Four Myths About Ductless Mini-Splits

Frank Landwehr
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Mini split in room near ceiling

Understanding the Pros & Cons of Ductless Mini-Split AC Systems

Over the past few years we have all observed the U.S. HVAC industry’s fascination with ductless “mini-split” air conditioning systems in the U.S. Recent HVAC trade shows have been crowded with OEM’s promoting this “new” way of providing home comfort. National advertising and media/public relations tactics would make us think it is just a matter of time before we all say goodbye to our central AC systems and get with the rest of the world (i.e. Japan, China and Europe) in the way we keep our homes and businesses cool and comfortable.

The article below was written in 2013. We have updated information for homeowners busting myths about ductless mini split systems, outlining what to consider when choosing a new HVAC system, as well as recommendations on when a ductless system might be right for your space.

The AC & Heating Connect staff has also conducted research on ductless systems and uncovered some facts that might be of interest to contractors and distributors as the industry plans for the future growth of this segment.

Myth #1 – The sales of ductless mini-spit systems continue to grow and will dominate the U.S. market in a few years.

Industry statistics would not support this statement. While the ductless segment has posted impressive growth rates in the U.S. since 2005, the growth rates have been slowing recently and the largest ductless segment (small, single evaporator systems) have not grown at all since 2010. These sales remain stable at about 260,000 units per year, or only about 4% of total unitary AC shipments. Some larger VRF-style commercial systems continue to grow at higher rates, but their numbers in the U.S. remain small at only 28,000 units per year.

Myth #2 – Ductless mini-splits are ideal whole-home HVAC solutions in the U.S.

The current economic facts about ductless simply do not support this claim. The installed costs associated with using mini-splits to cool and heat an average 2,000 square foot home with ductless mini-splits would cost almost three times the cost of simply replacing your central AC system with another ducted system. Even in a home where you had to provide new ductwork for the central system, you could still expect to spend about 50% less on a typical central AC system installation versus the more expensive ductless options.

Myth #3 – Ductless mini-splits are more energy efficient because there are no air leaks in the ductwork.

What people who make this claim fail to mention is that in ducted homes, which have poorly installed and leaking air ducts, the conditioned air is probably leaking out of the ductwork but it is going into the conditioned space somewhere and helping to keep the house cool. In those cases the cooling energy is really not lost to the homeowner. While mini-splits don’t have duct losses, they do have other losses. Instead of distributing conditioned air throughout the home, mini-splits distribute refrigerant. In many cases these refrigerant lines are run outside the conditioned space and in these cases there are thermal losses associated with energy transferring from those lines to the space outside the home. A legitimate energy loss occurs when you are heating or cooling your backyard with mini-split refrigerant lines (see photo below). Duct leaks that leak into the conditioned space are not really losses at all unless they escape to an unconditioned space. The other claim made by mini-split advocates is that they provide energy saving due to “zoning” or shutting off energy use in unoccupied rooms. What they fail to mention is there are other modern methods to zone off rooms besides using ductless methods. There are many ways to achieve zoning.

*Discover the updated status of this myth here.

Myth #4 – Ductless mini-splits provide superior comfort and quality of life.

The problems with ductless cooling are not well understood by many U.S. consumers since they are relatively new to this region. The typical comfort experience with mini-split systems could provide a real challenge for American consumers who are used to central AC systems with good airflow exchange, filtration and humidity control. Cold and hot spots are also common with ductless systems due to the spacing of the indoor units. In addition, there are concerns about US homeowners’ reaction to the aesthetic and architectural impact of having air conditioning systems hanging on several interior walls and having refrigerant lines running to various rooms on the sides of their homes. Before installing a ductless system with multiple evaporating units it might be good to show your customer some photographs of some of your previous mini-split installations so they have proper expectations.

*Discover the updated status of this myth here.

The Bottom Line on Ductless Mini-Split Systems

Ductless mini-split systems are ideal for spot cooling situations in homes and businesses where ductwork is either not available or difficult to install. It is important for contractors to have these systems in their portfolio of HVAC solutions for certain situations and learning where and when to recommend them is essential. Knowing the facts associated with these new systems is also essential to avoiding problems when customers are surprised by the many “myths” about this technology.

The myths in this article have been reevaluated. You can find the updated article here.

What has your experience been with ductless mini-splits? Leave us a comment below!

A typical indoor wall-mounted, evaporating unit – usually one per room are required to minimize hot and cold spots.

A typical U.S. style home is shown here with a retrofit mini-split system. Notice the exterior line sets and condensate drains. Thermal losses could be expected from the vertical, external refrigerant lines and these might cause the system to have trouble keeping up on really hot days. Also, notice that the window-room air conditioners have not yet been removed. A close up photo of the house above, showing the external refrigerant lines and a condensate drain line. Ductless mini-split systems are often used to cool room additions as shown here in the garage area. A large, high rise apartment building is shown, using many mini-split systems – one or more per apartment.A large, urban apartment building is shown, using mini-split systems – one or more per apartment.

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538 thoughts on “Four Myths About Ductless Mini-Splits”

  1. My gut feeling (usually right) the ones against ductless are apt to lose $ in their connection to the AC business. Always follow the $ trail it will always lead you to the truth, unfortunate but true.

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  2. Very helpful response. I had the four ton unit replaced with a 5 ton 2 stage slit system, and had a return cut into the ceiling in the media room. The room is comfortable and the extra air is a huge benefit to the other area of the home as well. The old unit was 23 years old…it had a good run but I am glad to replace it on my terms rather than waiting for it to go out at a bad time. Thank you again for your response. I decided against the mini-split system. If I had a bran new undersized unit I may have considered it further, but since the subject unit was beyond its expected life, it seemed best to utilize the existing ductwork and add the return with a larger unit. Anyway, I’m sitting in my 70 degree media room and glad I don’t have that old unit to worry about any longer. The much cooler kitchen is also appreciated.

    For those interested, I paid $9,800 (net of rebates but tax and install included) for a York 5 ton split system (upright air handler in a utility closet) with a 12 year warranty and a 3 year service contract from a reputable dealer (locally owned company that’s been around 50+ years). I probably could have saved some money by putting more effort into it. They originally quoted me $13,500 but after some casual discussion they agreed to reduce their price to what they claimed was ther best price. AC companies are tough to negotiate with here this time of year as it is their busiest time of year by a long shot.

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  3. I live in a 5300 sq.ft. one level home. One room, our media room, is where we spend most of our time. We live in Phoenix and on hot days the media room only cools to 78-80 degrees. Currently, it is cooled by a 4 ton central heat pump that also cools the kitchen, dining room, laundry room, a bathroom and the family room. The media room, which has quality insulated duct work and 4 existing 12″x4″ vents and double doors, but no return. I prefer the doors closed for noise control reasons. It is the hottest room in the house, partially because it is on the south east corner of the house with windows on the south and west side, plus three big screens and other AV equipment generates additional heat. We want to be able to get that room to 70 on a 115 degree day. Heating ability is of no concern.

    I am trying to decide whether to purchase a new heat pump and air handler and build in zones, or simply add a smaller split system in the media room which is 620 sq.ft. There is attic space. I lived throug a complete HVAC re-design in my last house (dual 5/1 ton Trains, l20i, with 5 zones) and am tempted to just address this issue with a split system. I would benefit from your thoughts on whether you think this situation is unique enough that a split system makes sense.

    Great forum, thanks in advance.

    Matt

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    • Matt – Thanks for the post and well stated situation. You raise some really good questions so I will try to provide a few suggestions.

      First of all, you have properly identified some unique challenges for removing heat from your media room – southern exposure, south and west facing windows, Phoenix heat, AV equipment heat source, etc. One other important point you made is that there are no return air ducts in that room. When you shut the doors to that room you are probably reducing the cool air delivery to and heat removal from the room significantly. Basically, the air pressure in that room with the door closed will build up and prevent cool air from coming in as fast as it should. There is also no way to remove the heat generated from the windows and the AV equipment since it has nowhere to go. You get reduced cool air coming in plus you are not getting rid of the heat being generated.

      Many people think air conditioning is about simply providing cool air to a space but it is also about “removing the heat” from the space – especially in Arizona where humidity is not the main problem. So, here are a few things you can try to get some of the heat out of that room. I have seen some people cut vents right above the doors to closed bedrooms or high on any wall that leads to another room or hallway that is connected to the air returns. Just put some diffusers on each side like you have on your cool air supplies. One other approach I have seen is to put a “transom “, essentially a little fold out window right above the doors to your room. In the years before AC was common, you used to see these in public buildings to allow heat to exit the rooms into a ventilated hallway.

      Before you do any modifications, I would suggest experimenting by leaving the doors wide open on some hot days to see if you can get the temperature down with only the improved return air flow through the open door. You might also have to augment with a ceiling fan or other well positioned floor fans near the AV equipment. I am assuming you already have thermal shades on the windows but if not, that might also help when the sun is out.

      If none of that works to get the temperature down in that room you might have to talk to an HVAC contractor about getting more cool air to the room and adding a ducted return. While the contractors are there, have them do a load calculation to make sure you have your equipment sized right for your particular application (window, southwestern exposure, AV equipment, etc). You might need to talk to a few different contractors before you get one that really understands your unique situation so be prepared for the time and effort required for these important meetings.

      If the contractors decide your system is simply too small for the unique load conditions in that room and your current central system is pretty new, talking to them about adding a ductless mini-split to that room is probably a reasonable solution. However, I would also have them address the air flow problems while they are there so your new mini-split and central system can work together more effectively.

      If your system is older (e.g. maybe 10-15 years old or more for a heat pump in AZ) or has needed increased repairs recently, you might be looking at total system replacement in a few years anyway. If this is the case, you might want to go ahead and get a new ducted central system, sized properly for your current overall requirements and have them also look into fixing the return air issues in your media room and adding some zones if you want. Some high efficiency systems are available that provide both energy cost savings and improvements in comfort and sound performance so I would ask the contractors talk to you about those options as well as any utility or local rebates that are available for high efficiency equipment.

      In any case, we usually suggest getting at least three quotes from qualified contractors for both ducted and ductless solutions if you are still undecided. I hope these suggestions are helpful.

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  4. I have a 168 ft studio/ playhouse I would like to hear all winter….in Wisconsin. I do not want propane which is the one that usually pops up. I saw these and thought 2 birds, one stone. Would you consider this a viable option?

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    • Amanda – that would work for summer air conditioning and also for heating on days and nights when the temperature is above about 20F. When it gets really cold outside the mini-split unit would probably be running on electric resistance heaters which are expensive and not very energy efficient. Ask a few contractors what they think but you might need another heating source to go with your mini-split A/C heat pump as it gets pretty cold in WI. Hope this helps. Good luck with your HVAC project!

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      • sorry, meant to say “expensive to run”. the backup heaters are internal and usually built in to the mini-split heat pump systems a standard equipment. They just draw a lot of electric power when it is really cold.

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      • Why keep repeating the myth that mini-splits would “probably” run a resistive heater. Modern mini-splits like the popular Fujitsu and Mitsu do not have resistive heaters at all. Their best models use the air source heat pump all the way down to -15F at a reduced capacity, though full capacity can maintained at temperatures above 0F. Now the COP may not be 3:1 at -15F but at temperatures above 0F it would still be well ahead of electric heat.

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        • Hi dm – These are all good points so thanks for sharing. I believe the comments we have received on this topic and the research that was done by the DOE recently (http://info.ornl.gov/sites/publications/Files/Pub34446.pdf ) would support your point that the capacity and efficiency of heat pumps will fall off significantly as the outdoor ambient temperature falls. Heat pumps can be very efficient when they take heat that is available in the outdoor air to move into your home but when it is really cold outside there is just not enough heat energy in the outdoor air to move inside. As you pointed out, this could affect the overall heating capacity of the system during these cold periods and could also affect the discharge air temperature which affects the comfort of the occupants due to cold air drafts.

          Also as you mentioned, some newer premium systems in the market now have the ability to augment this shortfall by over-speeding the compressor to generate higher internal heat of compression at lower ambient conditions. However, while this heat of compression method is more efficient than resistance heating it is still less efficient than a heat pump running at higher ambient and probably less energy efficient than conventional gas furnaces or boilers they might be replacing (depending on the system) and this is the question many of our readers have been asking. The issue you also raised about reduced heating capacity at low ambient conditions is also very relevant in Northern climates. Using less heating capacity when it is really cold outside for extended periods may not be an option if the heat pump is the only heating source in use.

          We will continue to research this topic and should have some new data to share in a few months. Thanks again for your comments and suggestions as we should have been more clear about the over-speed methods used in certain systems.

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  5. Situation:
    Need to replace an older HVAC forced air gas pack now as it is dying. However, planning on a major remodel in the next 18 months. Walls are to be moved and removed. Some rooms combined.

    Question:
    Once installed, how easily is it to change the wall/floor units to a new location in the house? Would that be super expensive?

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    • Hi Wayne – We always recommend getting multiple quotes from different contractors for different types of systems, especially when the job is complicated. It sounds like you need an interim solution and a long term solution once you get your layout established. I would run both these situations by at least three or more good contractors to see what they have to say about it. For example, the cost might depend on how long or complicated it is to run and move the refrigerant and condensate lines and whether they need to be lengthened, etc.

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  6. I am debating between central air and a heat pump mini split. We have a 1400sf home with forced air heat so we have ducts. Right now we cool the house with a window unit in kitchen/family area and a portable unit in bedroom. The HVAC guy says an 18k btu unit installed in kitchen/family area will cool whole house if we use our ceiling fans and/or fan from furnace to circulate the air. The 12k window unit cools most of the house except bedrooms so this seems do-able. The cost difference is $200 less for the split and the mini split has a $1k tax credit making it significantly cheaper than the central ac. I am torn about which way to go. Any suggestions?

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    • Hi Kat – Here are a few thoughts and suggestions. You will probably see improvements with mini-splits over your existing window AC units in the form of energy cost savings and you will also get the benefits of remote control for each unit and you will get your windows back. On the other hand you will also now have some new indoor units hanging on the walls in your living spaces. In general, mini-splits are better systems than window AC units in most ways but they both lack the whole home air flow and filtration you get with a central system. Relying on ceiling fans to move air from one space to another is an option to augment this but it costs money to run those fans too and that cost is not always captured in the literature and energy use calculations.

      If you went with a high efficiency ducted system you could get equal or better whole home efficiency along with whole home air flow and air filtration and you might even qualify for additional utility and government rebates depending on where you live. Other advantages of high efficiency ducted systems could include better humidity control, sound and temperature control benefits. You can also view and search other the posts on this site and this article specifically to hear more about some of the experiences people have had with various systems in hot, humid climates. For example, over-sizing a system for a space (e.g. 18 versus 12) could cool the air in the space well before it has a chance to adequately remove the humidity so you might ask some contractors about that as well if you live in a humid area.

      In conclusion, will you realize benefits from upgrading from your window units to mini-splits? The answer is “probably yes”. Could you realize even more comfort and energy savings and rebates from a ducted central solution? That answer is also “probably yes”. You could also ask contractors to quote a central heat pump system and leave your gas furnace in place to get a “dual fuel” system which could give you the benefits of having both gas and electric heating options and save even more on energy.

      Bottom line – you should get multiple quotes for both approaches (ducted and ductless) from more than a few contractors before you decide and make sure they also quote high efficiency systems with any state and local utility rebates. I know this takes time but this is a big, long term investment. You might also ask a local realtor which solution will be more likely to enhance your home value in the long term.

      It really boils down to what you want out of your HVAC system for both the short term and the long term. Good luck with your HVAC project!

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  7. We have a 1400 sf house in Lubbock, Tx, where our son and roommate live. It has central air and heat, but the bedroom farthest from the unit just does not cool. Humidity is not a problem in Lubbock, but blowing dust is. I have been considering a Mitsubishi ductless system (small unit) to help cool that bedroom. Any suggestions?

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    • Hi Peggie – ducltess mini-splits can usually provide effective spot cooling to reduce some of the “end of the line” problems like you described. You can just use the mini-split in conjuction with your central AC but you should have the contractor calculate the size (capacity) you need before you install it. Here are some other, lower cost options you might want to try as well. If you reduce the air-flow to some of the other vents in your home you might get more airflow to the fartherest bedroom. You might also ask your contractor if your blower motor can be set to run a little faster or you could use fans to get the cool air down to that space. Hope this helps.

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  8. Living in Miami Beach, I struggle with humidity control more than anything else. My home is comfortable and uses three central A/C zones. Never had an issue. My garage, which I converted into a “brewhouse/mancave” was also fine with a wall mounted a/c unit, especially after I sealed up the garage door to eliminate leaks and insulated it and the roof. The wall unit however was very expensive to run so I decided to spend about $1200 on a mini split. I have regretted that decision because the humidity in the garage is often at 60, 70 and even 80%. It’s not RH because the mold issues that have arisen say otherwise, not to mention that one can just feel it. I have to set the temp at 63F AND open the door (not the main door the side door that connects the garage to my house) in order to bring the humidity down to a comfortable 50%. But to get there, I have to have the temp on very low. The manufacturer (Ecox) is ZERO help.

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  10. look like you have walmaunt AC unit :), thats like helicopter.
    Just put in you bedroom Fujitsu 9RLS3. Thats hi ef single zone 33 seer.
    You an see big difference on bill and no any noise. If you like install AC by yourself i give you some advise just sand me email

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