Four Myths About Ductless Mini-Splits

Frank Landwehr
by |
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.

Share
print

Was this helpful?

Vote This Post Up 634Loading...

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

  1. Interesting article. thanks for sharing! I live north of Seattle (edmonds) and I have a ranch/rambler house that is 1500 sqft and has no ducts. We have electric baseboards everywhere and our electric bill is painful in winter over $300 a month but only $50 in summer with celling fans. I have a gas hook up but putting in ducts can cost $4-5000 and a gas furnace and install doubles that so 10k. Do you think a single 24k mini split 2 ton unit would be enough to warm the house cheaply even when it is around 32F outside or would I just end up using the electric baseboard heaters and high electricity bills? Thanks in advance for any insight you can provide!

    Reply ↓

    • Hi John. Here are a few things to consider. From your comment it sounds like energy used for heating is the primary challenge with your situation. Adding a heat pump mini-split unit should improve your cost of operation relative to baseboard electric heaters for the ambient temperatures above about 15-20F (well below your 32F question). Heat pumps work really well when it is cool but not really cold – likely in your area for most of the season. When it is really cold outside, there is not enough energy in the outdoor air to pump into your home and the unit will switch over to auxiliary heat anyway which would be similar efficiency to your baseboard heaters. We usually recommend “adding” units like this to the heaters you already have for at least one or two seasons to make sure you are ok without them and also to use as a backup system. To your question about sizing the system for your space it would be best to have a qualified HVAC contractor do those calculations which account for such things as windows, insulation, air leaks, etc to get the right capacity. One other point we try to make in these situations is that adding a new, higher efficiency system will not reduce your energy bill if you run it more than your old system. If you have a particularly cold winter and you keep the temperature warmer than you did with your old system your actual energy bill might be higher. Better efficiency only yields lower energy costs when you run it in a comparable manner. Also, we recommend getting 2-3 estimates from local contractors before deciding. Good luck with your HVAC project!

      Reply ↓

  2. Does anyone know if there is a mini-split that has a fan that will go off from time to time? Like a regular AC system? We are being driven crazy by the continuous fan noise of the unit we installed.

    We have a unique small house and a mini-split fits our needs here in FL. But noise unbearable. Especially for me as I can hear the high-pitched hum. Sometimes we think the system is defective.

    Reply ↓

  3. We live in Thousand Oaks, California, in a 1,400 square foot house built in 1963 with electric baseboard heat and no ductwork/air conditioning. We only get too hot and/or too cold about 10-20 days per year. Is it worth it to install an air conditioning system? Window units are not an option due to the shape, type, and locations of the windows. We have ceiling fans in all of the rooms. And our portable unit on wheels can’t be used in the bedrooms due to their small size and windows being too high up for the exhaust ductwork, and we’re not that interested in cutting into the stucco/wallboard. Any suggestions?

    Reply ↓

    • Hi Lori – for 10 to 20 days out of the year, in Southern CA you may not want to go deal with the expense and construction issues associated with a whole-home HVAC solution. You could try having a contractor install a small ductless mini-split, heat pump system in one room (probably a bedroom?) that gives you the most discomfort on the extreme days and see how you like it. This system coulod augment your baseboard heat in the winter and give you some cooling in the summer. If you like it you could add more later. You should probalby get a couple quotes from different contractors and make sure the one you choose understands your situation and what you are trying to accomplish so it can be sized properly for your space.These units will use an indoor evaporator that hangs on your interior wall and requires a hole to be made to get the tubing and wires to the outdoor unit so you should ask the contractor how it will look etc – both inside and outside, after it is installed. Hope this helps. Good luck with your project!

      Reply ↓

  4. I respect that the author has done some research, but there are some glaring problems with some of this information. First, ductwork is rarely if ever run inside the conditioned space. Second, all split (ductless or central) systems have at least some of the lineset run outside of the conditioned space, with most having ALL of it run outside the conditioned space. This is more or less a non-issue though since the heating or cooling loss from an insulated refrigerant line is fairly negligible. Third, the costs associated with installation simply cannot be summarized like that. 2 houses with 2k sqft space could have vastly different requirements for a ducted system.

    Reply ↓

    • Hi Amedaius. I totally agree with your suggestion that replacement installation costs (for both ducted and ductless systems) are often difficult to estimate without actually being on the job, doing the load calculations and figuring out clever ways to configure the system(s) in an existing space. This is why we usually suggest getting 2-3 quotes from a few different, qualified contractors before deciding on both the equipment and the contractor doing the installation.

      Also, your points about internal and external ductwork and line sets were addressed somewhat in the DOE study mentioned above. I am not sure about frequency of exposed ductwork within the installed base so we probably need to do some more research on that at some point. Thanks for your comments!

      Reply ↓

  5. There’s a lot of different opinions and hype about these systems and the bottom line is they are very good for what they were designed for, but not necessarily every application. I have seen these is use overseas and thought they were pretty neat long before I ever saw the first ones introduced here the USA. Keep in mind that in Europe there is a lot of urban living (apartments) and smaller homes than here. Much of the older construction there utilized steam radiator heating or electric and no ducted heat or A/C that we commonly see here. A/C was very rare even in Southern Europe (Spain & Italy). These units were ideal adaptations for over there as you could mount the compressor unit to the outside wall even several stories up, and mount the rest the ventilation unit on an inside wall.
    They were never meant to replace your home A/C compressor type unit set up to use the heating ducts in your home. Also great to use in small cabins which is why I’m shopping for one. When I was deployed, our CHU’s in Iraq and A’stan utilized these type units and kept everything heated and cooled quite comfortably. Basically, if you have ducts use them – much more efficient and economical even if you have to replace the compressor unit outside. If you don’t or have smaller spaces to heat/cool, additions, shops, cabins, etc. – it’s not a bad way to go and they work very well. Your choice, I just thought I’d add my two cents…

    Reply ↓

  6. I’m thinking about replacing my 30 year old unit for a mitsubishi ductless system. I”m remodeling my home and I’m moving the unit to a different place in the house and it would be more expensive with a traditional ducted unit. But I live in souther Louisiana and I’m concern with humidity. Can you elaborate more on this issue.

    Reply ↓

    • All AC units dehumidify just due to how they work. The air passes over 40 degree evap coils, which draws out moisture that is above that dewpoint. Now, some newer AC units also have a dehumidistat to control humidity beyond that, but it is pretty unnecessary. Both central and ductless AC will dehumidify, and the condensate will have to be piped somewhere (some systems pipe it directly to the drain line of your house, and some people opt to pipe it into their water collection system for landscaping).

      Reply ↓

    • Hi Arturo – There have been concerns posted by visitors to this site about humidity control and these seem to be mostly related to the use of multiple units or units with multiple indoor evaporators, being applied in fairly large spaces. This may be related to managing airflow among the various “zones” assigned to the evaporators as documented in a recent DOE study – link below.
      http://info.ornl.gov/sites/publications/Files/Pub34446.pdf
      In highly humid areas, the energy required to remove humidity can often be greater than that required to maintain temperatures and the key to removing humidity is to insure there is adequate airflow across the cold coil for long periods of time. As an air conditioner runs, the moist air hits the cold indoor coil, condenses on the coil and drips into a drain pan and is then piped outside of the conditioned space. If something happens that reduces the amount of air moving across the coil(s) then you might not have enough humidity removal. For example, if the system is oversized (too many tons, or BTU/Hr) for your space then it may not have enough run time to remove all the humidity. If your mini-split zones are too far apart and there is not good airflow sharing among the units you might also experience humidity spikes in some areas (zones) or at the interface of these zones. Another problem that visitors have posted deals with the moisture (condensate) removal. Each indoor unit (evaporator) will have a tube that drains the moisture outside the space. If these become clogged, the moisture will drip down, out of the bottom of the indoor evaporator and into your living space and the amount of water that will drip out can be significant at times. You could have the same drainage problem with a ducted system but these usually only have one drain and are often in the basement. If you go with mini-splits make sure you ask your contractor about how to maintain these drain lines.
      On this site, we usually recommend getting 2-3 estimates for both ducted and ductless options, from different contractors in your area before deciding. Moving the indoor or outdoor unit or having them relocated in a new area may not be as expensive as you are thinking but you will not know until you get a few different quotes. Some contractors are better at this than others so it makes sense to get a few different opinions.

      Reply ↓

  7. When they come out with a fan/coil unit that sits near the floor, under a window for example instead of up near the ceiling, acceptance will grow. The units hanging on the wall near the ceiling have a retrofit look.

    Reply ↓

    • Hi Ron – Thanks for your post. One other recent post indicated that the reason they like to place those units high on a wall or in a ceiling is so the cold, supply air falls and the warn air in the room rises to cool the whole room. I guess that is what you were suggesting but I was not sure.

      Reply ↓

  8. I have a cement block house that was built in 1956. It has a minimum amount of wall insulation that I can’t do much about and windows that I am in the process of replacing as I can afford it. My biggest problem is that I have radiant ceiling heat that only works in spots. I can’t afford any more 700+ dollar winter electric bills and 300+ summer bills. I’ve had the contractors out for estimates and have settled on the one I want to do the work. My question is the estimate between a variable speed heat pump with a variable speed air handler with rigid fiberglass duct system and all the other standard equipment and the estimate for a mini split system capable of do the same job is within 100 dollars of each other. They each have pros and cons for my needs and because of the reading and research I have done I am leaning towards the mini split. What I’m wondering is which system in anyone’s opinion will reduce my electric costs and heat and cool this thing I call home. I am disabled so lowering my astronomical electric bill is very important to me. Just so you know my house is only 1000+/- sq. ft. thanks for any opinions anyone can give me, Randy.

    Reply ↓

    • Hi Randy – From your post I can tell that you must live in a climate that has full heating and cooling seasons and thus might also have periods of high humidity. Electric radiant heat is usually not very efficient or cost effective so you should realize some savings from going away from that as your primary heating source. It is not clear what air conditioning system you have now but if you have window/room AC you should also realize some improvement in both energy efficiency and comfort with either ducted or ductless systems.

      One thing you might want to consider is how much capacity you have for both heating and cooling now versus what you are going to have when you install your new system. Some people install a higher efficiency system but still see an increase in energy use because they had to increase the capacity level of the new equipment (measured in BTU/Hr, Tons, etc) to match the needs. It is important to have a good contractor do the calculations to estimate what your new energy costs are going to be with various system options and sizes. The system needs to be sized right or you may not achieve good performance on extreme days and good humidity and temperature control on moderate days and most nights. Again, you might get better, more efficient cooling than your room units but if you add BTU’s you could be using more energy even though it is a more efficient system. We have seen people post about this on our site so it is probably worth considering.

      On the mini-split option, if your layout allows you to separate your home into “zones” and you can get enough indoor evaporator heads into those spaces you might be able to better manage the energy spent on conditioning those spaces (i.e. turn them off or down when not in use). You can do the same thing with a ducted system with variable capacity but you have to have the contractor set up the ductwork to do that. You might want to ask your contractor about maintaining proper air flow and filtration to various parts of the house as well. You should also try to get either the ductwork or the refrigerant lines into the conditioned space. Even though these are usually insulated, you might see energy lost if they have a lot of areas that are exposed to the outside. A comparison of ducted versus ducted systems was done by the Department of Energy a while ago so you might want to review those results before deciding.

      http://info.ornl.gov/sites/publications/Files/Pub34446.pdf

      It also appears from your post that you are going to use a heat pump in either the mini-split or ducted format. If so, you should note that heat pumps work very efficiently until the outdoor temperature goes below a certain level (usually about 15F). Once it gets below that temperature, your heat pump will usually go to an auxiliary heating mode which involves built in resistance heaters – and thus, will be less efficient. If you live in a climate where temperature frequently gets that low for long periods, you should ask your contractor about this. Some variable speed systems have extended the operating range to below 15F outdoor ambient but not all so you probably need to ask. For ducted systems, some people also use both a gas furnace and a heat pump to achieve high efficiency across a wider range of outdoor ambient conditions and also give some flexibility to deal with the relative costs of electricity versus gas throughout the heating season. These are called “dual fuel” systems.

      The efficiency ratings for ducted systems and mini-splits are pretty much the same. SEER (Seasonal Energy Efficiency Ration) is the rating for cooling and HSPF (Heating Seasonal Performance Factor) is used for heat pump heating. If the ratings on various systems are the same and the systems are about the same size (see above) you should expect similar energy costs with either one – depending on how much you use them. Again, your contractor should be able to estimate this when the sizing calculations are done.

      You mentioned that you are planning to improve your windows in the future. You should discuss this and any other improvements (insulation, etc) and other layout changes you are planning with your contractor because these could affect the overall capacity needs for your space. With a variable capacity system it could adapt to these changes but it might still be important to discuss. There are also some high efficiency “stepped” capacity systems that might provide a lower price point option versus the fully variable system so it might be good to ask about these as well.

      I hope you find this information helpful. Good luck with your HVAC project!

      Reply ↓

  9. Thanks for creating this forum – it has been a very interesting read as I research how to address my HVAC situation…

    I own a 2,400 sq ft home in NJ built in 1970 that has central air with ductwork to all rooms. Unfortunately, the system in place does a terrible job cooling the upstairs, with temperatures about 10-15 degrees warmer than downstairs. To address this issue, we run window units at night in the 2 currently occupied bedrooms and turn up the central at night in the summer. To make matters more complicated, the upstairs bedrooms at the end of the house furthest from the furnace do not get sufficient heating in the winter, so my daughter’s room had a space heater last winter to keep her warm.

    We are expecting baby #2 in November, so we are debating how to address this situation in both bedrooms for the kids. Originally, I was considering electric baseboard in the kid’s rooms and using window units in the 3 bedrooms in the summer to supplement the less than efficient central air unit. My concerns with this solution are both efficiency as well as exposing a baby and toddler to hot baseboard units. Would a 3 unit (master and 2 bedrooms) ductless mini split system for my upstairs seem appropriate here? It would address my heating and cooling issues in one step, increase the efficiency of my current alternative, and be a safer solution for young kids. How does this compare to the upfront cost and efficiency cost of adding a second zone to my existing central for the ability to heat/cool the upstairs and downstairs separately?

    Thanks!
    Gary

    Reply ↓

    • Hi Gary. Thanks for the post. Here are a few things to consider. If you read through some of the comments to this article you probably have concluded that we recommend getting at least 3 quotes/estimates from various contractors, and to do this for both ducted and ductless solutions. Some contractors can quote both system types by the way but you might need to ask them. Each contractor might have a different approach to solving your HVAC problem so it could help you to get some different ones to look at it.
      When you have contractors over you should have them do some measurements and calculations to determine what size system you need for your whole home and also the spaces that are not being conditioned properly. Most contractors know how to do this. We support the industry group ACCA and they have a contractor locator tool. Here is the link.
      https://www.acca.org/locator

      In any case it might be good to consider the age of your system before making this decision. Most systems are replaced when they are about 16 years old (national average) so if you have an older system you might not want to do an “add on” solution and then turn around and have to replace your main system if it quits working in a few years. The point is, you might be able to address all your problems with a partial or full replacement of your existing system along with some modifications to your existing ductwork to address the hot/cold spots on your second floor. However, if your existing system is not that old, then you could consider adding a second system – either central or ductless.
      A ductless, add-on system would have refrigerant lines running from the outdoor unit to each of the indoor cooling units located on the walls in each bedroom. You might be better off quoting individual, mini-split units for each bedroom and avoid all the refrigerant lines. On the other hand, if you decide to add a central, ducted, heat pump system to your second floor, you could place the air handler and ductwork in the attic (if there is room up there) and run new, additional distribution vents to each bedroom. Either approach might address both your heating and cooling needs and also give you a 2-zone set up – which is good for temperature control and energy savings. However, if you end up replacing your old system with one, new system, you might consider a 2-step, 16 SEER, high efficiency system. Having 2 steps of capacity might also help you address some of the cold/hot spots on extreme days but make sure the contractors perform the calculations to help you select the right system size.

      On the topic of energy savings, since you are “adding” a new system you could also be “adding” to your energy bill depending on how much you run it. The new systems will probably be more efficient than your old system but if you have to run both the old and the new systems to keep up, you will probably be using more energy unless you can significantly reduce the runtime on your existing system. If you replace your old system with a new, high efficiency, two –step system you might be able to reduce your overall energy bill. The contractors quoting new systems should be able to estimate this and also advise you about any local rebates available in your area.

      I would like to make one other point about both ductless and ducted add-on systems for your second floor bedrooms. In either case you will be getting a new source for AC in the summer. However, to get additional heating in the winter you will need to get a heat pump model. Heat pumps are sort of like AC units that can run in reverse in the winter to move heat from the outdoor air and into your space. The problem with these systems is that they are not very efficient at very low temperatures (e.g. below 15F). However, since you might be keeping your existing furnace, the combination of that heat source with the auxiliary heaters built into the heat pump should help you keep up on the colder days and nights. These heat pumps would also not have the exposed resistance heaters you mentioned.

      Again, take the time to get a few different estimates from good contractors for both ducted and ductless. Good luck with your HVAC project and thanks for posting on our site!

      Reply ↓

    • Hi Julia. On this site, we recommend getting at least 3 estimates from qulaified contractors for both ducted and ductless options before deciding. Prices and installation costs ofen vary greatly for various reasons. Also, make sure the contractor does some measurements and inspections to make sure the equipment is the proper size for your space. Good luck with your HVAC project!

      Reply ↓

Let us know your thoughts

Your email address will not be published. Required fields are marked *