All system types should keep up if they are sized properly for your home but sizing decisions are not always an exact science.
      As for your geographic location, all heat pumps work better on days that are not severely cold, like below 15F. If you get below that point your heat pump (whether it is a mini-split or central style) will probably be using auxiliary heating methods like resistance heaters which are usually not very efficient. What some people are doing in colder climates in the upper Midwest is installing a “dual fuel system” which is a heat pump with a standard gas furnace but the gas furnace only comes on when the temperature gets really cold. Most of the time, when the temperature is above 15F the heat pump will be the primary source of heat. A side benefit to dual fuel systems is that you can also decide whether to run the heat pump on electricity or gas depending on which has the lower energy prices at that time.
      There have been a lot of improvements in the efficiency of central HVAC and heat pump systems over the past few years so if your system is older you might look into just replacing it with another basic system and you will probably realize a nice energy savings without going to a premium geothermal system or going to all the cost of installing some number of new mini-split systems to cool and heat various rooms in your house. Instead, you could install another heat pump or a standard central AC unit with a standard gas furnace or the dual fuel system mentioned above. If you ask a few local contractors to quote various systems they can also estimate how much energy you will be saving with each type they are quoting and they can even quote some higher efficiency models if you really want to save on energy.
      You can really learn a lot from talking with a few contractors about these options but you have to ask. Most contractors are familiar with all the technologies mentioned above but if you just ask them to quote just one type that will be what they quote and you will have no way to compare these different options. I hope this answers your questions but there are some other articles on this site that go into more detail on this topic. Here is a link to one of them.

  17. I have concerns with installing one in a small condo in Myrtle Beach right at beach front with the humidity??
    Not sure if ths will work well being in this constant ocean air climate.

  18. The short answer is yes. Some people have used ductless mini-splits in conjunction with a central AC system. Typically, the ductless mini –splits are used in the more remote areas or rooms that are used less frequently or might be located far away from the central AC system – e.g. an attic space or “bonus” room that is frequently zoned off from the rest of the house or used only occasionally.

    Depending on the size or the layout of the house you are planning, you should also consider two central systems – usually one for the upstairs and another one for the downstairs. This way, you can adjust the temperature up or down in those areas independently and reduce your overall energy consumption. For the areas where people will be sleeping at night I would also consider a central system with some sort of capacity modulation – either one with two steps of capacity or continuous capacity control along with a variable speed or stepped indoor air handler. This will be especially important in Houston because of the comfort and health problems associated with humidity control are almost as important as the temperature control. If you go with a capacity control system, usually 16 SEER or greater, the system will be able to adjust to the load on humid nights when you need the system to run at low capacity for a pretty long time to make sure the humidity is removed and the air remains fresh and filtered. The same system can still run at the full load capacity during the day when the demand for cooling is most critical. The other benefit of these systems is that they are really quiet when they run at the low capacity mode. I have a two step system and I can barely hear it when it runs at night on low load.

    I really appreciate your posting this question. I know investing in a new, custom built home involves a lot of decisions and unfortunately the HVAC decisions are sometimes overlooked. In a hot, humid area like Houston it would be good to consider the comfort and energy cost factors as well as the many other decisions you will be making. Good luck with your new home!

  19. I will be building a large house in Houston TX., On occasion I will be home alone and will not need to cool the entire house.
    My question is have you heard of a residential application of both Central AC and Heat combined with a ductless system. .

  20. I will be building a large house in Houston TX., On occasion I will be home alone and will not need to cool the entire house.
    My question is have you heard of a residential application of both Central AC and Heat combined with a ductless system.

  21. Are there any ductless units that remove the humidity? It would seem to be a simple process and require only a small drain tube to go through the wall along with the pipeset and power.

    • Ned,

      Most common units do have this feature that allows the condensate to drain externally, like you suggested. The real drawback with Mini-splits is air circulation. Ductless systems don’t seem to circulate the air throughout the house as a more common ducted system would. This limited circulation leads to a lower “comfort” level when comparing the ability to control whole house humidity to a common ducted system.

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