What Size Air Conditioner Unit Do You Need?

  • April 29, 2020
  • By MR COOL

With summer quickly approaching, you might be wondering if your air conditioner will get you through the hottest months of the year. You need a cooling system that’s the right size for the space, uses the right amount of energy and keeps your whole house comfortable.

If you’re just replacing an old unit, the size you used previously is the best place to start. It is also important to consider the model and energy efficiency of any AC unit you might utilize. This guide can help you figure out the proper cooling capacity for your home air conditioner.

Why Is It Important to Choose the Right Size Air Conditioner?

Selecting the correct size AC unit for your home is essential for sufficient, cost-effective cooling.

An air conditioner that is too small will:

  • Run too often and for long periods, often requiring more maintenance.
  • Leave your home too warm and create hot or cold spots.
  • Supply insufficient airflow to keep your home at a comfortable, consistent temperature.

An AC unit that is too large for your home will:

  • Run for short periods without dehumidifying, potentially encouraging mold or dust mites and causing structural damage.
  • Decrease the system’s life span and raise energy costs with frequent starts and stops, requiring more maintenance and energy.
  • Run loudly compared to a properly sized system, which should be barely noticeable.

How Are Air Conditioner Units Rated?

AC units are typically rated by BTU production and by the SEER rating. While BTUs measure the cooling capacity per hour of an air conditioner, the SEER measures its energy efficiency. Typically, the bigger the cooling system, the higher the BTU and the lower the SEER.

To convert BTU to tons, keep in mind that there are 12,000 BTU in a ton. Room air conditioners have a cooling capacity as low as 5,500 BTU per hour. The cooling capabilities of our DIY ductless mini-split systems range from 12,000 to 34,500 BTU per hour. Our Signature Series central air conditioners can go up to 60,000 BTU per hour.

Use these factors to determine if you may need a more significant BTU-rated AC unit than typical:

  • Your ceilings are higher than 8 feet.
  • You live in a warmer climate.
  • You’re putting the unit in direct sunlight.
  • You have little insulation.
  • You have large windows in the room.
  • You have a large, open-concept house.

This number affects the sizing for your air conditioner because of its energy expenditure in one hour. You would need an AC unit with a smaller BTU for a compact room so you don’t use too much energy to cool your space. A cooling system with a larger BTU for a large room will also adequately cool the area.

1. BTUs

A BTU, or British thermal unit, measures the energy that your air conditioner uses to cool the room. When you count calories, you’re measuring how much energy you’re putting into your body and how much you need to burn to maintain your weight. In the same way, when you measure BTUs, you estimate how much energy your appliance can process to regulate the temperature of your home.

2. SEER Ratings

While it does not measure the size of the air conditioner, the seasonal energy efficiency ratio (SEER) number measures how efficient a central AC unit is over the summer. The higher the SEER rating, the more efficient the product.

You might also see information about the energy efficiency ratio (EER), which measures how efficient a cooling system will be at a certain outdoor temperature. The SEER more accurately reflects the overall efficiency of a unit seasonally, but the EER will tell you how the AC works during peak operations.

Energy-efficient appliances have a yellow tag that displays their SEER rating. To have a higher energy efficiency for your AC unit:

  • Schedule preventative maintenance at least once a year.
  • Change your air filters monthly to protect against debris.
  • Set a programmable thermostat to manage comfort correctly.
  • Seal and insulate windows and ducts, to prevent air leaks.

While appliances with higher SEER ratings have a higher upfront cost, you’ll save money on energy bills each month with an energy-efficient cooling system. Companies also offer rebates on their energy-efficient products as incentives to purchase them.

The minimum SEER rating for most of the country is 13. If you’re in a state that gets warmer summer climates, the score is 14, so your home could save energy and money. Some of our air conditioning units have a SEER rating of up to 23.

3. AC Tonnage

What is AC tonnage? AC tonnage measures how much heat the unit can transfer in one hour. Each ton of refrigeration can cool 12,000 BTUs each hour. Learn how to calculate air conditioning tonnage by multiplying the unit’s tonnage by 12,000. Using this formula:

  • A 2-ton unit can cool 24,000 BTUs per hour.
  • A 3-ton unit can cool 36,000 BTUs per hour.
  • A 4-ton unit can cool 48,000 BTUs per hour.

What Size AC Do You Need?

Figuring out what size air conditioning unit you need is as simple as taking a tape measure and looking at the length, width and height of your living space. You could also call in a professional to help you find the air conditioner you need to cool off the room. Use these calculations to choose the right size for your AC system.

1. Square Footage AC Calculator

How many tons of AC do you need per square foot? To figure out the square feet within your room, measure the length and width of the room. Use these tips to calculate the area of your living space:

  • In rectangular and square areas, multiply the full width by the length.
  • In triangular places, use the same formula but cut it in half.
  • If you have an abnormal room shape, divide the room into rectangles, triangles and squares and use the previous equations. Add the total square footage of all the various dimensions.

2. AC BTU Calculator Chart

How many BTUs do you need? After you’ve measured the dimensions of each room in the home where you want to put an air conditioner, you can figure out what you need based on the BTU conversion chart.

Find your room’s square footage on the left column, and then use the right column to get the proper capacity for the AC unit. The cooling capacity is measured in BTU per square foot. A 3-ton AC unit can cool a small house, while a 5-ton AC unit can cool a bigger home.

3. Make Adjustments as Needed

While this process seems pretty straightforward, you also need to make some adjustments based on these factors:

  • Decrease the cooling capacity of the unit by 10% if the area has shade.
  • Increase the cooling capability by 10% if the area is in direct sunlight.
  • Increase the total by 600 BTUs for every extra person in a room if the room is occupied by more than two people regularly.
  • Increase capacity by 4,000 BTUs if the air conditioner is in the kitchen.

4. Heat Zone HVAC Calculator

Throughout the world, various climate zones indicate the heat that each region experiences. Contractors and builders use climate zones to get the most energy savings in a home. Here are the heat zones in the United States to determine which one you live in and how it affects the size of your AC unit:

  • Hot-humid: You are in a hot-humid climate if you live in the southeastern part of the United States.
  • Mixed-humid: This climate consists of the central-eastern region of the country.
  • Hot-dry or mixed-dry: You may feel hot and dry air if you live in the southwestern part of the United States. The difference between hot-dry and mixed-dry is that mixed-dry sees less warm temperatures throughout the year.
  • Cold or very cold: In the northern part of the country, you get colder days more frequently.
  • Marine: On the west coast, the weather is pretty consistent, but you’ll see rain each month.

These climates got their names based on the amount of precipitation and the frequency of warmer temperatures compared to the rest of the country. You could figure out what type of air conditioning system you need depending on how often you have sunny days in your region. A house in a hot-humid climate would need a more powerful AC unit than one in a cold part of the country.

5. Bring in a Professional

A professional HVAC contractor will know how to size your cooling system for your living space. They can give you an in-house estimate and explain how much it would cost to install an AC unit that would work best for your living conditions.

If you’re checking out our products, you could contact an expert from MRCOOL. We offer free lifetime tech support on all of our merchandise, so if you’re ever stuck, just give us a call. After years of experience, we know where our products fit best, especially our DIY® Multi-Zone, which can cool the whole house.

Other Important Factors to Consider

While size is a crucial part of choosing an AC unit, you should consider other factors, including:

  • Type: Whether you’re sizing a mini split unit or considering a central split system, your family’s needs, such as scheduling temperatures or creating zones, determine the best type of air conditioning for your home.
  • Durability: While a properly sized air conditioning unit is essential, you also need a durable system from a reliable manufacturer to ensure the unit lasts as long as possible.
  • Maintenance requirements: Ensure you know what maintenance you’ll need to keep your AC unit in good condition, from replacing filters to scheduling professional inspections and repairs.
  • Home and insulation: If you own an old house with original or dated insulation, raise the BTUs you need from your AC unit by at least 30% to account for more heat transfer.
  • Air quality: The correct air conditioner should dehumidify your space, so look for a unit with a filter capable of keeping dirt, germs and odors out of the air and away from your unit.
  • Ceiling height: Ceilings over the standard 8 feet generally require air conditioning units with 20% more BTUs to sufficiently cool the area.
  • Fixtures: Everything from windows that let in direct sunlight and hot air to kitchen appliances that make your space warmer affects your air conditioner’s performance.

Find the Right Air Conditioner for Your Home

MRCOOL manufactures reliable, high-efficiency HVAC systems to keep your home comfortable year-round. View our map to find a MRCOOL dealer near you. You can also connect with a service technician or installer. If you have any questions about our products or what size air conditioner you need for your home, please contact our team.

394 thoughts on “What Size Air Conditioner Unit Do You Need?”

    1. Couplers to extend DIY line length beyond 25′ by combining two lines will be available this summer.

      1. My church has a sanctuary that is 7,000 sf with 22-1/2″ ceiling. Would 5 of these help our situation temporarily? We can’t afford a new system over $100,000 and looking for temporary solutions.

  1. What unit do you recommend for a 1000sqft 3 bd/1ba home in SoCal? Would one 24K work or a multi-zone 4quad is better? (1 in living area, 3 for all bedrooms) Our home is 1950s bungalow style.

    1. A 4-air handler multi-zone would definitely do the job. The 36k DIY Multi with four 9k air handlers would definitely give you plenty of heating and cooling BTUs.

    1. For an 18k mini-split you would need an appropriately rated disconnect box to wire the condenser.

  2. What would you recommend for a 200 sq ft detached garage in Texas. We are converting it to an art studio and need to make it comfortable, but also protect our supplies. There is moderate insulation in the walls. Basically a “She Shed.”

  3. Good Day from GA, We have been considering mini splits for several years as our home is over 15 years. Our 2nd central unit is on its last leg and need some advice. There are two bdrms that are always warm or hot. They are about 250 sq ft. We also have an unfinished basement that gets real hot in the summer. We are being told that installation of a mini split costs more than replacing the central unit, when the outside unit goes bad the entire system shuts down and needs to be replaced. So we are a bit confused. Could you please let us know what size we would need for units for 2 bdrms each approx 235-255 sq ft and 1 bsmnt approx. 1600 sq ft? We will not be installing ourselves and would need to contact a technician.

    1. You could use a 9k for each bedroom, and a 36k for the basement. You would most likely need a condensate pump for the basement. However, that is a just a rough estimate based on the information provided. The basement in particular might need more or less based on local factors.

  4. Are the Mr Cool DIY Heat Pump AC both AC and Heat? The name says yes to me, but there are products for air conditioning and for heat here.

    1. Most likely a 2 ton would only be sufficient if you live in Climate Zone 5. Anywhere else and you would likely need a larger unit.

  5. I’m interested in your DIY 3rd Gen E-Star mini splits. I have an insulated shop, 550 sq. ft., 8 ft. ceiling, insulated garage door. I live in Mesa, Az. And i will install the unit on the north wall so it won’t get too much direct sunlight. What size unit (model number) would you recomend?

  6. I have a 700sq ft 3 car garage in Denver CO. The garage has 11 ft insulated ceilings. All walls are also insulated. The garage doors are non insulated aluminum. Garage gets morning sun, afternoon shade and is opened/closed about four times a day. The garage has gotten up to 95 degrees in the summer and 30 degrees in the winter.

    What size Gen 3 DIY would you recommend?

  7. In south Texas on the gulf. What would you recommend for a 625 sqft garage with insulated 10 ft ceilings and insulated door. Want to pull out humidity but be able to cool the place down.

    Open door 4-5 times a day.

  8. Looking too cool an older style house attic that had been turned into a 2nd floor. House is in northwestern ohio. There is decent insulation in the rafters and modified vaulted ceiling. Floor layout is roughly 750 to 800 sq ft. Roof does get alot of heat from sun. Looking at installing 2 ton advantage 3rd gen mini split. Would this be a good fit? Also, unit I’m looking at is sold with 16ft line set. 25 foot line set would be cutting it close. Is there another line set kit that can be purchased or since this isn’t the true DIY do I just have to run more tubing from hardware store and add more r410a?

    Curious about multi units as well but the line set will be an issue for this as well. Also haven’t seen where the indoor units show what there BTU ratings are. Would appreciate some understanding on how to figure that out.


  9. We have a building that is 12’x8′ with 10′ ceilings. We will be insulating the whole building. It gets afternoon sun at the hottest part of the day. We live in the Southeastern United states and have highs near 100°F or more during the summer and lows in the teens during the winter. Do you all have a unit that would keep it cool in the summer and warm during the winter. What size unit would you all recommend? We have been researching for months.

    1. A 12×8 is certainly a more compact space than we design our mini-splits to handle. Your best bet might be a traditional window unit.

  10. I have a detached insulated work shed that is 12×16 (192 sq ft) with a cathedral ceiling. Would the 9000btu mini split be too big?

  11. What is the mrcool 3rd Gen 36k btu mini split capacity range in cooling btu’s. Knowing this will make my sizing decision much easier. Thanks.

      1. Thanks I get the high end what is the range? Low end to 34,500? what is the lowest it runs at to the highest?

  12. Hello, Mr. Cool!
    I am trying to size a 3rd Gen DIY unit for a 200 sq foot room with a vaulted ceiling, which goes from 8’ to 17’. This is a top floor space with The ceiling located right underneath the roof with no vented attic. Th roof is exposed to direct sun all afternoon and the room can get as hot as 90F in the summer. There is a single zone central air system but the room temp difference between the ground floor (where the thermostat is) and the top floor is too great for any efficient cooling of the top floor. The indoor unit will hang at the top of the tallest wall (17’) blowing cool air down.
    Thank you very much for your help.

  13. Help! We live in SW Michigan. Appx 2800 sf 2-story plus unfinished (hope to finish) basement. 4br+dining room, family room. Our current heating system is very inefficient and AC unit does not work. We got an estimate from pro for replace/ install of new furnace/AC for $15k+! It’s it feasible to DIY a whole house solution with only MRCOOL products? Can a multi- zone system completely replace the traditional furnace/AC we have or can it at least be primary and the traditional stuff be back- up? We were freezing in the blizzard-y winter and wasn’t spring. Now we’re burning up here and need to get these sorry window units out of here! I tried to find a way to order the DIY multi- zone unit, but don’t see that option. Hellllp!!

    1. You could definitely use a DIY Multi-Zone for all your cooling needs. However, if you’re in Michigan, we would highly recommend a good furnace for heating. Any heat pump, ours or anybody’s, suffer in very low temperature conditions. Your best bet would be to replace your current heating system with a new, high efficiency furnace, and use a Multi-Zone for cooling and supplemental heat.

  14. Hi,

    I live in Charlotte NC. I have a two car garage, 3 walls exposed to sun at various parts thought the day (E, W, N), the other wall is attached to the house, and there is a finished room above the garage as well as knee walls on the edges with supper attic type insulation. The garage is ~25x26ft with 9.5 ft ceilings; dry walled with 19880’s 1/2 inch wall board behind it serving as very, light insulation; new insulated garage door; one east facing window (double pane and low e) ; and one half light door facing with normal glass facing SW/W. How many BTUs would you recommend in the Gen 3? I am not sure if 12k is enough, afraid 18k is too much, and think anything over 20k is for sure too much. What is your recommendation?

  15. I have a 30ft. by 40ft. pole building that is my garage and woodshop in south Texas. It is very well insulated with foam on all walls and roof and the two 10 x 10 garage doors have Styrofoam insulation. In the 100 degree heat of summer, it will get up to about 88 degrees in the garage. Heating in the winter is a non issue as the coldest day we have seen was only 26 degrees and I kept the garage at nearly 60 degrees with 2 halogen flood lights. If I closed off the open area above the 11 ft. high rafters, do you think I could get by with a 24,000 btu diy mini split to cool the rest of the area to below 75 degrees in the heat of our summers?

    1. You might be able to get by with a 24k. It’s hard to say without doing a Manual J. What do you have in place that is maintaining 88 degrees in summer?

      1. Just a heavy layer of blown in expanded foam insulation, insulated steel doors and garage doors, and no windows.

  16. Hi, I have a game rm attached to the main house that is 550sq ft. The rm is next to the kitchen with just a counter separating the rooms. The game rm is typically over 90f in this South Florida heat. The main part of the house has central ac but does not cool the game rm even when set to 70f. The ceiling in the game rm is 8ft with no insulation, I want to keep the rm at 78f. What size should I buy 18k or 24k.

  17. I am looking to size a Advantage 3rd Gen mini split unit for an attic turned living space. 750 sq ft with sloped ceilings and open stairway to 1st floor. Walls and ceiling have some insulation, but not great. 1st floor AC doesn’t cool entire 1st floor and thinking about going with 24K unit to help counter heat coming up from the 1st floor and cooling dropping from 2nd floor.

    Does this seem like a good option? Will eventually add another minisplit in kitchen to help 1st floor after remodel.

    1. With poor insulation, a 24k could be the right choice for that space. Since you plan to install the Advantage, you should consult with the installer before you settle on a particular size.

  18. If an 18,000 BTU condenser feeding one air handler is needed to cool a 900 sq. ft. space , would a single 18,000 BTU condenser feeding two air handlers be the correct size to cool two 450 sq. ft. spaces? Or, would a larger condenser be needed since there are two air handlers?

    Thank you.

    1. The overall cooling capacity of an 18k condenser will be the same regardless of whether you have one air handler or two.

  19. Hello Mr Cool
    I have 2 rooms I would like heated/ cooled. One is 17×14, the other is 15×15. Which DIY unit do you suggest?

  20. I have a log cabin in upstate NY that is approximately 22′ x 23′ and is a 2 story. Half of the downstairs (the Living Room) is an open ceiling 19″ tall and the there are 2 loft bedrooms upstairs (no walls overlooking the Living Room). I am not sure whether to go with the DIY 18,000 BTU or the DIY 23,000 BTU?
    I also would like some guidance on how high up the wall in the Living Room I should mount it and which wall?
    Thanks for the help!

  21. Can I order a 12k btu diy mini split with a 10 ft refrigerant line rather than 25 ft and a 230v instead of 115v. Thanks

  22. I’m looking to cool a 40×36 garage with 10’ ceilings, it is very well insulated. Heating is not a concern as I already have a source for that. I would use the dehumidification feature through the winters though. What size system would you recommend for this application?

  23. Aloha,
    I have decided to purchase a Mr Cool diy for our living room/kitchen area. We live in Maui, Hi and our living room and kitchen is on the second floor. The total sq footage of this area is 800 sq ft and that includes the stairway area and first floor corridors. The living room/kitchen entire front wall has windows facing the setting sun but we have awnings that shade them. Generally they will be only two people utilizing the area. Ceiling height is 9 feet and walls and attic are insulated. Would you reccomend the 24000 or 34000 btu unit? Thankyou for your response. Ed

  24. Yes sir I have upstairs bedrooms that are 12×12 2 of them. And a bathroom 8×12 . With some insulation. One small widow in each bedrooms. What do I need to cool and heat . I live in north Mississippi. Hot and humid summers 90-100 degrees in summer average low 20s in winter.

  25. Any prediction when the 3rd gen 12k mini split kits will be back in stock?
    I need two of them and no one has them in stock.

    Also, two 12k units appropriate for two rooms about 350sq ft each in a warmer southwestern climate?

    Thank you,

    1. The DIY 12k should be back in stock now. Two 12k units should be sufficient for two 350 sq ft rooms.

  26. I,Am Interested In Installing A Mr. Cool System Into My Home..My,Home Is 1056 Sqft…
    My,Home Is 70 Ft Long X 16 Ft W… What,Size Would You Recommend ?
    Thank You..

  27. I want to purchase Mr cool duckles sprit
    Ac unit DIY
    I know it come with 25 ft of pre charge line
    But It’s little bit 10ft short line
    I like to purchase 35 ft or 10 ft extended
    Can you do that for me?

  28. Hello Mr Cool,
    Cool of you to answer our questions. 🙂
    I live in New Orleans and have a 1200 sq ft Shed to cool. Metal roof with 2″ of closed cell foam. Right now the walls have no insulation. The floor is concrete. The ceiling is 9ft hight at the wall and 13ft high in the center. There is one regular sized window and I was planning on putting in a large decorative transom. It’s in full sun all day.
    What size Mr cool should I get?

  29. Hello I have 4 rooms I need to cool. 1 15×14, 2 11×10 and a big 24×15 room. What size do you suggest I get?

  30. I’m looking for a compressor and handler with heat pump split system. At least 16seer and preferably dual speed. I’m Looking to cool/heat 2200sf (a well insulated two story home). What would you recommend and would the cost be?

  31. I have two rooms which are both 15′ x 30′. Which size multi-zone condenser and two air handlers would be best?

    Also, I need to mount one of the handlers above a window which only has a 14.5″ space between the top of the window and the ceiling. How critical is having some extra space above the handler? Would only having 3″ above the handler be a show stopper?

    1. It sounds like you would want at least a 12k air handler for each room, and at least 24k BTUs overall. We recommend you follow all clearance requirements in the installation manual for best performance.

  32. Hello,
    I live in an approx. 870 sq. ft home and here are the measurements for each room:
    Livingroom: 18 X 14
    Bedroom 1: 11 x 11
    Bedroom 2: 11.5 x 11
    Bedroom 3: 15 x 18
    Hallway: 2 x 9
    Kitchen: 8 x 10
    We currenlty have a wall AC (12K BTU) in our livingroom that works okay. We leave our bedroom doors open and it helps cool down the bedrooms also after AC is running for an hour or two, which has been working for us but we defnitely want our house little more comfortable. I can’t decide whether I should have a single unit MrCool 24K BTU installed in our livingroom, or have two units (12K each) installed in a bedroom and livingroom.
    Which would do you think would be suitable for our home.
    I thank you in advance for your help.

  33. I was wondering which MrCool Universal split system would work the best for my home; 2-3 ton or 4-5 ton? My house is just under 1650sf.

  34. I have a 7’ x 13’ camper with 6’ high ceiling. It is poorly insulated and windows are single pane. Is a 9000 BTU unit too much?

    1. In terms of raw square footage, it is definitely too much, but poor insulation and windows do play a big role. For a camper that size, I would probably go for the smallest window air conditioner I could find.

  35. This may sound like a strange question – but I have 2 DIY systems a 24000 20 SEER and 36000 16 SEER, we had a mishap in the room with the 24000 system and broke the inside unit. We’ve just remodeled and no longer need the 36000 in area of the house it was used for. So can I take the inside 36000 unit and replace the 24000 inside unit with it (keeping the 24000 outside unit)? if so, what would the SEER be? We really don’t want to change the outside units unless we REALLY have to.

  36. I have a 16w x 60L x 10 h. 960sf Well insulated , 5 low E window , 2 36 x 72 walk though doors Which unit Would work best. Live in SC.

    1. You would likely want at least 24k BTUs. If you’re aiming for a DIY installation, the DIY 24k would be an option.

  37. Hi Mr. Cool,
    I want to AC my garage with a minisplit. 480 Sq ft with 8.5 ft ceiling. South exposure in Oklahoma. 3 walls and ceiling have no insulation, but I could insulate the ceiling pretty easily. 77-78 degrees would be all I need. Would the 12K BTU unit be enough?
    Also, is 16 ft the shortest precharge line available? Many thanks.

    1. 16′ is the shortest DIY line available. The DIY 12k should work. We highly recommend ceiling insulation.

  38. I have an insulated garage that’s 12×24 with a 14′ vaulted ceiling. Insulated garage door and a single high efficiency window.
    I was considering the 18K unit but want to be sure I don’t over or under buy.
    I’m in Florida, the outdoor unit would be in a mostly shaded area.

  39. I have a 1k square foot rambler, 3 bedrooms and all 3 rooms are on one side of the house, living room garage and kitchen in the other side. Would one unit cool my whole house or do I need a multi zone?

    1. A single mini-split can cool a much larger and more complex area than people think. However, a multi-zone is preferred for a space with lots of internal divisions.

  40. It seems extremely difficult to purchase a MRCOOL ductless mini-split in Canada online or at a retailer. Is there a Canadian online retailer you can point me to?

  41. I already have a HVAC unit but our upstairs bedroom is always on the hot side in the summer making it uncomfortable to sleep. We also have an attached garage (insulated well) that has no air. I was looking at possibly installing a Ductless DIY 2 Zone Mini Split and can’t decide what is best. The bedroom is 23×12 with a vaulted ceiling of 8′ upwards to 20′ at the highest point (but does have air established. Just not enough). The garage is 20’x22′ with a 10′ ceiling. Your help would be greatly appreciated.

    1. One of our DIY 18k multi zone mini split systems with two 9k air handlers could be sufficient for your needs depending on where you live.

  42. Hello – My room is 30′(L) X 20’X (W) 16′ (vaulted ceiling). Can you please tell me which size mini-split would be best for this? Thank you!

    1. One of our 18k units should be sufficient depending on where you live. Our DIY units are meant for homeowner installation, and the rest of our units must be installed by an HVAC technician.

  43. Can the precharge lines and drain line be run down the inside wall of my garage and then out to the outside unit, as the unit would be on the front of house. I would not want to run lines down front of house on outside.

    1. Theoretically, but since you need your unit to remain flush to the wall and the lines are on the back of the unit, it would be difficult to configure. Customers have installed it successfully before with an alternate direction of the line set. You can give us a call at 270-366-0457 to be able to explain your situation to someone so we can help to figure out the best solution for you.

  44. We have a 23’ x 23’ detached garage that we have insulated & have barnwood on the walls. Ceiling is 8’3” high. We’re in Missouri & this will be our home gym. What size ductless mini split do you recommend?

    1. With a square footage of just over 500, you might want to take a look at either the 12k unit or the 18k unit. A 12k typically covers up to 500 square feet, and an 18k typically covers up to 750 square feet.

  45. We have a 23′ x 23′ detached garage that we have insulated and put barn wood on the walls and drywall on the ceiling. Walls are 8′ tall, we have one window facing south and are in Missouri. We are going to use the space for a home gym. What size ductless mini split should we get?

    1. With a square footage of just over 500, you might want to take a look at either the 12k unit or the 18k unit. A 12k typically covers up to 500 square feet, and an 18k typically covers up to 750 square feet.

  46. hello,seeing what size btu for a detached garage 30×50 (1500 sq feet) insulated with 14 ft high ceilings. Live in Southern Kentucky..thank you

  47. Does your system really provide enough heat in the winter without a back up source? We are senior citizens and currently have propane heat, and need to keep our thermostat around 72 F. We live in Northern NJ so our winters are not harsh as ND but we do get our share of cold days.

    I’m familiar with Heat Pumps and used them in NC.,Those days where the temp would drop below 37 F our electric strips would come on and our electric bill was outrageous.

    1. Our DIY units won’t function under 5 degrees Fahrenheit. If you’re looking at mini splits, you may want to consider the Olympus Hyper Heat line, which was made with heating in mind. All Olympus products must be installed by a technician though, as they are not DIY. You might also want to take a look at our Universal Central Heat Pump split system, which can continue producing heat unaided down to negative 22 degrees Fahrenheit. If you experience temperatures more intense than that, like negative 37 F, you would probably want to consider one of our heat kits on this unit.

  48. Looking to install your unit in my screen in deck. We have UV screens installed which means it doesn’t allow free flowing air very well. We live in NC, we get the humidity and heat. Not looking for unit to maintain the deck temperature like a room inside the house, not a reality with screens all around (enclosed) the deck. Looking for something to just make it more comfortable when we’re out there for a few hours each day all year. Comments/suggestions welcomed

  49. Are there any DIY 3 Zone ceiling mounted systems? I want to heat, cool and dehumidify a 1,100 SQFT finished basement that currently has ceramic wall units for heat and no AC. I really don’t like the look of the wall unit boxes.

  50. So a milti zone mini split. If I
    Only wind up running one of the three units most of the time and use the other two very rarely, is this OK? I will only use a portion of the compressor capacity most of the time but this should be fine with your DC inverter arrangement without affecting expected lifetime?

    And, will I maintain the same 22seer efficiency when I use one 1/3 of the unit most of the time? Or, are the efficiency umbers pertain to full use of the system?

  51. Live in western oregon…need to replace 5 ton trane 16xi due to compressor failure…3200 sq ft house ducted. Air handler and coil matched to 5 ton trane with ecm fan and 410 refrigerant..believe lines are 3/4 maybe 1 inch…will your universal 5 ton unit work with my air handler coil etc in this enviorment thks

  52. Can I put the lines supplied with the unit inside the wall. It would be an exterior wall with insulation. It would dramatically help me in the routing of the lines.


    1. The unit will function fine that way. The only thing we recommend is that you make sure your local codes allow such an installation.

  53. I am installing a Mr Cool unit in an attic bedroom in the mid-Atlantic. The roof has new insulation but less than recommended (r-19) and gets full sun all day. The space is only about 300 sq/ft but very hot. I am debating between the 12k and 18k unit, what would you recommend?

    1. That is really hard to say. Since we use a variable-speed compressor in our mini-splits, oversizing is not as major an issue as it used to be. You may want to go with the 18k.

  54. I want to cool a workshop that’s 48 feet long, 24 feet wide, and with a 14 foot ceiling. I have one window on the south side that’s 4 feet by 4 feet. The east side of the shop is shaded, the south side is not shaded (24-foot exposure), and the west side is an interior wall (i.e. shaded) with an unheated, but insulated space. The exterior walls (north, east, south) are insulated to R19, the interior wall (west) is insulated to R13, and the ceiling is insulated to R60. I have radiant heat in the floor and live in SW Ohio. What do you recommend?

    1. The best thing to do is to contact a local engineering firm to have a Manual J heat loss/heat gain calculation performed. That will tell you exactly what you need. For that size space and your climate zone, our best guess would be something with at least 24k BTUs.

  55. Does the exterior hole need to be immediately next to the inside air handler? I need to run about 15 feet of the hoses along the inside wall to get to the proposed exit hole
    Will a 12K unit be large enough for a 550 sq ft garage?

    1. It does not have to be immediately next to the inside air handler. A 12k could be large enough for a space that size depending on climate, insulation, and other factors.

  56. I am interested in a DIY mini split multi zone system for a downstairs and upstairs of a cottage. The downstairs is around 440 square feet and the upstairs is approximately 290 square feet. Which unit do you recommend. What amount of power is needed?

    1. You would most likely need at least a DIY 18k. You might need more depending on climate, insulation, and other factors. It is a 20 amp, 240v unit.

  57. hi, I’m replacing a 3.5 packaged unit with a MRcool universal Series- MDU18024036 . The property is a 1250 sqft home in zone 2. I’m also considering replacing propane with electric. Please provide your recommendation and feedback on the following:
    – Is the 3 tons adequate? what size of electric heat kit?

    1. A Universal on a 3 ton setting might be sufficient depending on your home requirements. In zone 2, replacing propane heat with a heat pump like the Universal is likely sufficient. We have 5kW or 8kW heat kits for the Universal 2-3 ton.

  58. Does the 18k BTU 3rd Generation DIY Ductless Minisplit come in two boxes or three? I received 2 boxes, an air handler & the compressor but wondering if there’s a 3rd box with the line set. Any guidance is much appreciated. Also, if I need to contact someone to get the 3rd box what’s the best method? Thanks!

    1. Your unit should have come with a line set. We apologize for this inconvenience. Please give us a call as soon as possible at 270-366-0457.

  59. I see the term “living area” a lot. Can a living area cover multiple rooms? Would a 9+9+9+12 multi-zone DIY system cover a 1600 square foot 4/2 2 story well-insulated (2 inch closed cell plus fiberglass batt insulation) home, or would I need more?

    1. Any multi-zone DIY system offers a multitude of installation options. Normally, DIY systems work best when all of the air handlers are positioned in ways that cover the widest expanse of area. This specific model of multi zone DIY usually covers around 1,500 to 1,800 square feet. Our 9k air handlers are great for spaces under 500 square feet, and our 12k air handlers normally cover areas around 500 square feet, so you would want to plan out what you think the best location is for each of the air handlers. The climate you live in is also a factor when deciding the correctly sized unit. If you live in a relatively temperate climate, this system should work normally. If your climate is particularly hot or cold, you may want to consider a system with higher BTUs. In short, heating and cooling a home with this specific DIY multi zone system is possible, with thorough planning.

  60. I am interested in a DIY mini split system for an attached and finished (light insulation) garage without windows. I’m installing computer electronics/ projector for a golf simulator in the garage that requires operating temperatures below 80-85F. The garage is 415 square feet and located in a hot and dry climate (Tucson, AZ) Which unit do you recommend?

    1. Any insulation is definitely a plus! Normally, the 12k DIY covers spaces that are around 500 square feet. This could potentially work, but if you’re worried about the climate in Tucson being too much, you can definitely take a look at the 18k, which normally cools spaces around 750 square feet.

  61. I live Massapequa, New York on Long Island. I have a 800 sq. ft. (32x24x8ft high ceilings) 1st floor open floor plan which includes the kitchen. The house is well insulated (R-13) in the outside walls with 1” foam board outside under vinyl siding. I have a southern wall (32’ Long) that gets sun all day with 2 4’x4’ windows in it. Would the DIY 18000 BTU unit be okay or go with the 24000 BTU unit. Temperatures can reach into the 90s’ and humid during summer. Thanks

  62. I’m looking at a DIY multizone 36k for three rooms, but I’m worried about the heat output in the winter. How well does the DIY do in the winter to produce heat? Is there an average minimum temperature I should be looking at before deciding that a DIY wouldn’t be appropriate?

    1. The DIY Multi-Zone can heat down to -13F. However, it definitely performs more efficiently in mild weather. If you don’t have extreme winters, a 36k could be a great fit.

  63. Looking at your DIY split units for heat and air conditioning a roughly 300 square foot work out gym with low vaulted ceilings. There is only one 115 volt 20 amp spot left in the elecrical panel to power the unit. Do you have a suitable unit to meet these requirements? I’m in California on the central coast in Santa Barbara North County in the 93460 zip code. The room has one big west facing window and is insulated R19 walls and R30 ceiling.

  64. I have a 1200 sq. Ft. Garage insulated with r13 in the walls and r38 in the ceiling. It’s one large room located in zone 4 eastern Atlantic. Will the DIY Gen-3 23,000 BTU 20 SEER ENERGY STAR Ductless Mini Split Air Conditioner & Heat Pump work for this application?

  65. Hi, I live in San Diego and have a 760 square foot 2 bed/2bath home with open floor plan. The ceiling are low and the house is quiet small and cozy. Would a single 12,000 BTU be acceptable in this climate?

  66. I live in a cold climate in Iowa and have radiant heating in my fully insulated pole barn. It is 30x40x12 and i will most likely need ac only but am curious how cold outside will the heat work if my radiant heat goes out i need a backup of some sort.


    1. If you’re looking for a central system, you might be interested in our Universal system. It performs extremely well in cold climates, with a 100% heating capacity at -5 degrees. You can easily enter your square footage into the sizing tool on https://mrcooluniversal.com/ to see what unit you need.

      If you’re interested in a mini-split, the DIY 36k might work for you. It does lose efficiency in colder climates though, so you might want to consider the Olympus Hyper Heat, although it must be installed by a professional, and the largest size it comes in is 24k. You can find more information on DIYs here: https://mrcooldiy.com/, and you can find more information on the Olympus system here: https://mrcool.com/olympus-hyper-heat/.

  67. I have a 945 square foot garage/gym to be cooled and heated. The space has 10ft ceilings. Would the 2400 BTU be too large?

  68. I have a boiler for heat, but window ac units for summer temperatures. It gets really humid where I live during the summer months. I was thinking of the Mr Cool for the summer months. However, I won’t be needing it for the heat during the winter. The first floor of my house is 960 sq ft. What unit and size would I need to cover that space?

    1. You would likely be best served by an either 18k or a 24k mini-split. If you live in a warmer climate like the South or Southeast, go with a 24k. If you live in the North, an 18k will probably be sufficient. Should you want to do the installation yourself, our MRCOOL DIY ductless products would work best. Otherwise, the MRCOOL Advantage mini-splits could work, but they do require professional installation.

  69. Hello – Would the 12K BTU unit be too powerful for a 260 square foot space with a ceiling peak of 16 feet? What other options should we look at for something smaller? Thanks so much.

    1. I forgot to mention, the space has a few windows, (not huge) and the unit would be located in a primarily shaded area.

    2. In terms of sizing, it is hard to say for sure, since more than just square footage needs to be taken into account. Generally, a 12k would be considered oversized for that space. But it does have higher than normal ceilings, and the climate could play a significant role particularly dependent on insulation quality. Also, our DIY units have variable-speed compressors, so oversizing isn’t actually the problem that it would’ve been with previous generation systems.

  70. Live in northeast, Long Island NY. 675 sq feet GARAGE (insulation in ceiling and some walls but two big garage doors as well) with 10-11 foot ceilings. Would like ability to cool in summer and heat in winter. What size is best?

    1. Our best guess would be an 18k, minimum, for cooling. For winter, you would likely want considerably BTUs given your climate. The rule of thumb is 40-45 BTUs per square foot in your climate zone.

  71. I have a 840 square foot garage with a 9.5′ ceiling. I’m in northeastern NC. Would you recommend an 18k or 23k unit? The line set will need to go out the left side of the air handler. Is that possible on the 3rd gen units?

    1. Yes, it can go out the left side. If you have decent insulation, you could probably get the 18k. If you don’t, I would go with the larger model.

  72. I live on northern Nevada (89506) and have a 150 Sq ft separate building I use as an office. It has an 11ft vaulted ceiling with three windows and r13 in walls and roof. Can I install your 12k DIY?

  73. I have a 476 master suite addition with 8ft ceiling. I live in Northern California and in the summer we can have up to 105 degrees and in the winter it can dip to about 34 degrees. What size mini split to you think would be best for our space?

      1. Would it be a bad idea if I bump up to the 18k just to make sure it heats sufficiently in the winter? If it would cause other issues and not be effective then I will stick with the 12k.

        I appreciate your help and guidance.

        1. In a central air system, oversizing can be a significant problem. However, our new variable-speed mini-splits are much more forgiving when it comes to oversizing.

  74. We live in Southeast OH (Athens) and are adding a 2 story addition to an older home that has an existing HVAC system.
    The 1st floor is all open, 12’x22′, kitchen and family room.
    The 2nd floor will be master bedroom and bath, again 12’x22′.
    What size unit, (presuming 14,0000BTU)? I’d prefer 1 outside unit running the 2 wall mounted interior units. They’d be placed on the same exterior wall in line with each other.

    Closest retailer?

  75. We have 950 sf one story house above an unfinished basement.
    -LOTS of windows— mostly replaced in the 1990s, 2 skylights.
    -9 foot ceilings in most of the house.
    -Mostly open concept, but one bedroom and two bathrooms are walled off (those have 7 ft ceilings.) All of those receive strong afternoon sun.
    -Good insulation in the attic, moderate in the walls. House was built in 1906.
    -House faces NE.
    -We’re in St Louis. (Zone 4a)
    – An self-inputted online manual J put the cooling load at 21,295, heating at 33,312; sensible 20,495, latent 800.

    We were thinking a 27k unit with 3 heads. But the bedroom is very small- only about 120sf. It seems way too small to need a 9k head, but we figured it would require some sort of help to stay at temperature.

    What are your thoughts? Do you think we have the unit sized correctly? Should we put a head in the bedroom?


    1. It sounds like you’ve really done your homework! There’s really no way for us to give you a better estimate without conducting a load calculation. In terms of whether or not you should put a head in the bedroom, I think I would want one. Ideally, try to position it so that it can blow air out through the doorway during the day (e.g. – when you’re not in bed).

  76. Hi,

    I have an exterior metal building (shop) in North Carolina that is 667 sq ft. The roof is quite high with it’s max height being 15 ft. It is insulated by the prior owner, but I’m not sure the R value of the insulation. It does get below freezing at night in the winter and the summers can be hot and humid (maybe around 90f for a few weeks in the peak of summer). The building gets full sun. What size unit would you recommend?

    Thank you,

  77. I’m looking at your DIY series for a 500 sqf garage in Phoenix AZ. Summers are hot and winters can be coldish. Looking to maintain 70-80 degrees year round without any significant addition of insulation. Do you feel a 12k is adequate

      1. Apparently I don’t math well. My current space is in Phoenix and is 260sqf with 9.5′ ceilings. It is insulated well but is a garage so it has three exposed walls. It has two windows and will be east facing. It will see full sun for at least half of the day. I have a 230v quick disconnect available. I did not see the 12k in 230v, is an 18k just asking for trouble?

        1. We can’t say for sure exactly what you need without seeing the results of a Manual J heat load calculation. However, given where you’re located, an 18k is probably not overkill especially if you are using one of our variable-speed mini-splits. While you still don’t want to go crazy oversizing one of these new units, the variable performance capability means that oversizing is not as major an issue as it would have been with previous generation systems.

  78. So I live in Michigan and am converting a 400sqft (16*25) barn into a extra living space. Winters can get quite cold (this week down in the negatives at night) and I plan to put in a pellet stove for my main source of heating when in the building. However, I am hoping to use a mini split for electric heat backup and keep the building something reasonable so I am not heating up from freezing temps. In addition, I still need A/C in the summer. It will be insulated and have 6 home grade windows.

    Trying to figure out what size I need to meet both scenarios… I would love to be able to use electric heat if pellet stove was out of commission. Online calculators seem to give a much higher number for the heat vs. the A/C though. I am seeing calculators that suggest 12000 BTU for AC and up to 24000 for heat… Thinking 18000 might be a good medium, Would you be able to offer any insight?

    1. While I’ve never had any experience using the online calculators, what they’re telling you sounds broadly correct. You probably do need a lot more BTUs for heating than you do for cooling. However, the only way to know for sure what you need is to have a heat load calculation performed on your property.

  79. I live in Northern California with105 summers and winters down to 35. I have a 440 sq ft studio appartment with R-20 insulation in the walls and R-38 in the ceilings. The ceilings are vaulted to 10ft from 8’ft. Is a 12k system ok? Is a 18k to much oversize?

    1. The 18k would likely be the best fit for winter heating. Our DIY models are variable-speed, so oversizing is not as much of a problem as it would be with a traditional system. In the summer, you can also run the unit in Dry mode if humidity becomes a problem.

  80. I have a 50×50 insulated metal building with 16 foot ceilings located in Northwest Arkansas. What unit would you recommend for heating and cooling of this space?

    1. For that large of a space, we might recommend more than one unit, if you’re thinking of going with a DIY mini-split. A configuration that could work for you is a 36k BTU unit and a 24k BTU unit. Check out https://mrcooldiy.com/ to see what combination of units would be the best for you. If you’re interested in central heating and cooling, we would recommend a 5 ton Universal. You can find more information about that at https://mrcooluniversal.com/.

  81. I am looking to place a mini split in my Insulated Garage. which is 20×21 with 10′ ceilings located in Knoxville, TN. I am thinking 18k but I want to be sure.

  82. I have a 14’x24’ 2-story shed/garage (336sqft first floor, 672sqft total) that I am finishing to create an additional living space for my family. I have insulated the shed relatively well, but the metal roof didn’t leave a lot of room for much insulation aside from foam board. I live at a campground in Western Maryland and summers regularly get into the high 90s and the winters drop to low teens. I purchased a 24k, but after reading this article I’m a little concerned the unit is too large. Any thoughts?

    1. It could be. Generally, a 24k unit would be used for 1000-1200 sq ft. However, that can vary depending on climate and insulation and other factors. Also, our mini-splits are variable-speed, so over-sizing isn’t as big of an issue as it would be with previous generation technology. You’ll also likely want the 24k for winter heating.

      1. In your opinion, should I return the 24k and go with a 18k? I haven’t installed it yet, it’s just sitting in the room still in the box. I am probably more concerned about the heat in the winter then I am with the AC in the summer. There is an insulated garage door on one wall which opens up into a screened porch, which we will probably use a good bit.

        1. Ultimately, it is up to you. The 24k would be good if you’re more concerned with heating, though, especially in a more northern climate. While sizing does depend on factors such as room size, climate, and insulation, our mini-splits are variable speed, meaning they will modulate their performance based on your selected temperature and the current temperature. Because of this, oversizing with this mini-split isn’t as much of an issue when compared to older units with less advanced technology.

          1. Now I’m having an issue with the fact that the studs in the wall are 16” apart rather than 24”. This is making mounting the wall plate challenging because I’m not sure where to screw the plate? Are there specific holes in the wall plate that I need to use (identified by arrows?) or can I use any of the holes on the mounting plate to attach it to the wall?

          2. We recommend that the mounting location has studs and can support the weight of the unit, and that the holes correspond to screw holes in the mounting plate. Please give us a call at 270-366-0457 so our tech team can best help you install this system according to your needs.

  83. I have a 3 car garage of 780 sq ft. Insulated 9 foot ceiling and Garage doors.I live in SW Florida and the unit will not be in direct sun. What size unit do I need?

  84. I have a 2 bedroom house of 1000 sq ft with vaulted ceilings of 12 ft in each room including the livingroom and kitchen. I’m in Vegas where it gets really hot for several months. The insulation isn’t that good either.

    My question is, would I be able to cool or heat my whole house with just one MR COOL of 21,000 btu’s pointed into the hallway and leaving the doors open? Or do I need individual units of lower btu’s in each room?

    1. While you could possibly do that, you may benefit more from a multi-zone DIY mini-split system, so you can make sure that every room in your house is covered. You can check https://mrcooldiy.com/ for more information as well as places to purchase.

  85. I’m building a 168 sq ft shed and will be insulting and sheet rocking the walls only. I live in Northern California. Will a 12k unit be large enough? I’m thinking it will be but would just like a second opinion

  86. My home was built in 1958. We’ve added insulation to attic and floors but walls do not have any. We have tung – n -groove interior walls with masonite exterior siding underneath vinyl siding. So, we not talking highly energy efficient. My house is all open on one side with about 550sq. (living, dining & kitchen). There are 3 bedrooms on the other side. What size unit would I need to heat/cool the open area?

  87. HI. I have a Summer cottage in Ohio. Temperatures that call for A/C range from 80-100 deg f. It’s mostly in direct sunlight with partial shade.
    It is approx 525 sf, with a vaulted ceiling, no insulation, and two tiny bedrooms off the main room. Would a 12k btu be too small and would an 18k be too big? Thanks

    1. A 12k might be too small, but an 18k should be sufficient for that space, especially since you mentioned that the cottage does not have insulation.

  88. I have a 28×36 ft garage with 10 ft ceilings. I live in northwestern Pennsylvania with winter temps averaging near 0 at night. Mostly concerned with keeping warm in winter, cooling in summer will be nice but not used as much. Could you tell me what size I would need ?

  89. I didn’t know that measuring your living space could help you determine what kind of air conditioner will best suit your needs. My brother wants to install an AC this summer. Hopefully, he can find one that will work well in his home.

  90. I have a wood shop approximately 805 SqFt with open ceiling to 13′ roof at the peak. Studs are 2×6 and foam insulated, as is the roof. Building is under shade. 99% of the time I will be the only one in the shop. Which unit would you recommend for efficient air flow circulation within the building? Building is rectangular.

  91. i am renovating my garage and mud room i have
    1 room 110 sqft ,bathroom 48 sqft , small office 72 sqft , office suite , 143 sqft and workshop of 313 sqft on the 5 split system smaller wall units that go into smaller rooms or are they all the same size

    1. The largest multi-zone that we offer goes up to four zones. The bathroom is likely too small for a single mini-split air handler, so if you install an air handler nearby and keep the door open when not in use, one would be sufficient. The smallest air handler that you can get in the multi-zone is a 9k BTU air handler, which normally covers around 250 square feet. If the spaces are more open, as well, or you could keep doors open for most of the time, you could get a larger air handler to cover the space. The air handlers that you can get with the mini splits can be 9k, 12k, 18k, or 24k BTUs in size. While 9k units cover 250 square feet, 12k units heat and cool 500 square feet. The 18k can cover 750 square feet, and the 24k can handle 1000 square feet. You can find more information about sizing at https://mrcooldiy.com/.

  92. Living in Phoenix, looking to cool a 690sqft garage w/ 9′ ceilings during the hot summers. No insulation on the ceiling, and 3 of 4 walls uninsulated. Different calculators show me anything between 14k BTU and 27kBTU! Target temp 79°. What size Mr. Cool mini split would you recommend?

    1. While an 18k unit may be able to cover you in a more temperate climate and in a space with better insulation, you may want to think about sizing up to a 24k, especially if you’re more interested in cooling. You can check https://mrcooldiy.com/ for more information.

  93. I am contemplating installing a minisplit ac system to my house. The total square footage is 1020. I have 8 foot ceilings with minimal (I think the ceilings have like R13 in them), and the walls which are cinderblock, currently have zero. The house faces south west with shade primarily on the east, south east side. The central living room is 15×24, with 2 bedrooms on the southern side of the home, and the kitchen & bath on the northern end, over a basement. I live in east Tennessee where summers can be hot and sticky. I am not sure how many btus I need, nor if a zone system might be preferred to a single central unit. Currently the main ac unit is a wall/window unit in the kitchen on the west facing wall, and its 24,000 btus. The unit does remove humidity, but it runs constantly when set at 72 degrees. Outside it may be 95 degrees. And with its placement, I need fans set up in the far end of the house to get any cooling down there. Would a 2 zone system; one zone being the kitchen, bath & laundry, and another for the living room and 2 bedrooms be a solution? If so, what size unit/s would I need?

    1. That configuration could be sufficient, if you think that works best for you. You would have to know the square footages of the areas you’re trying to cover to get the best possible unit for your needs, though. The air handlers that you can get with the DIY multi-zone mini splits can be 9k, 12k, 18k, or 24k BTUs in size. While 9k units cover 250 square feet, 12k units heat and cool 500 square feet. The 18k can cover 750 square feet, and the 24k can handle 1000 square feet. You can find more information about sizing at https://mrcooldiy.com/

  94. I have a 160 square foot detached cottage that I am converting to a home office. Currently through wall ac unit is to loud. Located in down state NY. Is your 12,000 btu unit the smallest you manufacture.? If so will this be to large and cycle on and off to rapidly thus actually not being efficient?

    1. The 12k BTU is the smallest DIY that we offer. It can normally heat and cool a space of around 500 square feet. While it may be oversized, the DIY can modulate performance well. Another option would be to go with a 9k unit from our Olympus or our Advantage series, but these are not DIY. They must be installed by an HVAC professional.

  95. I am looking at purchasing DIY 36,000 BTU 3-Ton 2-Zone Ductless Mini-Split Air Conditioner Heat Pump 230-Volt/60Hz. the first question is can you buy everything but the compressor if i wanted to add two more later or just go for the gusto? Next question. The front room and kitchen are pretty much the same room with an open floor plan. its 30’x20′ our bedroom where we plan to put the second one is 12’x14′. our house is roughly 1400 square foot. we have two bedrooms off the front room just down the hall. One id 8’x10′ and the other is 10×10. asking the experts what unit should i get? should i get 2 heads or 4 and do them all?

    1. While you can purchase the condenser and the air handlers separately, it would be the most convenient and the easiest to purchase them in a bundle all at once. The air handlers that you can get with the DIY multi-zone mini splits can be 9k, 12k, 18k, or 24k BTUs in size. While 9k units cover 250 square feet, 12k units heat and cool 500 square feet. The 18k can cover 750 square feet, and the 24k can handle 1000 square feet. For cooling and heating your bedrooms, you would likely have to get a 9k unit for every space. The 30’x20′ space can be covered by an 18k unit. While it would be more convenient to have everything you would need at the same time, getting just two or getting all four is ultimately up to you. If you decide to just get two, the added capacity of the two air handlers needs to meet at least half of the capacity of the condenser. You can take a look at https://mrcooldiy.com/ for more information.

      1. Thank you for the information. the other question I have is, can you run the lines through the attic? The drain would not go through the attic. Can you bend the lines coming from the air handler to go out the back of the handler and up through the wall and into the attic?

        1. That could work. We’ve had many customers perform similar installations successfully. If you have technical questions before or during your installation process, you can give us a call at 270-366-0457.

          1. One last question. If I install the DIY and I am not a certified contractor is everything still under warranty?

          2. You can perform every aspect of the DIY’s installation without the help of an HVAC professional and still enjoy the benefits of the warranty. You will still need a certified electrician to do electrical work.

          3. Ok we have decided on 3 units. 9K, 9K, and 18K. I will need a 16 foot line 50 foot line and 41foot line. Is it better to get a 50′ line or attach a 25′ and 16′ line? What size lines do I need?

          4. For a conventional mini-split, you should order lines as close to the lengths as you will need. The installing technician can modify them as necessary during the installation process. For one of our DIY units, the only available line lengths are 16′ and 25′. You would need a coupler kit to connect two 25′ lines together for a 50′ reach.

  96. Hi! I’m looking to cool my first floor. The floor consists of 4 different rooms, but there aren’t doors between the rooms, and most of the rooms have a significant opening to the next room. One room is 450 square feet, and the remaining three rooms are sort of connected like a railroad with no doors. THis railroad space is about 750-800 square feet. I’m torn between the 30000 BTU unit (12k +18k) and the 36000 BTU unit (12k + 24k). I live in central NJ and have 8 foot ceilings. What would you recommend?

    1. You might be able to get by with a 30k BTU unit with a 12k and 18k air handler. Really, you could do either, but since you mentioned that your home is more open-concept, the 30k unit should be sufficient.

  97. I live in one of the surrounding cities to Phoenix, AZ. The climate is very hot and dry in the desert. Gets over 100F in the summer easily. I want to cool my 408 sq ft 2 car garage. 3 walls and the roof are insulated. The last wall has the garage door where you can see sunlight coming in from some areas on the sides and bottoms. There is also two 1×1 vents to the outside for the gas water heater. I have seen estimates online from 11k to 19k btu unit. What unit size would Mr Cool recommend?

    1. While we cannot provide an exact size, an 18k BTU unit would not seem out of the question given the information provided.

  98. What size of AC do I need to cool a woodworking shop 20 x 32 x8. I have in-floor heating, so heat is not wanted. Good insulation in building with 4 windows at 4’4″‘ x 2’9″. Two windows on the sunny South side and 2 on the East side. Unit will be placed on the East wall and compressor set on the east side of building. Please comment about the dust that a hobby woodworking shop produces and it’s affect on Mr Cool as I am concerned that daily cleaning of the filters may not be enough and efficiency and operation will be adversely affected.

    1. For that space, an 18k might be sufficient. Operation would only be adversely affected if the unit’s airflow was impacted, which should not be a huge issue if you are prepared to clean the filters often and check the air inlet relatively often. The DIY has been installed by many customers in many similar applications successfully.

  99. I have a 30×40 (~1200sqft) detached garage with 8.5 ft ceilings. I’m afraid the 24k btu unit is too small and the 36k btu unit is too large for that space. Additionally, I already have 10 gauge wire run, which isn’t rated for the 40 amps required for the larger unit. Would I be able to get by with the smaller unit or better off running new electrical and buying the larger unit?

    Located in Ohio with good insulation except for two garage doors which are ok insulation but don’t seal tightly.

    1. Since you mentioned that you have relatively good insulation, you might be able to get by with the 24k, but you would definitely get the best results and the greatest overall comfort from a 36k unit.

  100. I like that you pointed out that having a professional will be able to assess the right size to cool the area or space we want to put the system in. It really is the best idea to do so rather than guessing on our own. I will tell this to my husband so that we can start looking for an expert tomorrow since we need the system installed as soon as possible. It’s for our new home which we will move into in a couple of weeks from now.

  101. I want to heat/cool 3 rooms, a basement with 2 rooms and a garage, The 2 basement rooms are 750sf and 200 sf, the garage is 400 sf with 14’ceiling, Can i have different air handlers for each room? and if so what size btu unit would I need?

    1. You can have different air handlers for each room! If that’s what you want, you might be able to get by with a 36′ BTU condenser that has a 9k air handler (for the 200 square foot space), a 12k air handler (for the 400 square foot space), and an 18k air handler (for the 750 square foot space) depending on different factors, such as the climate you live in and your home’s insulation levels. You can take a look at https://mrcooldiy.com/ for more information.

  102. The part of your article that talked about things like cold or hot spots as a reason to get a bigger unit was really helpful. Some parts of our house, specifically the kitchen, never get enough cooling for those days that we really need it when the heat becomes unbearable, and I wondered how we could fix that. I’ll take your advice and look for any HVAC contractors that can help us find out what unit best suits our house so every room can be cooled evenly.

  103. I moved to a small one bedroom apartment,,with a new mrcool ac/heat unit, but my bil is about $400.00 every month, WHY??

    1. A high electricity bill can have a number of causes. A high efficiency unit can still generate a high bill if operating in a poorly insulated space with a large divergence between the setpoint temperature and the outside temperature.

  104. Hello, I’m debating between the 23k unit and the 36k unit to put in my wood shop. I have roughly 1200 sqft with 10’ ceilings on the side and a high center ceiling (was built for an RV), the walls are pretty well insulated and I have sheeting up throughout. I also live in a temperate area so have the occasional extreme temps, in the summer time it’s mostly the humidity I’m battling. I was wondering if you would recommend one unit over the other in my case. I want to get get what makes the most sense as I’m not out here 24/7 but want to be able to keep it comfortable without killing my electric bill.

    1. While we couldn’t say for sure without a Manual J load calculation, it sounds like the 36k could be a better fit.

  105. I live in Houston TX. Need to cool a 3 car garage 32x22x9. Finished garage with no insulation on walls or on the 3 aluminum garage doors. No shade, garage gets afternoon sun and heats up.
    Which 3rd generation unit do you suggest?

    1. Typically, the 18k unit can cover around 750 square feet, but in the conditions you’ll be operating your unit in, you may want to consider the 24k BTU unit. You may also want to consider insulating your garage. For more information, check out https://mrcooldiy.com/.

  106. What if I have a brick wall and windows and no were to drill a hole ? I need heating and cooling for a four season sunroom.

    1. It is possible to drill through brick. You can route the line set through the side of the air handler since there are knockouts. For the best advice regarding this installation, please give us a call at 270-366-0457.

  107. I’m putting a unit in my garage for a home gym. The garage is insulated walls, doors, and ceiling. 660 square ft and 9.5ft ceilings. Debating between a 18k or 24k. My concern with 18k is that it’ll take too long for the air to go back to the correct temp when a garage door is opened to pull a car in/out. What do you think?

    1. While that is a realistic concern, a 24k may be too oversized, which could potentially cause issues in the long run. Depending on climate and other factors, an 18k would likely be sufficient.

  108. My existing heat pump is 3.5 tons and I’m interested in the universal heat pump. But the models are 2-3 tons and 4-5 tons which unit should I purchase?

  109. I have purchased a 12k for my insulated 2 car garage. It is still on its way to my house. The garage is 418sqft with a 10ft ceiling. Two exterior walls. The other two are shared with other conditioned rooms of my house. The garage door gets direct evening sun for a few hours. I live in southern Kentucky so I see harsh temps both hot and cold at times. I was hoping to have my garage at or near 70* year round.

    Is the 12k going to be enough or should I cancel the order and opt for the 18k instead?

    1. The 12k BTU unit will likely be enough. It can normally cover around 500 square feet, so in these conditions, your system should operate fine.

  110. Looking for the right size. 2 car garage (barely), no insulated walls on 2 sides (drywalled but no insulation), regular metal garage door with no insulation. 462 sqft, 9 ft ceilings. Hot humid climate. Looking at the 18K but not sure if I should go the 24K or if that’s just too much.

    1. The 18k should work fine. It can typically heat and cool areas of 750 square feet, so in an uninsulated garage, it should work appropriately.

  111. I live in Fort Mohave Arizona and looking to buy a Mr cool mini split for my garage. The garage is about 600 sqft with double aluminum garage door, that I insulated. The walls and ceiling are dry wall with no insulation and regular height.
    Your thoughts on a 18k Olympus dual zone unit?

    1. With no insulation in the desert, I would consider installing a larger unit. Also, you probably don’t need a dual zone, unless the garage is partitioned with a dividing wall.

        1. We might recommend a 24k BTU DIY ductless mini-split system, or a 24k BTU Olympus system, depending on whether or not you want to install the unit yourself. A 24k unit can typically cover around 1,000 square feet, so it should work for an uninsulated building in your climate.

    1. Each air handler and each condenser will have its own BTU rating. Ideally, a split system should have an air handler and condenser that handle the same amount of BTUs.

  112. I want to use a Mr Cool to heat/cool the second floor of a metal building. How long are the lines that go from the outside unit to the room units?

    1. While the single pre-charged line sets for the DIY ductless mini-split are offered in increments of 16′ and 25′, you can link two pre-charged line sets together using a Quick Connect coupler kit so that you can create the length you need.

    1. It depends on a number of factors besides square footage, such as climate, insulation, sun exposure, and a number of other things, but in your case, a 36k BTU DIY ductless mini-split could be sufficient. Take a look at https://mrcooldiy.com/ for more information and retailers!

  113. I have a 450 sqft garge that is insulated it has 2 large windows and a 8ft sliding glass door. The ceilings are 14ft tall. What size unit do you recommend?

    1. While you’ll want to take climate and sun exposure into consideration, we might recommend an 18k BTU mini-split, because of the windows and the high ceilings.

  114. 600 sq ft bedroom (yup), direct Hawai’i sun all blooming day long, zero shade, 4 large windows and double sliding door (a lot of glass), no insulation anywhere. On the plus side, the ac will go on the northern, much less sunny side. Help me I’m melting.

  115. I have a guest house in south Carolina,400 sq ft.R 13 in walls r 19 ceiling.windows all 4 sides.which do you recommend 12k or 18 k.

    1. A 12k BTU DIY mini-split typically covers around 500 square feet. It might depend on sun exposure, the height of the ceilings, the number of people typically in the room, and a variety of other factors, but a 12k could be suitable.

  116. I have a room that contains scientific instruments that put off heat. The room is 15×12 with 8 ft ceilings. Right now it is 52 degrees outside, and the room is 85 f.
    What size unit would you recommend?

    1. Our smallest DIY ductless mini-split system, which is a 12k BTU unit that typically covers around 500 square feet, may be slightly oversized for that space. You may want to consider a 9k BTU Olympus system. A 9k system typically heats and cools around 350 square feet, which is still slightly oversized, but since you have the instruments that produce heat, it should be fine. The Olympus is not a DIY system, though, so it must be installed by an HVAC professional. You can find these units anywhere our units are sold.

  117. I have a 17 x 25 foot (425 sq ft) room in need of a Mr. Cool. I live in Maryland
    My challenge, the room has 3 exposed walls with 2 sliding doors and a number of large plate glass windows (~150 sq ft or windows)
    Trying to decide between the 12K or 18K ?
    Any advice would be appreciated.

    1. The 12k can typically heat and cool a room of 500 square feet, but you may want to consider the 18k because of factors such as 3 exposed walls and multiple windows.

        1. The DIY does well in scenarios like this, and it can be set on a lower mode of operation. The 12k will likely be undersized with the different factors affecting the room that you describe. If you’d like, you can give us a call at 270-366-0457.

          1. How can the unit “be set on a lower mode of operation.”? I have the smallest DIY unit, 12k, in a 120 sq ft detached office shed. I find it gets a bit too humid. How can I lower its power so it dries it out more?

  118. I’m finishing out a 16×48 (768sqft) cabin with great insulation (R28 walls, R27 roof and R27 floors). Will have one door and about a dozen windows. Do you think two 9k units would suffice in Oklahoma (Humid, 110 deg highs, 5 deg lows). Thanks!

    1. A 9k unit can typically cover around 350 square feet. While we do not have a single-zone 9k DIY ductless mini-split, you could get a dual-zone DIY ductless mini-split with two 9k air handlers. Because you mention that you have multiple windows in this space, you might also be able to appropriately use a dual zone system with two 12k air handlers, or two single-zone 12k BTU DIY systems. Ultimately, it is up to you and what best fits your needs. For more information on our DIY ductless mini-splits, including helpful sizing guides and places to purchase, please take a look at https://mrcooldiy.com/.

  119. Hello. I have a newly constructed workshop 53×28 with 13’ ceilings. Heavily insulated, two windows north facing. Already pre-wired with two disconnects (just in case:)
    I am in west central Oregon (Roseburg) , so it does not get too cold or too hot.
    What size unit(s) do you recommend for occasional use?

    1. You may be interested in a 36k BTU DIY ductless mini-split. This system can typically cover spaces around 1,500 square feet, and since your space is well insulated and located in a more temperate climate, it may work for you.

  120. I have an approx. 700 sq foot open living/dining room/kitchen mostly rectangular space. 9ft ceilings, an entire wall of 100 yr old single pane windows, and it seems no insulation in the walls. Located in Southern California, but closer to the beach, so don’t see the most extreme heats in summer, though inside of the house hit 50f the last few nights this winter.

    I’m contemplating between 1 x 24k unit in the middle vs. 2 x 12k units (one at each end of the space). What would you recommend? Thanks

    1. Either one would work well! A single 24k unit would only require the installation of a single air handler, while the two 12k units would be a slightly more complicated installation. The two 12ks would offer individual control of each unit, which may be preferable depending on your wants, but if you only want to deal with a single unit, then the 24k would be more convenient. All of this to say, there are pros and cons to choosing either unit!

  121. I just bought a 800 square foot double manufactured home in winter haven florida. The 3 ton ac unit just went out. I know this unit was tooooo big. I am looking for a new ac and furnace together. Looking to buy from Lowe’s. What would be the approximate cost to replace this.

    1. We don’t offer estimates because we don’t sell direct. If you’re interested in a system like the Universal central heat pump split system, please take a look at https://mrcooluniversal.com/. This site will direct you to more information such as pricing, sizing, and places to purchase.

  122. I live in northern Nevada and have a detached shop that is 1600sqft and is 2 stories 800sqft each floor. Bottom floor has three 10ft uninsulated garage doors and 8ft ceiling. Upstairs has vaulted ceilings at 12ft. The building is insulated other than the garage doors. Temps are mid 90sF in the summer and average 20F in the winter. I was looking at a dual zone 36k with two 18k units. Would this be adequate to keep the building at 65F in the winter and 85F in the summer?

    1. That could potentially work for you, but we would recommend insulating the garage doors if at all possible. Depending on your climate, this system may actually be slightly undersized. While a 36k condenser with two 18k air handlers may work for you, a 24k BTU system and an 18k BTU system, or two 24k systems might work better.

  123. Hello,
    What DIY unit would you recommend for my 3-1/2 car garage in Southwest Florida (Naples).
    It is about 750 sqft 21’ x 37’ with 8.5’ ceilings. It is insulated with one 36” x 60” window on the north 21’ wall. I will need to place the unit on the south 21’ wall . I do use a part of the garage as a workout area which can be tough in the summer as the garage will reach 91-93 degrees during the day and mid 80’s at night
    Any guidance will be very much appreciated.
    Thank you.

    1. While an 18k can typically handle spaces around 750 square feet, you might want to consider a larger unit, like a 24k BTU system since you live in a warmer climate.

  124. Hello,
    I am looking to install a DIY system in the upper unit of one of my older duplexes in Milwaukee, Wl and was hoping to get some help with sizing. It is a long narrow space and while its only ~620 square feet, I’m wondering what size you would recommend with all the walls (2 bedroom w living room, kitchen, etc.)? There is just a long narrow hallway connecting all the rooms so I’m concerned with how 1 unit would be able to balance out the space, especially with people in the bedrooms with the door closed. Reading the comment above, it sounds like one 18K would be enough for the square footage, but not sure if it would reach from end to end (40 ft long) or if it would be best to go to a 2 zone. If so, what individual size of each unit/condenser combination would be recommended to avoid the short cycling described above?

    1. If you’re wanting to heat and cool separate spaces, you might be interested in a multi-zone. We do have DIY multi-zone mini-splits that can support up to four air handlers per condenser. If you still want to go with just a single zone, an 18k would be able to handle that space. Our smallest DIY ductless mini-split is a 12k BTU system, which can normally handle spaces around 500 square feet. Two of these with one placed on either end would likely be too much. If you’re wanting a 2 zone to handle the hallway, there is a configuration that has two 9k air handlers, which would be much better suited for this space. Check out https://mrcooldiy.com/ for more information!

      1. Thank you for the reply! You mentioned two 12Ks would likely be too much, so currently I am looking into the 21,000 BTU 2 zone split unit with the 9k and 12K Wall Mounts combination from Home Depot, with the 12K in the living room/hallway and the ok on the other end in the bedroom:
        DIYM227HPW01 B05/314882879
        Just want to verify you don’t think it wouldn’t be too oversized to avoid the short cycling! Also the line lengths would have to be 50 and 75 ft, not sure if this affects the sizing?
        Thank you again for the support!

  125. I have a detached office with full bath that comes out to 370 sqft with 8 foot ceilings in Southern Louisiana. I have seen 12k btu suggested by your calculators but I am confused why it wouldn’t be 9k. As well, wouldn’t the 12k be overpowered for the space and short cycle?

    1. We typically size 9k BTU units to cover spaces under 350 square feet. Depending on a number of factors, including climate, sun exposure, insulation, and a number of other variables, the unit that we recommend may change. The risk of short cycling with these units is low, unless the unit is extremely oversized. The smallest DIY ductless mini-split that we offer is also a 12k BTU unit. The single zone 9k units in our other series must be installed by an HVAC professional.

  126. Hello,

    I have a 900 sq ft finished walkout basement. Two windows and a French door, Only need minor cooling in the summer but need heat in the winter. Live in Massachusetts, do you recommend the 18,000 or 23,000? Thanks

  127. I have a 14×45 insulated steel building with insulated garage doors. Floor to peak is 14Ft. What size mini split would I need for heat and a/c

  128. I live in Central Ohio. I’m just finished out my 390 sq ft garage and turned it into another room with a big 9 ft long window. I have fully insulated the room/ceiling. The ceiling is also 9′ in height. It can get very humid and in the mid 90’s during the summers, and can get well below freezing in the winters. What size would you recommend?

  129. Hi Mr. Cool! We want to put a mini-split in a ~1,000 sq ft area that includes is an open floor plan with a kitchen and great room with a two-story ceiling (16 foot) and floor-to-ceiling windows that face West. The home is in the White Mountains of NH where the highest average temp is 81 in July. There are existing ceiling fans in the great room, if that makes a difference. Also we are primarily interested in the A/C, not heat. What size do you think we need? Will 18,000 do it or do we need more? Thanks so much!

    1. The 18k BTU DIY ductless mini-split typically covers around 750 square feet. We would normally recommend at least a 24k BTU system for 1,000 square feet, but since your ceilings are so tall, you have tall windows, and you need for your system to cover a kitchen, which can get very hot very fast, we might recommend a 36k BTU system. You can find more sizing information, and information such as pricing and places to purchase, at https://mrcooldiy.com/.

  130. We are building a 900sq’ home that we would like to install a mini split in. There will be one 170sq’ bedroom, one 120sq’ bedroom. The rest of the home is very a wide open space with 12′ ceilings. What would you recommend for a kit?

    Thank you

    1. You might be able to use a 3 zone DIY ductless mini-split with a 9k air handler for each bedroom and one 18k air handler for the rest of the space. Check out more information, including pricing, sizing, and places to purchase, at https://mrcooldiy.com/.

  131. My house is a simple rectangle with 1100 sq. ft. on the main floor. The kitchen, dining room and living room are all in an east-west line in an open area of 600 sq. ft. facing south with lots of windows. The master bedroom is 175 sq. ft. on the other side of the living room north wall and has a 4ft. x 6ft. window facing north. The door to the bedroom is off a 6ft. wide hallway leading from the living room to the front door. Ceilings are 8ft. and the attic above is vented and has moderate insulation. What would be the optimal arrangement and size of a mini split system to cool both the open area and master bedroom? I am not as concerned about the study and bathroom. Could it be done with a single zone unit in the living room room. I live in Vancouver, BC. What size would be needed to just cool the bedroom.

    1. You could potentially use a multi-zone DIY ductless mini-split with a 9k air handler for the bedroom and an 18k unit for the 600 square foot space. If you want a single zone unit to cover the entire house, you might be interested in a 36k BTU unit, which can cover spaces up to 1500 square feet. You would simply leave the doors in your house open when the rooms are not in use to cover the entire space. For more information, including info regarding sizing, pricing, and places to purchase, check out https://mrcooldiy.com/.

  132. Needing some advice. Have a small 14×50 (700 sq ft) shed-to-home w/single slope 8′ – 12′ roof. Main Kitchen/LR is 303 sq ft avg ceiling ht. 10′. Master BR is 132 sq ft avg ceiling ht 10′. 2nd BR is 82 sq ft. avg ceiling ht. 9′. Bath is 65 sq ft. avg ceiling ht 9′ only other space is Hallway 3.5′ x 15.75′ avg ceiling ht 11′ that connects the bedrooms and bath. This is 6,500′ elevation “summer use” only in “Zone 5 so temps rarely get into the 90’s but can get into the 30’s at night. It is insulated with closed cell spray foam and has avg. amt of windows.

    I know I need multiple zone but debating between 2 or 3 heads. Would like prefer 2 zone with one unit in the 303 sq ft main living area and 2nd head in the hallway and let it feed the two bedrooms and bath 334 sq ft combined. Would that work? Or do I need a head in each bedroom? If “2 heads” what size units would you suggest? If “3” what size? Thanks in advance.

    1. Whether or not you want an air handler in the bedrooms is up to you. Our smallest air handler size is a 9k BTU unit, which can cover spaces up to 350 square feet. Depending on insulation, climate, sun exposure, and other factors, you could possibly cover the main space with a 9k air handler, then install either a 9k air handler in each bedroom or one 9k air handler in the bathroom to cover the bedrooms and the bathroom. We would not recommend installing an air handler in the bathroom.

  133. I’m interested in the Mr. Cool DIY 36k unit and am struggling with confirming head sizes for my Seattle, WA, 1920’s era home (moderate sun/insulation/windows assumptions). Room sizes are: upstairs separated 1bed apt at 612SF, main floor living/dining at 597SF, and two main floor bedrooms at 156SF each. I’m thinking a head configuration of – 18k (upstairs apt), 12k (main living/dining), 9k (bedroom 1) and 9k (bedroom 2) may work okay.. but I’m wondering if the 9k heads may be oversized for the bedrooms and if the 12k may be undersized for the main living/dining area? Is it reasonable to assume that if the 12k unit is slightly undersized that it will be supplemented by the 9k bedroom units, assuming doors are left open during the day? Thanks

    1. The two 9k air handlers will definitely be able to supplement the space that you’re looking to install the 12k in if you leave the doors open during the day. It seems that if you were to use your system as you describe, it should be alright. If you’d like, you can give u a call at 270-366-0457 for more information.

  134. 1100 square feet house 3 bedrooms and living room thinking 4 zone unit 9000btu handler in bedrooms and 1200 btu handler in living room approximately 36 btu because I have a flat roof and decent insulation and live in hot climate would that be a correct sizing for my house?

  135. Looking to purchase a 12k mini to install in a insulated shed that is 110 square with 9 feet high ceilings. The unit is rated for 500 Sq feet. Can you run the unit in a room of this size with out humidity issue. Live in a warm arid climate

    1. It may be a little large for that space, but as it is our smallest DIY unit, it could work, especially turned to a lower mode of operation. We do have 9k BTU units in our Olympus and Advantage series, but these are not DIY and must be installed by an HVAC professional.

  136. What size unit would I need? I live in the north east and just finished a 440sqft room in the basement. It has windows and insulated. The basement is 1/2 under ground. I will be using it for heating and cooling the room.

  137. The only exterior non-street facing wall on a corner lot is the small master bathroom attached to a 10×12 master bedroom.

    Considering the 12k Gen3 DIY inverter model can throttle down to about 5k, can it potentially work being mounted in the master bath, which blows directly into the bedroom?

    Any plans to eventually make a tiny ~30 SEER 9k DIY or a small two bedroom multi 6k + 6k (12k outdoor unit) with option for very short 5’ line sets?

    How much is Seer improved if one could use a 5’ line set versus the stock 25’ line set on a 12k DIY Gen3 unit? Are there after market splitters to allow a single zone outdoor unit to be converted to dual zone output (with a properly train A/C tech to install).


    1. The 12k BTU may be able to do that, although we don’t like to recommend that a system be installed in a bathroom or a similar high-humidity environment, as it could negatively affect the performance of the system over time. We do not currently have any plans to make that small of a unit, and many times, line sets must meet a certain length in order for the unit to properly work. SEER should not be affected by the length of the available line sets. We do not sell such a product, and we cannot recommend their use, as it would likely void the warranty.

  138. i have a shop 24’x30′ with 12′ walls all the walls have r19 insulation has no windows and all insulated doors the building is all metal and in 80% in the sun. What size btu ac mini split would be recommended

    1. Depending on the climate, we might recommend a 24k BTU DIY ductless mini-split system, since your ceilings are tall and your shop is in the sun.

  139. I have a 30×40 metal building with 12’ wall height, located in central Indiana. The building has 2” of closed cell spray foam on the walls and ceiling and one insulated overhead door. What size DIY unit would you recommend for a spray foamed application? Would a DIY unit efficiently heat to 55F during the winter? Winters typically reach low teens, a few days of zero or below.

  140. Q1- My return comes in from the top. Deal breaker?
    Q2-I have a 2080sqft home with 10ft ceilings in western Montana, zone 5b. Its ducted and I need a dual unit. 2/3 or 4/5 ton?

    1. The Universal is upflow/horizontal airflow, but the condenser can be used with a downflow air handler of another brand if necessary. We would suggest a 5 ton system for this space.

  141. Looking to build a 16×24 2 story home 768 square feet. I was thinking 18k with 2 9k indoor units. Do you think this would be sufficient for East Tennessee ( Gatlinburg) area?

  142. there isn’t a clear direction on how to factor in ceiling height. I’m looking at the 4th gen DIY single zone.

    my garage is exposed to the sun on 2.5 sides, insulated on all sides, with no windows, and only 2 garage doors (insulated). It is mad hot in the summer, and super cold in the winter. The garage measures 20×20 for a 400sq ft. the calculator says 12k.

    With 9.5 ft ceilings is the 12k BTU unit sufficient or should I step up to the 18k?


  143. I’m looking to convert my home cooling needs to run on solar here in south alabama. I have a 5K system installed and able to produce 240Volts at 25 amps. What is your electrical requirements for the 4th. Gen. 27K Three room system 9K/9K/12K.

  144. Hi My home has these rooms. Bedroom 1: 175 sq ft, Bed room2: 160 sq ft. Bed room 3: 105 sq.ft. Living and kitchen combined is 510 sq ft. I understand 12k BTU indoor unit will work fine in the living/kitchen area, but Is 9k BTU unit too big for bed rooms ? Appreciate you guidance.

    1. A 9k BTU air handler could work well for these spaces, especially if their doors are open to ensure the air is spread to other portions of the house.

    1. It may depend on what you’re looking for! If you want to heat and cool your space with DIY mini-splits, you might need more than one system, or a DIY 5 zone system! Sizing with mini-splits depends on the square footage of spaces you’d want to install an air handler in, which might include bedrooms. If you want a central unit, a 3 or 3.5 ton unit might work well for you. All in all, sizing is also greatly dependent on factors like climate, sun exposure, insulation quality, and other variables.

    I live in a 13 x 45 ft long trailer in NorCal (500+- SF of interior living space). Have already decided to purchase MRCOOL, so only remaining decision is one single unit or 2 multi-zone system. Living/Kithen has no wall separation – one large space 25.6 x 13 (162.5 SF) which appears to translate to 3250 BTU. Then, Kitchen leads to 11 x 6.2 ft long hall way to bath and bedroom which is 11.4 x 11 (126.5 SF). so total SF from hall thru bedroom is 248.5 or 4970 BTU. End to end clear view from one end of living room to back wall of bedroom when bedroom door is open (all the time).
    Will one unit heat/cool the entire trailer or multi-zone units, one at each end of trailer? Can you link me to either option so I can read up on them? I would also appreciate your professional opinion on best option with this config, please. Order direct or who is my dealer in Brentwood CA? Do plan to DIY using a handyman who is pretty good at electrical. Or any MRCOOL installers in my area?

    1. You would need to leave the doors to the spaces that you want to keep cooled or heated open so that they are appropriately covered. This space seems slightly oversized for a 12k, so you may want to consider an 18k, which would be good if your space is not well insulated or if it gets a lot of sun exposure. If sized well, one unit should be able to keep the space comfortable, but using a multi-zone unit with one on either side may initially spread airflow a bit better. You’ll find info on the single-zone system at https://mrcool.com/diy-4th-generation/, and info on the multi-zone system at https://mrcool.com/diy-4th-generation-multi-zone/. You’ll be able to find our online dealers at https://mrcooldiy.com/, or if you prefer to buy locally you may be able to find a dealer near you at https://mrcool.com/where-to-purchase/. You can find our installers at https://mrcool.com/installer-map/!

  146. Have two situations I need to size:

    1) 120 sq ft shed on concrete slab, the ceiling is standard height at about 8 ft, there appears to be no insulation in the walls, and I don’t remember seeing any insulation in the rafters before we put the ceiling in. This will be a workshop with some storage. Even tho it gets hot and very dry here in Sacramento, CA, there still seems to be quite a bit of humidity (50-60%) in the shed. So is the smallest Mr Cool unit (12K BTU) going to be too big, and will a mini split help me with that humidity? I’d like the shed to be more pleasant to be in for both me and the contents.

    2) Two upstairs bedrooms in our house get quite warm in the summer. The worst is the master bedroom with vaulted ceiling in the SW corner of the house. With floor evap cooler and old undersized AC, we can pull the bedroom temperature down after several hours, but then downstairs has to be kept cold all night. So we were thinking of installing a 12K BTU for each bedroom, or a larger 2 head unit. Which do you think would be better? Master bedroom is about 10×15’ with a 10’ vaulted ceiling,and smaller bedroom is about 10×10’ with standard ceiling height. Sealing up in the attic plus much better insulation up there is also req.

    1. 1) A mini-split will help with the humidity. Since there is not insulation, a 12k will be large but not greatly oversized. You can also always operate it on a lower setting. A 9k Olympus or Advantage is also an option, but these are not DIY and require an HVAC professional to install.

      2) It’s mostly about what you want! You may want to consider one of our most recent systems, which is an 18k dual-zone DIY condenser with two 9k BTU air handlers. These may be a better fit for these spaces with regards to size.

  147. Hi I have a 30′ 30′ x 12′ ceiling garage with spray foam insulation on all sides, it faces east/west with insulated garage doors facing West. I live in South Texas near the coast (Rockport). What size mini split btu unit will fit my situation best?

    1. Because your garage has pretty tall ceilings and you live in a warmer area, I might recommend the 36k BTU instead of the 24k. The 36k can handle around 1,500 square feet, and the 24k is normally equipped to handle 1,000 square feet.

  148. I’m looking at a mini-split system to cool my workshop which is in the drive under garage of my home. It will be climate controlled only when in use, not constantly.

    It is 50’ x 51’ There are (2) insulated garage doors measuring 8’x18’ and (9) double pane windows measuring 3’x5’. Half of the house is completely covered by trees, and the whole first story will be open cell foam insulation in the walls and ceiling.

    Thoughts on which mini-split would be best?

    1. Unfortunately, we do not have a single-zone mini-split system that is large enough to deal with this space. Our largest single-zone DIY ductless mini-split system is a 36k BTU DIY ductless mini-split, which can normally handle around 1,500 square feet. You could possibly put two of these 36k’s in your space, or, since it sounds like your space is well-insulated, a 36k and a 24k, in your garage. It really depends on what you need.

  149. I have a 30×60 hanger with a 12′ ceiling. It is well insulated. The hanger is in Mountain Home Idaho which is SE of Boise. Which DIY system do you recommend? Also. should I install the heads on the short wall or the long wall?

    1. We might recommend two 24k BTU DIY ductless mini-splits to handle this system. You could also use a 48k BTU multi-zone system with two 24k air handlers to cover this space! Either wall should be fine, as long as the air handlers are placed in an open location where they can cover the space you need.

  150. I am looking to install a 12k DIY in a kitchen that is 140 Square feet – it is a tight space, but it can get relatively hot in there when the burners or oven are going, or the sun is coming in directly through the windows. I think given the small size of the space a 12K would be sufficient, just wanted to get another opinion.

    1. While it may be slightly oversized for this space, if the kitchen leads to other spaces in the house, and the space already gets extremely hot as you stated, it should be fine.

  151. Looking to purchase a unit. I have a 3 bedroom solitaire mobile home 1700 sq. ft.
    What unit should I be looking to by?

    1. You may be interested in one of our multi-zone units! Depending on a number of factors, we might recommend a 48k BTU condenser. The air handlers you get depend on the size of the rooms you want to install air handlers in.

  152. Installing a wall-mounted built-in air conditioner instead of a window air conditioner is actually more efficient and can do a better cooling job. If you think about it, a window unit likely sits low in the room.

    1. You would likely need multiple systems. It may depend on if you’re heating and cooling separate spaces. It also depends on whether or not your space is insulated, what climate you live in, how much sun exposure the space gets, and a number of other factors. It seems that possibly two 24k DIY ductless mini-split systems and a 12k DIY system could work for you, though.

  153. I have a small shed I am turning into a cabin (about 150 sqft). Metal roof, T1-11 siding, R13 in walls and ceiling, 3 single-pane windows, ceiling max ~9′ at peak but barn-style roof and 2 lofts at 6’6″. In sun most of the day. Located in Arkansas (hot and humid summers).
    I am leaning towards a DIY 12K unit. Would that be too much for such a small space?
    Would I experience short cycling or lack of dehumidification?

  154. Hello,
    I live in Michigan (lower peninsula) and am interested in going with a mini split. It is a 100 year old two story home that is approximately 1400 sq ft. Main floor has the living room, dining room, kitchen, bathroom, and master while the second floor has the stairway area that is open along with 3 bedrooms. I would split sq ft as 700/700. I was thinking about placing a mini split in the living room and one in the room area that is open where the stairway is on second floor. I am torn between the 2 zone or 3 zone. If I were to go 3, I would place a small one (9k) in the master bedroom on first floor. Do you think this is sufficient? My thoughts were the (9+12+18) 36k unit, using 18k for main, 12k in second, and 9k for master. Thank you

    1. It would depend on the square footage of each space that you want to put an air handler in. While we do have systems with that air handler configuration, you would want to ensure it would work for your house. The 9k air handler is typically equipped to handle spaces up to and around 350 square feet depending on climate, insulation, sun exposure, and a number of other factors. The 12k can normally cover around 500 square feet, and the 18k can handle around 750 square feet. If this works for your spaces, it might be a good fit for you!

  155. Pensacola Florida temperature 20 to 105f – 400sqft garage with 8.5ft ceiling, insulated on 3 sides the garage door is not insulated. Room will be used as workshop & gym. Considering 18k or 12k mr cool 4th gen. Been leaning towards the 18k. Now worried it may be too much. Can you please advise me on what you think is best. Thanks

  156. Kansas City, KS, 680 sq. Ft., 10’ ceiling, 3-car garage, insulated on 2 side walls and half of the ceiling, exposed on north side, insulated garage doors. Garage will be used intermittently for vehicle repairs. Looking for heating and cooling sizing recommendations for a single zone mini split.

    1. Since the ceilings are so tall, it may be too large of a space for the 12k. We might recommend the 18k, especially if this space gets a decent amount of sun exposure.

  157. 1600sqft block building on a slab with older insulation in attic and barely any on walls. Has an old oil furnace with ducts already. Planning on removing furnace and utilizing duct work and vents for Mr Cool DIY universal split system. What size? 2-3 or 4-5 ton?

    1. The only way to know what size system you need is to have an HVAC professional perform a Manual J load calculation on your space. We can only estimate the system that you need. Based on what you have said about your space, we might recommend the 4-5 ton Universal on the 4 ton setting, but we would also suggest hiring an HVAC professional to verify this.

  158. I have a 2000 sq/ft home in SW Virginia (zip 24381) and have a 3.5 ton split 10 seer unit now that is dead. Would you recommend a 3 ton or 4 ton unit? Thanks

  159. I have a house with 900 sq feet main floor. Two bedrooms that are sub 154 SQ ft each. If I put a 9000 but air handler in each room, will they not short cycle due to being oversized? I have seen in other posts the recommendation of leaving the doors open. With these being bedrooms, the doors will be closed at night. Please advise on short cycle concerns

    1. Hi Jeff,

      The units would be pretty oversized for both bedrooms, but it should be alright if turned to a lower fan speed/mode of operation overnight. Is there any way that ventilation can be added to the room? If not, no worries, the lower mode of operation should be fine for a limited period of time.

  160. I have a two story 2,400 sq ft built in 2000 house in NW oregon . I have a heat pump now was looking at replacing it with a mr cool central unit using my existing furnace. What unit would you recommend going with .

    1. A number of factors go into deciding on the size of an HVAC system. The best course of action would be to have an HVAC professional perform a Manual J load calculation on your home to see what size unit you need. Another solution is to go with the size of your current heat pump if you know the size of your heat pump and it heats and cools your home effectively.

  161. I have three bedrooms that are sub 140 square feet each. Assuming that these bedrooms would be closed for 8 hours a day and not able to get air from another air handler each room would need its own air handler. The smallest air handler that you offer is 9000 btu. According to what I’ve read this is too big for this small of a room and will lead to short cycling. Will this actually lead to short cycling or will your unit work on a room that is this small without short cycling?

    1. Short cycling can happen to any HVAC system if sized incorrectly. However, if the air handler is installed in this space and kept on a low fan speed, it may work well for the space. Sizing can also depend on a number of factors, like climate, insulation, and sun exposure.

  162. I’m looking for an AC system for my shop. It is a 30×40 building with 12 foot walls, Well insulated. Located in Central North Dakota. Beings that it has 2 large overhead doors that will be used I’d need something large enough that it can recover from large cool air losses from the doors opening and closing.

    1. It seems that you might want to look into something like our 36k BTU DIY Ductless Mini-Split. This system has a TURBO mode, which would help get your space to the temperature you want faster after air loss from the doors opening.

  163. Hello. What options BTU wise do I have for a cooling/heating a new metal building that measures 45 feet by 24 feet with a 14 foot ceiling here in DFW, Texas. It has a large 12 feet by 12 feet garage rolling door. It is insulated with 2.5 inches of closed cell spray on insullation. It will be used to work on cars. I believe I would need 2 heads to assist with airflow. Thanks

    1. We would likely recommend a single 36k BTU DIY Ductless Mini-Split, or a 36k BTU DIY Multi-Zone condenser with air handlers to match the BTU capacity you need in the specific zones. If you want to split the dual-zone capacities evenly, we’d recommend two 18k air handlers for the 36k BTU condenser. To find a dealer near you, check out our Where to Purchase page! For more information on the DIY, take a look at https://mrcooldiy.com/.

  164. Hi,
    I have an 20 yr old Trane 60btu furnace coupled with a Braynt 2.5 ton Electric AC. I have a colonial, 5 bedroom, 3 floors 2200 sqft. The old system is pretty comfortable for the whole house. I was looking at replacing my aging system it with the Mr Cool ducted but I could not decide whether to get the 2-3 or 4-5 ton universal. I live in Northeast Ohio. Please advice.

    1. If your current system heats and cools your home sufficiently, we wouldn’t recommend going with the larger system. It would probably be best to stick with the 2-3 ton system.

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