Busting Myths on Ductless Mini-Splits: Part II

Revisit the Four Myths that I Proposed were “Busted” Three Years Ago

Revisiting the July, 2013 post, “Busting Four Myths About Ductless Mini-Splits”

When I wrote the “Busting Mini-Split Myths” article in 2013, I did not think it would become the most viewed article on our new website but it has over 365,000 page views and counting! I guess I would attribute the popularity of this topic to how new these systems are and how different they are from conventional, ducted, central HVAC systems, which are found in over 80% of the homes in the U.S. However, in addition to the volume of traffic the number and quality of the posted comments and questions has also been remarkable (over 270 to date).

Although we started out trying to provide a balanced view on this new technology for consideration, I found that I also learned some things as the user feedback continued to come in. This led our team to do some additional consumer research into the U.S. Mini-Split phenomena and this research will now appear in some new articles written by Eric Strausbaugh.  Without going into the details of the study, I thought I would use some of the findings from the study, along with the knowledge contained in the many posts on this site, to revisit the four myths that I proposed were “busted” three years ago.


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

Status: Still Busted. While mini-splits are growing a little faster than the sales of central systems on a unit basis, the dollars spent on these systems and the number of BTUs of capacity getting installed is still a fraction of that spent on traditional central systems. The reason for this is that the majority of the installed base of homes (over 80%) have pre-existing ductwork. It is simply less expensive to replace a ducted system with another ducted. The air quality and humidity control benefits from central AC are also contributing factors to the staying power of central systems.

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

Status: Still Busted. Our recent research suggests that only a small percentage of people are trying to use mini-splits as a whole-home heating and air conditioning solution; these are mostly in very small homes with no existing ductwork available. What appears to be more popular recently is the “hybrid” approach of keeping the central system for the bulk of the whole home comfort, air flow, air quality and humidity control but also use one or more mini-splits to address areas where consumers want more direct control or where the central, ducted system is not keeping up. Our research articles will go into more detail about this and theories about why this is happening.

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

Status: Mixed. Based on our research and the comments on the original article, I would say that there are definitely instances where poor or failing ductwork has led to major problems with central systems. No one can argue that the most efficient way to run an air conditioner is to turn it off. If you intend to turn off an entire mini-split zone for long periods, these systems will use less energy than a home that does not have zones that can be shut off. I am giving this a “mixed” rating due to the comments about people also using zones in ducted systems, in addition to comments about energy losses in the long line sets for mini-splits.

However, it has been shown that mini-split installation can also have serious “leaks” as long line sets on the outside of the house can pick up heat in the summer and lose heat in the winter. The result can be significantly higher energy costs than would be expected based upon the rated efficiency of the system.

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

Status: Mixed. Based on user feedback, I would have to say that for certain situations mini-splits can do a great job and at reasonable costs. However, it would also appear that for whole-home solutions in larger, U.S.-style homes, the hybrid approach of using a base central HVAC system along with some mini-splits for certain areas provides the best overall approach to both comfort and energy efficiency. Combining this hybrid approach with an automated duct zoning system for the main central HVAC would also improve the performance of the overall hybrid approach.

The Bottom Line on Ductless Mini-Splits

If you want to learn more about this topic, check out our first article on the survey of over 350 people who have purchased mini-splits in the past 1-5 years. In the meantime, we would encourage anyone in the market to get a few different quotes for each of the various system types that are available today and consider mixing and matching them to meet your unique needs. It is important to get multiple quotes not only to get the best price, but also to find the right contractor who can recommend the best equipment solutions for your situation, then install and service them well.

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96 thoughts on “Busting Myths on Ductless Mini-Splits: Part II

  1. A mix of both techs exist that would work great. You can hang a small air handler to keep duct runs short so 1 unit can for instance do both the master bedroom and bathroom. Thats just 1 example. Typically these can be installed in the conditioned space keeping losses down.

  2. Mini splits can be a good solution for some areas, but they can introduce some of the same problems as central heating and cooling, and a real need for regular maintenance by a licensed contractor.

    Even with a dehumidifier and air filters running in the same room with the mini split in a very clean home, the problems with mold and dust can be intractable.

    It is a flexible alternative to standard central air, but should not be viewed as something that can be safely maintained without regular servicing by skilled technicians.

    Mini splits are nowhere near as good for air quality and home maintenance as plain old fashioned radiators and plain old window a/c.

    I would say don’t get a mini split unless you have a budget for dehumidifiers and hepa filters and professional maintenance.

  3. Hi, so I wanted to jump in on this conversation as a contractor who has and continues to install both traditional AC/Gas, Heat Pump, as well as mini and Multi Split Heat Pump systems. I’m in south Texas BTW.

    Several of the facts above may not be necessarily false, but they are at the very least extremely outdated and don’t offer a fair comparison between systems.

    1. Price – a basic 14 seer or 16 seer single stage AC/Gas System will ALWAYS cost far less than a quality Mini Split application for a whole home.
    However, this is not a fair comparison of efficiencies and price. A typical whole home install with a multi zone mini split will run in the range of 19-24-ish or higher SEER. Now we can get reeeealy down in the dirt and start mixing ducted and ductless, but the bottom line here is that when compared to a traditional AC/Gas or even HP system at 19-21 SEER rating, the multi zone multi split will cost about the same.

    2. Comfort – there is no question here. These systems are not designed to save you money up front. They’re designed to provide comfort. In our climate these systems operate very efficiently, providing heating capacities of 100% down to 17-20 F. Mitsubishi has a HyperHeat system that will provide 100% heating capacity down to -5, but for our climate, a standard HP works just fine. It’s worth noting that a conventional Heat Pump will tap out and not be worth running at much below 40F.
    But where does the comfort come in? Well, if I want to keep my living space at 76, my bedroom at night at 70, and my kids rooms at 74, I can do this with a multi zone system.
    This setup will also eventually (fairly quickly) lay for the added initial cost because I can set back my living areas to 78-80 over night and bedrooms to 78-80 in the evenings when they’re not in use. So less use = less electricity.

    3. Loses due to leakages. A conventional ducted system that is installed properly DOES NOT leak.
    Coincidentally, neither does a properly installed and insulated line set. It’s all determined by the installation folks. It truly has nothing to do with the type or manufacturer of your ducted or ductless mini, multi or conventional system.

    4. Zoning – this is one that can probably get me in trouble, but please, PLEASE for the love of God, stop believing in air zoned systems like they’re the answer to all our comfort and energy ails.
    Zoned air systems work in certain conditions, and when designed properly. It has been my unfortunate experience as a building scientist and a contractor that this is not the case a vast majority of the time.
    Any zone that is smaller than the minimum capacity of the condenser/indoor blower will do nothing but waste energy, and in humid climates contribute to high humidity and possible mould in the space. Physics of this are simple, you can’t fit 10lbs of doo doo in a 5lb bag.
    You either have to use a bypass damper, which will reduce the capacity of the unit, or you have to have a “dump zone” which pretty much defeats the purpose of the whole system. So while useful in certain applications, it can NEVER beat the true zoning capabilities of a quality Multi Split.

    5. Humidity – this one is simple. Before you decide on a system, look at the engineering data for that specific unit. You will find that mini/multi splits remove far more humidity when properly sized than a conventional system. This is for us folks in wet climates. Again, key phrase here is “properly sized”. A “by room” Manual J is an absolute must for ANY type of system.
    Also, it’s worth noting that not all conventional nor all Mini/Multi split systems are designed equally. For example, when rating 3 of the top lines in the US (Mitsubishi, Daikin, and LG), the Mitsubishi system can remove up to 3x the amount of moisture than their competitors. Fair disclosure here, I have been a registered Mitsubishi Diamond Contractor for the last 6 years as I have tried the other brands and found the Mitsubishi brand to offer best quality, performance, and support, and thus the best value to my customers who choose to go the Mini/Multi Split route. But still, facts are facts.

    I can probably go on for several more hours, but my main points are:

    1. When it comes to price, compare apples to apples. These systems are not the right fit for every application, but they are an EXCELLENT fit for whole home applications in many situations.
    Example: I did a single stage 16 seer conventional AC/Gas replacement for a home that was 2 stories and had a single 5 ton system on it. Homeowner complained of not being able to maintain even temps between floors. The conventional solution they chose was to go with TWO systems in this case, one for each floor.
    Cost of install – $17,000 total including electrical modification.
    About 3 months later, a homeowner just across town, had the same problem, and after offering them choices they picked a Mitsubishi 5 ton condenser, with two Ducted air handlers connected to the existing ductwork in the home. Each air handler was controlled by its own thermostat, and they both ran off a single condenser.
    Total cost of install – $15,000
    Best part – the customer contacted me almost a full year later to let me know that they hadn’t used more than 950 kW of power any single month during the hot summer. Their old energy bill averaged 1,700-2,100 kW per month during the summer.

    2. Do your research and don’t pick a brand of equipment, pick a well trained and reputable contractor who is willing to educate and will give you options. There is no “one size fits all” when it comes to AC.
    And remember, this is the biggest investment in your home other than the home itself. Do you really want to cheap out here? Good work a’int cheap, and cheap work ain’t good.


  4. I live in an attached row house with no attic or crawl space and a flat roof. I am tired of replacing window units every few years as they seem to be so poorly manufactured these days. The heating feature would only be used to supplement the boiler/radiators. Is there any value to switching to a split system as I can’t install real HVAC?

    • It could be feasible, however, we would advise that you have a few licensed contractors perform a load analysis and obtain quotes for the different options available. The ACCA – which is a national contractor organization, has a contractor locator tool which may also help you find a qualified contractor in your area. Here’s the link: http://www.acca.org/locator

  5. Comments from a non-HVAC guy, but a very finicky and experienced end-user POV. I have lived in Japan half-time for nearly 50 years and am *very* familiar with mini-splits, that has been the heating norm for a long long time here. My region, Kyoto, is sort of Washington DC-like in terms of climate– hot, muggy summers and 35-50 daytime temps most of the winter months, some snow but never lasts more than a day. OTOH, my home in the US is in central Massachusetts, w/ real cold and real snow. Bottom line: 50-degrees in Kyoto w/ mini-splits seems vastly colder than 20 degrees in Massachusetts w/ a gas forced hot-air furnace. I am sitting in my Kyoto study just now w/ the mini-split cranking, long-johns, heated socks, “Heat Tech” thermals, down vest, and a hat 🙁 A few observations, mostly related to heating (if you only need a/c, why bother w/ a mini-split in the first place?): 1) for heating, having a unit that is mounted at the top of the wall is not so efficient– heat rises, right? In our very modern high-ceilinged condo this necessitated a pricey angled ceiling fan installation; 2) Even in a large room with the current state-of-the-art mini-split systems (dual body-sensors that follow two persons’ individual movements around the room and adjust fan/temp/etc. according to individual preferences about temp and air flow, “ across ceiling and down” features, etc. etc.)– even then the heat or a/c tends to be blowing right in your face, and this is virtually impossible to avoid in a small room; 3) Ductless? Yeah, well, how about the wall-mounting, the 3″ or better through-wall “irrigation” hole for power, condensation, etc. and hookup to the outside unit? And the outside units are bulky and hard to hide, mount on the wall or cover w/ decorative grating or other stuff, whatever. Some very gorgeous ancient Japanese homes are aesthetically destroyed b/c of this. Also, as pointed out, probably about 3x the cost of a single ducted furnace & central a/c unit, w/ but a single outdoor unit. 4) Remember, you need one for each room–this is pricey and adds to the clutter both in and out of the home. Here in Japan we tend to keep room doors closed to keep the heat in, which means hallways, toilets, and other smaller spaces have neither heat nor ac/c– we use little “body sensor” electric space heaters in toilets and other similar spaces, and simply freeze on the midnight/early AM trek to the toilet. 5) In Japan the price difference between electricity and gas for heating is not so big, but in the US nobody would choose electric over gas for heat if they could avoid it; 6) again– price. I just spent app. $10,000 for a new Goodman 100,000 BTU, Bluetooth, ECM, etc. etc. 96% AFUE furnace w/ add-on bypass humidifier, high-end UV, etc. filtration system, and central A/C–installed, plus I received a $1,000 rebate from our Mass Saves program– for my 2600 s.f., 130 year-old kinda leaky Victorian wood-frame home. And all is very toasty warm! Two years ago I spend $8500 on 4 mini-splits for my 1300 s.f. Japanese condo, not including installation. When I did the renovation I added several gas cocks for natural gas, and I am now thinking of adding a gas heater, a bit to compare costs but also to avoid the down-draft nature of mini-splits. After decades of experience w/ mini-splits, IF I COULD: central ducted heating and a/c *in a heartbeat*!! I repeat this often to my mini-split enamored friends, and hope they get it. OK, enough rant and rave, just my two-cents worth–well, a bit longer than two-cents. . .

    • After reading several of the posts about mini-splits from you folks, here are my two cents…
      Mini splits should not be used as a “primary” source of heating. As several people mentioned in the comments, the indoor unit is not designed to distribute the heat evenly throughout the room / space you might be looking to heat.
      From my experience, central air systems (which I’ve had in my first house), distributes the heat more evenly and faster than the mini-splits, but once the system shuts down… the “chill” comes back immediately (Damn!!).
      Radiators and base-board systems take a while to heat up (Damn!!).
      Throughout my years of being alive and researching the best options to heat myself and my loved ones, this is what I’ve learned:
      Do not rely on only (1) source of heating for your home.
      “If” for whatever reason the system fails, you are “screwed” (excuse the french).

      The best way, in my opinion, is to have 2 sources of heat in the event that “one system” shoud crash.
      My personal favorite is radiant heating below the floor, either electric or hydronic.
      Heat rises (I think most of us learned that before we learned how to write our names), thus making perfect sense that the heating sourse should be installed “low” to the ground allowing the air to be conditioned (heated) as it travels upwards towards the ceiling.
      Not only will the floors be warm while you walk across the floor bare feet, the air in the room plus all furniture will have a constant temperature.

      For those who have a fireplace will understand the following: Ever get the chills and decided to sit infront of the fireplace to warm up… your face and upper body warming up very quickly yet your toes were still frozen? Not exactly my idea of comfort…

      Getting back to the subject, in terms of cost, radiant heating prices have come down significantly over the last decade with manufacturing improvements on quality as well as reliability of these systems.
      10 years ago, the average price for electric radiant systems were anywhere between $10 to $15 per square foot. Now-a-days, the price is about $2 to 5 per square foot.
      I’m in process of building my retirement house in North Jersey from the ground up… for heat I’ll be combining electric radiant for every room in the house as the primary heat-source plus adding a few mini splits for back-up.
      Yes, it’s all electric… that’s why I’m throwing a dozen solar panels on the roof to help keep the electric bill in check.

      Each person’s requirements will be different.
      For some radiant makes sense… like myself.
      For others, a furnace makes sense.

      There’s no right or wrong, just what best for you.
      Remove those shutters and keep your options open.
      Times have changed, improvements in technology happen so fast we can’t keep up.
      Research, learn and do more research before deciding.
      Besides, I find learning about ways to save myself money much better than the wasting my time following on the mess we have in the White House.

      BTW, I’m a commercial and residential builder with a degree in Architecture and 30 years in the business.

      • My House is all electric baseboard. I have a wall gas furnace in the basement for back up as there is no ductwork. For savings I have off peak with power company so electric bill is lower but I do remain without heat for many hours throughout day. I’m thinking a mini split for heat in living room might be more cost efficient than running electric heaters . Thoughts? A.C. would be nice but live in a climate where only would need 2 weeks out of year.

  6. I have a 2 story row house in Philadelphia with radiator heat. It is about 1,500 square feet. Obviously, there are no ducts, skylight in the 2 full baths on the 2nd floor. The house has a flat roof. There is some insulation in the crawl-space “attic” which I was thinking of having double insulated. I really want to have Central Air. I am a 75 yr. old single woman who is working full-time and would like to make these upgrades while I am still working. What would you advise? Thank you so much.

    • We recommend contacting a local licensed heating and cooling contractor to get recommendations on the best equipment options for your specific situation.

    • There is a cost-savings potential to be realized by setting your thermostat setpoint back a couple degrees when you’re not there. But be careful to not set it back too far with a heat pump as it may trigger the auxiliary heat to make up a large setback.

  7. The argument about heat losses in the refrigerant lines is not really relevant, while it’s true that the refrigerant can change temperature several degrees, the actual thermal energy gain/loss is nearly insignificant because the liquid refrigerant does not cool the room, the energy absorbed in cooling the room comes from the phase change of the refrigerant (from liquid to gas) – this is enormous compared to the energy required to heat or cool the liquid refrigerant a few degreees.

    The only place it comes into play is at the points in the cycle immediately following the phase change, for example at the compressor outlet very high temps will be generated and at the evaporator a lot of energy will be absorbed. It’s crucial to have airflow at these points to provide heat exchange, but if the refrigerant has to travel 50 feet through an attic, it’s not really going to make a big difference in terms of cost or efficiency, regardless of whether the liquid temperature increases.

    • Almost mini splits have their expansion devices located in the outdoor unit, so the phase change is occuring throughout the entire line length. If properly insulated it really isn’t much loss, but it is definitely more lineset loss than a traditional system with the expansion device at the evaporator.

  8. I had an hvac pro come in my condo unit to look at my nonworking central ac unit which is split between the furnace. He quickly advised that having the old unit repaired would prove to be more costly down the road as the unit is nearing the end of its life. This could be true but I honestly would love the idea of converting to a ductless mini split system. I asked him about it but he advised that because its a condo, that its likely the association will restrict having that installed because holes will need to be drilled on the outside of the condo unit in order to successfully install the new unit. Before I go ahead and ask the association, I would like some insight on this dilemma I may encounter. Would someone knowledgeable on the topic please offer some sound advice? Thank you in advance all 🙂

    • Gloria, you had an a/c professional advise you, giving you “professional” advice, and you’re now asking for opinions from the masses- most of who will probably not be hvac pros? What’s wrong? did you not like what the professional told you? Hoping for someone to tell you what you want to hear?

      The only uncertainty I see is whether your HOA will allow for it. Your pro raised a real possibility.

      Also, if you’re ever going to sell the condo, I’m guessing most potential buyers won’t be impressed with the split system.

      The U.S. military used them extensively in their living quarters and offices in Iraq, Kuwait, and Afghanistan; probably because that was about the only thing/most viable option available. They are relatively quick and easy to setup and not too difficult to replace when necessary. The various structures that utilized these for heating/cooling had most often poor insulation, if any at all, so that might have been part of the problem, but I was never impressed with their ability to sufficiently heat during the winter. One would think the info from the article about the high cost of air conditioning from the split system vs. the traditional central hvac would have deterred a reasonable person. Sounds like your mind is already made up.

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