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Community and Q&A

Cold weather performance reports from minisplit owners

Martin Holladay | Posted in General Questions on

This morning I drove to town for a dentist appointment, and the digital outdoor thermometer on my Subaru bottomed out at -28°F as I drove through Lyndonville, Vermont.

During the past week, the thermometer at our house hasn’t risen about 0°F, even during the afternoon hours. Of course, all of northern New England and the upper Midwest has been experiencing similar temperatures this past week.

So I’m taking this opportunity to ask owners of minisplits to report on how well their systems are working during the recent cold snap.

Who is toasty? Who is a little cold? If you’ve had problems, how low did the temperature drop before you noticed problems with your ductless minisplit or ducted minisplit?

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  1. user-6947576 | | #1

    The temperature was hovering around 0° F this morning in Western Kentucky and my house was a little cool but not bad. I have a 4:1 Mitsubishi system, not Hyper heat, and it was blowing warm air this morning. My house is a brick ranch with 2x4 walls and fiberglass bats that was built in the mid 1960's that isn't super sealed up, so I thought it was doing ok today. Allen

  2. JeremyArch | | #2

    Hey Martin,

    Happy New Year to you and all the readers out there!

    This is the first winter with my splits. I was a little worried before this cold snap hit and assumed I would be back to pumping wood into my wood stove and some electric baseboard heat for my bedrooms. I was pleasantly surprised that i did not have to fall back on old heating methods. I was able to just let the mini splits do the work. Obviously they were running more but they had no problem keeping the house warm. Set temp on the remotes are at 70, the areas where the heads are stay right on point and areas on the other side of the house and certain bedrooms drop to about 67F.
    I live on the north shore of the St Lawerence, we had slightly warmer temps then you are reporting in Vermont. Daytime temperatures around the 0F night times regularly around -16F with the windchill hitting -31F.
    Its great to know the minisplits can keep up to the cold and I am no longer tied to a wood stove or face ridiculous electrical bills!. I hope everyone else had similar results!


  3. Chris_King | | #3

    Got me a Fujitsu ceiling cassette 1.5 ton to do about 1400 sq ft of heating that is right at the beginning of the walkway. Here in NJ the minisplit had no issues until we hit the teens consistently the house is 2x4 with the rooms furthest away from the unit have roxul installed and walls sealed from the inside. Attic has about R60 worth in it. My biggest issue I think is self inflicted. I removed all the insulation from the crawlspace with a plan to redo it in the fall. Life got in the way and there’s nothing there now. Floors are constantly pinging about 55 on the laser thermometer so I’m pretty sure once I fix that the unit will hum along no problem like it always does. 20s and above the single unit has zero issue keeping up. Once I get the crawl and exterior foam it’ll be fantastic.

  4. GBA Editor
    Martin Holladay | | #4

    That's a great report. Good news to hear.

  5. STEPHEN SHEEHY | | #5

    In our Zone 6 pretty good house, we have two Fujitsu minisplits, 9 RLS3H and 12RLS3H. They've had no trouble keeping up with the cold. Since Christmas, nights have been around -12° F with daytime highs as warm as +10°. We're enjoying a mini heat wave now, at +12°. House has stayed at 70° throughout this cold snap.

  6. Expert Member
    Dana Dorsett | | #6

    A co-worker's three Mitsubishi FH-series mini-split solution in a 1920s bungalow in suburban Boston (Arlington) don't quite keep up with the load at sub-zero temps. I suspect his real problem is the offset between the sensed and actual room temperature, but he has his pre-existing oil-fired steam boiler, and he sets it's T-stat to 65F to backstop the splits. For now he seems disinterested in getting a wall thermostat for the FH12 in that zone, though he sometimes talks about inventing his own operated via the remote-control link, but with control board of his design (enginerds- gotta love 'em! :-) )

    The space where the boiler's T-stat is located is covered by a FH12 zone that may be marginally-sized for the load at 0F (his 99% outside design temp is something like +9F), but it'a adjacent to a kitchen zone heated/cooled with a ridiculously oversized (for the space) FH9. There's more than enough TOTAL ductless capacity in the house to cover it with the interior doors left open, so it's most likely a matter of dealing with the greater temperature offsets at low/very-low outdoor temps.

    It took me 2 years of gentle prodding before he had the epiphany that maybe insulating the foundation walls might be a good idea (it's almost 1/3 of his total heat load right now). He had that project quoted recently, but hasn't pulled the trigger on that yet. So with more prodding maybe he'll eventually buy a Mitsubishi T-stat for that zone, or maybe after he insulates the basement the first offset between the air temp at the boiler's T-stat in the hall the incoming air at the FH12 head near the ceiling on the far side of the living room from an open archway to the hall.

    But in today's lunchtime conversation he was trending toward inventing an even more complicated version of his own, that also controlled the boiler, to make the transition to boiler heat based on when it was most economic, given that his electricity is north of 20 cents/kwh and the COP is going to be at best 2 when running full-out at 0F outdoors. One of the other guys pointed out that it was less than 1% of the time that the boiler would even be needed, and maybe he'd be better of spending his time doing something else, but he isn't easily distracted... By next winter he'll have an insulated and better-air-sealed basement, and maybe this will all go away without adding a wall thermostat to the main first floor zone. (The place does just fine at +15F without tweaks for temperature offsets.)

  7. kcfink | | #7

    Hey Martin,

    Our Fujitsu Halcyon heat pump is keeping up fine until about -10, after which it starts to run a degree or two behind the set point in our Vermont pretty good house. It seems to catch up fairly early in the day once things get back into the low single digits below. I was pleased to find it still pushing out heat this morning at -24, and within 3 degrees of . Our system is a little undersized for the space too (we tend to rely on the woodstove anyways), so if we had a little more capacity I suspect it would pretty much keep up on its own. We have run the woodstove some on these really cold days, so if we had several in a row where the high was below zero it might have issues without supplemental heat, but I don't think we would freeze.

  8. GBA Editor
    Martin Holladay | | #8

    Thanks for all the reports. Keep them coming!

  9. ohioandy | | #9

    Here in NW Ohio, we're spending what seems like a lot more than 1% of our time below our 99% design temp, which I think is 5. Our lowest has been only -11 so far; feels like deep south compared to some of you. My two Fujitsu 9K units are having no trouble, although at these temps they're often a couple degrees below the setpoint (no problem, just raise the setpoint and accept the factory algorithms.) The ceiling cassette on the 600 sq.ft. main floor is doing most of the heavy lifting, and the upstairs mini-ducted jumps in once in a while. I've got each one a separate outdoor unit, so if one fails I've got redundancy. (If the electricity goes out, I got nuttin, except for what I expect is several days of coasting in my tight house before things get unworkable. We've had no power outage in four years.)

    I think back to my 2013 battle with local HVAC places, trying to find ANYONE who would supply minisplits based on my Manual J, which showed a conservative heating load of 16K. The local Mitsubishi dealer refused to install 18K total, even if I signed off his usual warranty. They wouldn't go under 48K, saying even then I'd "probably complain." Eventually found a libertarian Fujitsu outfit that ordered me exactly what I asked for, allowed me to install it, and charged only for the tech to come out and do the lineset hookup and startup.

  10. mikeferro | | #10

    My pretty good house in Maine has a 9k and 12k Mitsubishi hyper-heat mini-split. The design heat load for the house is 12k, so I have some extra capacity. That said, I have seen low temps of -14 and high temps of 0 outside the past several days. Inside, with a set temp of 67, the mini-splits have been able to maintain the set temp of 67 with no issues. Typically they run about two degrees higher during the 10+ outside temps, but with the HRV dumping colder air into the house they don't seem to be exceeding the set temp during the extreme outdoor cold temps. All-in-all though, I can't complain. They have far exceeded my expectations.

  11. kjmass1 | | #11

    My Halcyon splits worked pretty well in the 30-45 temp range...anything above that I had crazy overshoots, and below that they tended to not keep up. I have a lot of trouble with the remote set point, short cycling, etc. Sizing may be an issue as well. I have the communicator board and remote thermostat ready to install but want to wait for higher temps for my HVAC guy since we have to take the unit off the wall. I'll update after I have some time with the remote thermostat since I think that is half the battle.

    My basement is 55 degrees so if I can get the sills insulated I'd imagine that would help out big time as well. I'm back to my cozy steam system through this cold snap.

  12. Expert Member
    Dana Dorsett | | #12

    [deleted double-post]

  13. Expert Member
    Dana Dorsett | | #13

    It's going to take more than insulating the sills to raise the basement temp during bitter cold temps (thought it's at least a start). The basement walls need to be insulated too. Without a heat source down there it's not likely to rise much, but if it's maintaining 55F even without the sills/band-joists and foundation insulated it will probably be north of 60F at least, which makes a real difference in your actual heat load.

  14. calum_wilde | | #14

    R60 attic
    2x6 walls with "R20" batts
    R20 basement walls
    Uninsulated slab (it's a work in progress)
    1.0 ach50

    We have two RLS3Hs a 15 and a 12, just one head each.

    The lowest temp we experienced was -18°C (~0°F) for about most of the night and well into the morning. The temperature dropped from 19.x°C to about 18.2°C. Other any lower than that and I'd likely need the baseboard electric heaters to stay comfortable, maybe just a couple of rooms to help things keep up, but so far I'm esctatic with the ductless minisplits..

    Edit: The original design heat loss was 23202BTU/H at -18°C. The only things I've done to effect that are increasing the attic insulation from R40 to R60 and air sealing from an unknown leakage alrate down to 1.0.

  15. WLSchebaum | | #15

    Keeping pretty cozy here in VT the last couple days as we churn through our first winter in our house. We've got 2,000 sqft of conditioned space. First floor walk out basement with 3" sub slab foam, R30 foundation walls, R40 framed walls ( same for upper two floors), R60 roof. .7 ACH. House is a simple three story rectangle. We've got a Mitsubushi Hyper Heat multi-zone system with one 18 head in the basement and one 24 on the main floor, nothing on the top floor. Also have a small woodstove as well. We've mainly been heating with just one fire in the afternoon/evening and letting it die out overnight and then bumping the heat pumps in the morning to get it quickly back up to temps. Also just letting the basement be what it naturally acclimates to at around 58. Lately though we've been keeping the heat pumps running to do the morning bump but mostly maintaining them around 65. They seem to work great so far. I haven't tested out the pure heat pump with no fire combination just yet but the more I read here the more tempted I am.

  16. GBA Editor
    Martin Holladay | | #16

    Everybody seems pretty happy with the cold-weather performance of their miniplits, with the exception of Kjmass1, who reports (in Comment #11) that a Fujitsu Halcyon system "can't keep up" when the outdoor temperature drops below 30 degrees F.

    Kjmass1, it sounds like either (a) your minisplit is seriously undersized (due to a bad heating load calculation) or (b) there is something wrong with your equipment.

    I would definitely call in a service technician to figure out what's going on.

  17. calum_wilde | | #17

    Martin, I need to make a correction of my original report. It was -18C again last night, the difference is this time I turned the basement unit up to the same temperature as the main level unit to even the load. The house was warmer than I expected it to be and the upstairs unit was cycling on and off, clearly having no trouble keeping up. I'm confident they would still work well with this heating load to an even lower temperature.

  18. WPmichael | | #18

    Out of curiosity I thought once a temperature has been reached these heat pumps stop operating, for instance with Mitsubishi is set at -13 F. But I notice many of these post had temps below this. Is this not the case?

    North of NYC it reached 0 F, I have 2 Mitsubishi MUZ-FH12NA Hyper heat 12k units and both put out adequate heat to keep the room where the head was located at 70 degrees. The adjacent room where a bit colder but by no means unbearable. These units have exceeded my expectation in the amount of heat they produce at single digit temps.

    I installed a wireless sensor ( it does a much better job keeping the desired room temp, compared to the built in sensor in the wall mounted unit.

  19. Expert Member
    Dana Dorsett | | #19

    WPMICHAEL: The specified "cut off" for Mitsubishi units is no warmer than -18F (though most will still be running in to the -20sF), and specified to automaticaly re-start by the time it warms up to -14F. The fine print on the submittal sheet for your FH12 reads:

    "System cuts out at -18º F (-28º C) to avoid thermistor error and automatically restarts at -14º F (-26º C)"

    Find it under the red bar labeled "Operating Conditons (Outdoor Intake Air Temp.) (Max./ Min.)" on the left column of the first page:

    I couldn't find a comment on this thread indicating a Mitsubishi operating below -18F, did I miss it?

  20. WPmichael | | #20

    Thanks Dana, it was post 7 that caught my eye it was Fujitsu operating at -24, assuming it was Fahrenheit, I believe Fujitsu operates to -15 F. These types of temps are not a concern for where I live. But just an engineering curiosity that these units can still produce heat at a bone chilling -24.

  21. lance_p | | #21

    @ Calum Wilde

    Thanks for your detailed info. Can I ask a little more detail about your setup?

    1. 2400 sqft, assuming from your post this is a bungalow. Is this a 1200 sqft bungalow with a full basement, or a 2400 sqft bungalow with a full basement?

    2. Two RLS3H's, a 15 and a 12, one on the main floor and one in the basement. Which one is located where?

    3. In scenario one where your house was a little cool in the morning, what were your temperature setpoints for the basement and main floor?

    4. In scenario two where your upstairs unit was cycling on and off, do you mean it was modulating to lower its output, or was it shutting off completely?

    5. At what temperature was your designed heat load of 23202 BTU/hr determined?

    5. Where are you located? Has it gotten colder than -18C while you were using your heat pumps?

    I'm particularly interested in your application as our planned build will have a similar heat load to yours, roughly 25k BTU. Thanks for the info!!!

  22. Expert Member
    Dana Dorsett | | #22

    WPMICHAEL: Fujitsu units keep operating at arbitrarily low temperatures and do not turn off. The lowest temperature at which they have a specified-guaranteed output capacity is -15F, but that doesn't mean it stops.

    Similarly, the lowest temperature in the capacity tables for Mitsubishi H2is is -13F, but they are still operating at temperatures below that, even though the manufacturer doesn't specify the output capacity at those lower temperatures.

    I believe Gree's Crown Plus models have a specified capacity sown to -22F (wet-bulb) temperatures.

  23. kjmass1 | | #23


    Just wanted to update that I finally got a Fujitsu certified tech out and he came across some issues with the original install. I now have my main first floor unit hooked up to a wired controller and it is night and day with how it behaves. It will actually keep a set point and the constant cycling seems to be over. It also seems to do much better modulating fan speed and operating quieter.

    This weekend will be a good test with some lows in the 20s and snow in the forecast.

    He also had no issue with the unit being ~2" from the ceiling. With the temp being sensed from the thermostat it's not as much of an issue.


  24. CMObuilds | | #24

    That's great no one is freezing to death, bigger question is what do these units cost to run when they are in a real prolonged cold snap?

    And will they keep an even 70F day and night or do they slip at night and recover during daytime hours?

    Anyone have data on a furnace vs minisplit operating cost ignoring install costs?

  25. GBA Editor
    Martin Holladay | | #25

    T. Carson,
    There have been lots of studies of minisplit electricity use. To generalize broadly, the annual average COP (efficiency) of these installations ranges from a bit over a COP of 3 in climates without very severe winters, to a COP of about 2 in very cold climates.

    To compare to natural gas, propane, or oil, you have to make some calculations.

    In most locations, natural gas will be a cheaper fuel than electricity. With fuel oil, the calculation depends on the price of oil and the price of electricity.

    If you live somewhere with inexpensive electricity, a minisplit can be quite inexpensive to run. The higher your electricity cost, however, the more likely it is that natural gas (or even oil when the price of oil is low) will save you money.

  26. JeremyArch | | #26

    T. Carlson

    I can give you a little breakdown on my all electric house. On a monthly base from the end of March 2017 to the end of Oct 2017 my house averaged 23 KWH a day. That is without air conditioning through the summer and I take that as my base load for my family of 4 in a 2100 sq foot house.

    We had two Fujitsu XLTH (a 12000 btu and a 15000btu) installed at the end of august after some air sealing work, attic insulation, new triple pane windows and patio doors and exterior rigid foam. Not Pretty good house levels, but definitely better then average.

    When heating season began Oct-Nov over 29 day bill cycle we averaged 33 kwh per day, 10 of which I assume to be miniplit operation or 290 kwh for the month. Our delivered price of Electricity is 0.14c/kwh. It cost us about $40 to heat the house

    Nov to Dec over a 30 day billing cycle averaged 38 kwh house, 15 per day for minisplt or 450kwh for the month. It cost $63 to heat the house

    Dec-Jan over a 33 day bill cycle average 43 kwh per day, 20 for miniplits of 660kwh. It cost me 92 bucks for the month which had some pretty cold temps.

    I also burned a cord of wood during those 3 months in my woodstove, mostly because i like to have a fire in the evening when im watching a hockey game which cost about 300 or about 100 a month. I dont know how much this affected my mini-split use.

    My father in law lives 10 minutes away, has a newer house about 3000sqft and spent 500 dollars on oil for one month for his furnace, he was travelling for about half that month.

  27. wisjim | | #27

    We have 2 Fujitsu Halcyon units in our over 100 year old farmhouse. We installed them to provide heat in the shoulder seasons, fall and spring, when our wood furnace (forced air unit in our basement) would otherwise have a smoldering fire that tends to creosote the chimney. We shut off the mini-splits in December when we have used up our surplus solar-generated electricity, and restart them in March when the weather has warmed up. My wife prefers to burn wood over paying an electric bill. Our utility credits us with Kw-hrs of surplus energy until the end of the year and then pays us for our balance at the rated of avoided fuel cost which is perhaps a fourth of what they charge for energy, so we like to use up our surplus by the end of the year. Our PV system takes care of our normal usage, our electric car charging, and AC and heat until mid December in the fall and heat again after March or April. More PVs may increase our usage of our mini-splits. They seem to work well in the last week of December last year,, when our highs didn't reach zero F and our lows were near minus 20F.

  28. kjmass1 | | #28


    With my 2x oversized, 30+ year old steam boiler, $1.5/therm and $.20/kwh, I saw about 30% savings in temps above 30. With the recent cold snap in January in New England, I switched over to radiators since we were in sub zero temps. Kinda the best of both worlds, but I put them in sized for AC, and they aren't super efficient models.

    Put it this way, one therm or one full hour of burn time with my boiler would net 152K BTUs for $1.50.

    For the same price, a CoP of 2 would net 51K BTUs, a CoP of 4 would net 102K BTUs.

    Gas is usually much cheaper, and we pay one of the highest rates/therm in the country.

  29. CMObuilds | | #29

    @kj, thanks, good info. electricity is pretty spendy for you too I see.

    @Jeremy, curious where you are at or what climate zone you in?

    The minisplits are getting pretty popular as supplemental systems in my neck of the woods for occasional use spaces that would be hard to duct like above garages, pole building man caves, 3 season rooms, and the like. The HVAC guys seem to use them as problem solvers.

  30. JeremyArch | | #30

    @T Carlson

    I live in southern Ontario, a couple hundred km east of Toronto. Climate zone 6, though i think it is the warm edge.

    Last winter (our first in the house) we didnt use the electric baseboards and heated exclusively with wood, we went through about 4 cords from fall through to spring with a fire going often. It was a pain even though it was a fairly mild winter. This winter was much colder and the minisplits kept up nicely, some room variations but i never had to walk around in a sweater and slippers.

  31. RainR | | #31

    I have Mitsubishi hyper heat MXZ-8C48NAHZ made for 8 zones. I have 7 hooked up and was running 3 units at 68F. During the recent cold snap -10 with winds -20. The units struggled at the -13F as stated on the manuals. The rooms dipped down to 55F. As soon as the temp rose above the -13F the house returned to a normal and comfortable 68-70. I keep the set points at 66F and the temps average 68F. I have every model because of the large complex home. My question and concern is my electric bill. It was reasonable until now and I had the same issue last December 18-January 18 billing. Cost was 3 times the other months. $220 to $660! Can it be this huge Hyper Unit running in the winter? I will trouble shoot with circuit breakers to figure this out. Seems insane but same exact increase in electric bill same period and no I don't light up the house crazy with Christmas lights. Any others seeing the same?

    1. amacoolone | | #33

      I had the same issue recently. My normal bill with the heads is around $200, but that jumped to $450 for the period Jan 15th to Feb 15th. It was cold in Seattle for that period, but we also dropped the set temperature by 5 degrees or so and bumped up the use of our large gas fireplace to heat the house. Not sure what it is, but interesting you mentioned if it could be the Hyper Unit thing as we do have those units. Were you able to figure it out?

      1. Expert Member
        Dana Dorsett | | #34

        The COP efficiency at Seattle's typical wintertime temperature averages is about 3.5-4, but when it's below +10F it's about 2. Combine the lower efficiency due to outdoor temperatures with the greater number of heating degree-days for that period it's not crazy to see a doubling of the typical bill for that period in a non Polar Vortex disturbance winter month.

        To even begin to analyze it, go to and log the base 65F heating degree-days (HDD) for the comparative meter reading periods using a fairly nearby weather station. At cooler outdoor temps there will be a higher kwh/HDD ratio than more temperate periods related to the efficiency loss, but it should be a pretty smooth transition with rising/falling average outdoor temp. If your heat pump is less than half your electric use during normal times there may be a lot of noise in that type of measurement, but you can subtract out some of it by using your lowest month's use as the baseline.

        1. irene3 | | #36

          I'm also in Seattle and our total electricity bill for mid December to mid February (we get billed every two months) was $332. I figure about $227 of that was for the heat pump. Last year the corresponding amount for running the old gas furnace (which admittedly was very old and inefficient) over those two months was about $320.

  32. _Stephen_ | | #32

    My 2100 sq ft house in southern Ontario just went through a real cold spurt, with temps down to -24 C.

    Our MItsubishi PUZ-HA30NHA5 is actually oversized for the load, and plowed right through it, and at no point even modulated past ~75%. Normally, it will run at lowest modulation for several hours, then shut off for a few hours, however, when she got as cold as it has been the past week, it runs straight through and varies it's modulation depending on the heat load, which has been neat to see.

    Our modeled heat load is 18k BTU at -18C, but in reality, it appears to be closer to 15k BTU, probably due to the significantly better blower door test than was expected (modeled at 1.5 ACH, actual test came in at .6 ACH).

    Overall, we couldn't be happier with the system. It's so quiet, so comfortable, and the zoning solution means we can keep the upstairs a degree cooler than the basement.

  33. MD555 | | #35

    Installed a LG Multi F MAX (LMU480Hv) in 2016 in a 2000 sq.ft house, which is the up to eight head unit with indoor refrigerant distribution box. We are located near Duluth MN and saw -36.4F this year from our back yard weather station. With our equipment rated for a temp down to -4F it was never expected to heat the house in extreme cold weather, however I did need it to bring some predictability in my propane usage and yes we need air conditioning! I have the wireless wifi adapter installed and have been using LG's diagnostic software, LGMV, for better understanding of how to maximize energy efficiency with this equipment as it does provide amperage usage along with suction temps etc. We have no problem keeping the house at 72F down to -8F with this equipment, however after -8F backyard temp, or a suction temp reading of -6F on the equipment, defrost mode occurs every 30 minutes and the house temperature drops and amperage consumption sky rockets- then I shut it all down. 5F to -4F the equipment will consume between 1500 to 2500 watts with basement head (12Kbtu wall unit) in heat mode and two upstairs units in blower mode with pass through heat from the distribution box.

    1. Jon_Lawrence | | #37


      How would you describe the modulation capabilities of your multi zone system? Does it seem like the indoor units only operate at their rated capacity or do you think they operate at lower levels like a single zone system can?

      1. MD555 | | #38

        The indoor parts of the system include heads hanging on wall, or ceiling, which connect refrigerant and power/communication lines to the basement distribution box also known as the EEV (electronic expansion valve). From the EEV two refrigerant lines and communication/power connect to the outdoor unit. The EEV modulates the refrigerant to each individual head and does so based on its own program logic, but the longer each head is on and the more temperature overshoot occurring the specific zone will modulate via EEV. Temperature exhausted from each head will be greater if the system is trying to achieve a a user target temperature and coordinating EEV steps are shown on LGMV software. The system allows 8-10 degrees of overshoot so as each head enters temperature overshoot the EEV walks back and the exhausting temperature will moderate. To prevent oil pooling the system will slightly open each EEV for each zone whether the unit is calling for heat or not. This benefits the user because the head can be run in fan only mode to take advantage of some heat for areas that need very minimum heating. This all translates to about a 25 degree swing in air temps out of head based on EEV modulation. For example EEV reading from LGMV showing 30 steps which is the base setting to prevent oil pooling. If the fan is operated on Low fan speed the exhausting temperature will be 105F, but if I request heat from the same head (as opposed to fan only mode) the EEV jumps to 150 steps and the exhausting temperature will read 130F in fairly short order.

  34. Expert Member
    Dana Dorsett | | #39

    The LMU480Hv Multi F MAX is a 5 ton VRF unit with a 4:1 turn down ratio. Once the whole house load is under 15,000 BTU/hr the compressor will start cycling. Putting commercial VRF type distribution smarts & valving indoors rather than making it another "Multi-split Medusa" makes installation quite a bit easier too, with just one set of refrigerant lines penetrating the exterior walls. The micro-stepping while operating in a modulating range is better than the typical multi-split too.

    In late 2016 LG released the Multi V S series (ranging from 2-5 tons) is good for about a 10:1 turn down ratio (at least the compressor can modulate from 15- 150 hertz) and is fully VRF, with the ability to heat some zones while cooling others simultaneously, and can heat domestic hot water (with a "reverse indirect" as the thermal storage for that hot water.) A retrofit Net Zero Energy house in Rhode Island recently featured on This Old House used a Multi V S as the sole heat/cool/hot-water solution. There isn't much in the way of technical information in the video, but take a look starting at the 14:10 mark through 17:49 mark:

    The "S" in "Multi V S is for single-phase power. These are basically the same technology as their much bigger commercial VRF systems that take 3 phase power, but down-scaled to something applicable to residential loads. Mitsubishi has done some experimental work on similar down-sized full-on VRF in the past 5 years, but I'm not aware of any product releases. But the approach makes too much sense to believe that LG will be the sole vendor in this space going forward. Hopefully somebody will make a full cold-climate version with the necessary pan heater & controls for managing defrost water better in cold/very cold climates.

    1. MD555 | | #40

      Thanks for the link that was cool to see.

      Last year I read LG had launched the 'Red' Line LMU420HHV with advertised 100% capacity to 5F and continuous operation to -13F. From the factory came an installed base pan heater! On the LMU480hv I had to spend an additional $100 and install the base pan heater in my yard.

    2. user-723121 | | #44

      Dana; Could this LG unit (if cold climate adapted) be used as a replacement for a heating oil fired hot water baseboard system? We will be considering a boiler replacement soon at our farm, approximately 9,000 hdd, SE of Fargo, ND.

      If not this unit what other might we consider.

      Thank you, Doug

  35. Expert Member
    ARMANDO COBO | | #41

    Yup... I reeeeeeeealy do feel sorry for y'all suckers! 75° and warm toes! Best wishes.

    1. Expert Member
      Dana Dorsett | | #42

      I'll respond in greater detail on that come July. ;-)

      1. Expert Member
        ARMANDO COBO | | #43

        Touchè... :-)) To bad we can do emojis! Martin?

        1. Expert Member
          Dana Dorsett | | #45

          FYI: It was a fairly comfortable (if cooler than usual for March) +10F outside when walking the dog this morning. Being a short haired type his favorite spot on mornings like this is directly in front of the wood stove, which he prefers over the radiant floor zone despite occasional singed tip of the tail when turning around to settle down. The surrounding hearth is well above 75F (unlike the radiant floor) which feels pretty good in bare feet.

  36. jms_designbuild | | #46

    We finished our new (all electric) house in Florence, Montana right before Xmas. We heat/cool the entire house with (2) Fujitsu Halcyon 15K minisplits and an HRV system to circulate the air. (some backup bathroom heat but we only use it when we take showers). We recently had a week where we woke up most mornings to negative temperatures and 2 mornings in a row of -23F. Our living room unit (pictured below) is set to 68F and the upstairs unit in the hall between bedrooms to 66F. Both of the really cold mornings it was 62F in the living room when we got up in the morning but as soon as the sun came up the minisplit caught the temperature back up. If it wasn't a glass room I'm sure it'd be doing a better job but our house has stayed warm and comfortable all winter so far. My bigger issue will be doing a little re-grading around the outdoor unit since it's made a lake of ice that's dammed itself back up toward the house. We've got a small wood stove there as well that we use on days when it frigid outside and it makes a noticeable difference throughout the whole house when it's burning but we can manage just fine without it. The best news was that since it was sunny on those 2 coldest days our 10kW array was outproducing our usage and we were -3 & -4 kWh on those days.

    It's been informative to now live in a house with this minisplit heating system in our climate after designing & building a number of similar systems in houses for clients over the years. It takes a different understanding and expectation than your typical ducted forced air furnace or baseboard heat that is common around here.

    1. Expert Member
      Dana Dorsett | | #47

      >"The best news was that since it was sunny on those 2 coldest days our 10kW array was outproducing our usage and we were -3 & -4 kWh on those days."

      OK then! Count me among the impressed!

      This experience would indicate that in sunny locations it doesn't take huge amounts of battery, a huge overbuild factor on the PV array, or long term energy storage to end up Net Zero Energy even during the colder months. As the costs of PV and batteries continue to fall that may become the new-normal way to build houses even in locations where it's not required.

  37. user-1047104 | | #48

    Hey, I am redoing a property of mine and debating if to just have it heated via ductless. I will most likely have to get mr cool units as they are just so much more affordable and I need quite a few of them. Is it possible to have it as the only heat source (no back up) in Long Island NY weather?

  38. Expert Member
    Dana Dorsett | | #49

    I'm not sure if NY regulations would still require automatic back up systems, but it's conceivable that the Mr. Cool Oasis Hyper Heat series units could cover your Polar Vortex disturbance event coolth and still operate efficiently at your average winter temp. There isn't a whole lot of technical data on them easy to find on the web (and extended temperature capacity chart would be pretty important in locations even slightly cooler than yours.

    Even a standard AHRI submittal sheet seems to be absent from the web, though they do have AHRI certificates. We don't even know what the maximum capacity is at +17F from the available information, which may or may not be the stated heating capacity( which it must be able to deliver at +17F, but isn't necessarily it's maximum capacity at that temp.)

    It's doubtful that you "...need quite a few of them...". If you're installing a mini-split per room it will be grotesquely oversized, expensive, less comfortable, less efficient, and more expensive. A 3/4 ton mini-split would be insanely oversized for the actual heating & cooling loads of a bedroom, probably oversized even at the (not to be found anywhere online ) minimum modulated output levels. Half of the 1500-2500' sized houses on Long Island can be heated and cooled with two mini-splits, one ducted, the other ductless. Some might need three, very few would need more.

    To find out what you ACTUALLY need requires a room by room Manual-J or similar load calculation.

  39. Trevor_Lambert | | #50


    You said,

    "Fujitsu units keep operating at arbitrarily low temperatures and do not turn off. The lowest temperature at which they have a specified-guaranteed output capacity is -15F, but that doesn't mean it stops."

    Just to clarify, is that the case whether it's the RLSH (pan heater option) model or not? The lowest specified temperature for the RLS models is -5F. I'm leaning toward the RLS because of the energy penalty for the pan heater, but that kind of goes out the window if the RLS doesn't operate down to the same temperature as the RLSH.

  40. Expert Member
    Dana Dorsett | | #51

    >"Just to clarify, is that the case whether it's the RLSH (pan heater option) model or not? The lowest specified temperature for the RLS models is -5F. I'm leaning toward the RLS because of the energy penalty for the pan heater, but that kind of goes out the window if the RLS doesn't operate down to the same temperature as the RLSH."

    The non-H Fujitsu mini-splits keep going at temps well below -5F, just as the -H versions keep going well below -15F.

    There is no indication in the manuals of any temperature at which the controls turn it off, but there is vague verbiage to suggest that control algorithms of the unit "may" continue to protect itself from damage even temps below the specified operating range (and seems to.)

  41. Chonguita | | #52

    Thank you for all the amazing information. I need to buy a split unit thinking about the winter. I am looking for something close to 30000 btu. Which you consider is the best one to buy? Thank you

  42. PaDutch | | #53

    I have a old 1939 sandstone Farm house. We installed 3 ton Fujitsu mini split with 2 floor units and 1 wall unit. The house also has a oil boiler hot water heat. The mini split keeps the house warm until the temps drop in 30's. The house has R-19 in attic no other insulation only 18 inch stone walls. The units put out warm heat when 20 degrees outside. Happy with Fujitsu just wish house was more insulated but ?
    Live in Ephrata, Pa. Area.

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