Mr COOL DIY Mini Split Review: Pros And Cons (2021)

There is nothing like the new Mr COOL DIY mini split series. While the big companies stopped innovating a decade ago, Mr COOL is literally a breath of fresh air of innovation in the HVAC industry. We will review Mr COOL mini-split systems; the trendsetter air conditioning/heat pump system.

Here is the quick outtake of the 3rd generation 12k, 18k, and 24k Mr COOL mini splits:

  • They have a high 20+ SEER rating and 10 HSPF rating (incredibly energy-efficient).
  • They are modernized; modern design, mobile app integration, great appeal.
  • Most importantly, you can DIY the installation.

Here’s the deal:

Installation of a mini-split unit averages at about $3,000.

If you can avoid that cost, you obviously would. Before Mr COOL, only the incredibly technical people managed to DIY a mini-split (barely). With the Mr COOL mini-splits, you get an incredibly efficient, easy to install device.

Here are two conditions to avoid that $3,000 installation cost:

  1. Be just a bit of a technical person (we’re not talking rocket science; basic DIY skills will do).
  2. Buy the Mr COOL DIY unit of appropriate capacity (you have to choose between 12k, 18k, 24k, 36k models – more on that later on).

Mr COOL DIY 3rd generation mini-split units don’t need professional installation. In this Mr COOL mini split review, we will look at 12k, 18k, 24k, and 36k systems.

Here is an interesting part:

All Mr COOL mini splits are the future of air conditioning/heating. However, many people are shocked to find out that some Mr COOL models are better than others.

What really mind boggles some people is why is the smaller 12k unit more expensive than the bigger 18k and even 24k unit. We’ll explain in detail why the 12,000 BTU Mr COOL is such a smart investment.

Let’s first look at the comparison of the Mr COOL DIY mini-split. After that, we’ll explain which device is the best for a certain area and look into the energy-efficiency (the most important factor when buying any mini-split heat pump). We will also review each Mr COOL mini-split system (below the comparison table).

Comparison of Mr COOL DIY Mini Split System

Mr COOL Comparison: BTU (Capacity): Efficiency Specs, Rating, Price:


12,000 BTU Cooling

12,000 BTU Heating

Recommended Area: 500 sq. ft.

SEER rating: 22.0
HSPF rating: 10.0
(Voltage = 115 V)4.9 out of 5 stars


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18,000 BTU Cooling

18,000 BTU Heating

Recommended Area: 750 sq. ft.

SEER rating: 20.0
HSPF rating: 10.0
(Voltage = 230 V)4.7 out of 5 stars


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23,000 BTU Cooling

25,000 BTU Heating

Recommended Area: 1,000 sq. ft.

SEER rating: 20.0
HSPF rating: 10.0
(Voltage = 230 V)4.7 out of 5 stars


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34,500 BTU Cooling

36,000 BTU Heating

Recommended Area: 1,500 sq. ft.

SEER rating: 16.0
HSPF rating: 8.9
(Voltage = 230 V)3.9 out of 5 stars


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Which Mr COOL Mini Split To Choose (Based On Square Footage, Energy Efficiency)

As you can see, Mr COOL makes mini-split with different cooling/heating capacity (measured in BTU; British Thermal Units).

It’s important not to pick a mini-split that’s too big or too small for your needs.

Appropriately sizing a mini-split will lead you to either lower energy-efficiency (can cost $100s/year in electricity costs) or limit the lifespan of the device. Therefore you need to take into account the recommended areas for each Mr COOL DIY mini-split.

Here’s how big a mini-split you need:

  • For 500 sq. ft., choose the 12,000 BTU Mr COOL.
  • For 750 sq. ft., choose the 18,000 BTU Mr COOL.
  • For 1,000 sq. ft., choose the 24,000 BTU Mr COOL.
  • For 1,500 sq. ft., choose the 36,000 BTU Mr COOL.

If you’re somewhere between these recommended areas, you can give us your situation in the comments below or use our BTU calculator here.

Now, let’s look at the most important aspect of every mini-split system:

Energy-Efficiency (SEER And HSPF Rating)

Surprise: When you compare the prices of 12k. vs 18k. vs 24k Mr COOL DIY systems, you might notice that the smallest one (12k) has the same (or even higher) price tag as bigger 18k and 24k units. Energy-efficiency is the key here:

The whole point of buying an efficient Mr COOL mini-split is to reduce future electricity costs. Here we need to look at the specifications:

  • SEER rating (cooling). Industry-standard is 14-16 SEER rating (Mr COOL have 20 SEER rating).
  • HSPF rating (heating). Industry-standard is 8-9 HSPF rating (Mr COOL have 10 HSPF rating).

Based on these ratings, we can determine that Mr COOL mini-split units are any good; in fact, they are exceptional.

Some units are better than others. Here is how we can rank the Mr COOL mini-split systems:

  • 1st Place: 12,000 BTU unit with 22 SEER and 10 HSPF rating.
  • 2nd Place: 18,000 BTU and 24,000 BTU units with 20 SEER and 10 HSPF rating.
  • 3rd Place: 36,000 BTU unit with 16 SEER and 8.9 HSPF rating.

As you can see, the 12k Mr COOL DIY can command a higher price just because of its 22 SEER rating. That means that the 12k unit is about 10% energy-efficient than 18k and 24k. How does that translate into electricity dollars?

Simple: If the seasonal electricity bill for Mr COOL air conditioning is $1,000 for 18k and 24k unit, it will be only $900 for the 12k unit. Essentially:

Extremely efficient 12k Mr COOL can save you $100/year in electricity cost compared to 18k and 24k unit. In 10 years, that’s $1,000.

This is the very reason why the 12k unit can have the same or even higher unit cost compared to 18k and 24k device.

On the other hand, if you look at the SEER and HSPF rating of the 36k unit, you can see that the energy-efficient is not as splendid as the smaller Mr COOL mini-split units. You can find a better 36k unit; however, you won’t find a better 12k, 18k, or 24k unit.

That’s why we’ll review each of the best Mr COOL air conditioners – the 12k, 18k, and 24k.

Mr COOL DIY 12k Review

SEER Rating (Cooling): 22
HSPF Rating (Heating): 10
Cooling Capacity: 12,000 BTU
Heating Capacity: 12,000 BTU
Voltage: 115V
Rating: 4.9 out of 5 stars

The 12k unit by Mr COOL DIY is just remarkable in many aspects. Apart from superb energy-efficiency, it’s a highly modernized mini-split system; the likes you won’t yet see from even the biggest brands such as Mitsubishi or Fujitsu.

One key feature is the new SmartHVAC app. Standard mini-splits are controlled via a remote controller. The Mr COOL 12k can be controlled via iPhone or any Android phone. You don’t even have to leave the couch; increase or decrease the temperature with the scroll.

Of course, we can’t overestimate how essential the energy-efficiency is. In fact, the 12k model is the best mini-split in 2020 purely due to the 22 SEER rating. Its cooling effectiveness is 10% higher than most other mini-split units, including the Mr COOL 18k and 24k units. Add the HSPF heating rating, and you have an eco-friendly mini-split that will last for 15+ years.

The vital ingredient for such high efficiency is the variable-speed DC inverter compressor. This alone can cut the yearly cooling/heating costs by several $100.

The DIY process is easy: you get a pre-charged R-410A 25 quick connect line. You will be able to install the Mr COOL 12k without any specialized tools professional installers use.

On top of that, the 12k is the only Mr COOL DIY unit that runs on 115V. That means you don’t need any electrical work; you have low voltage and low amperage.

All in all, the 12k is the modern trendsetting air conditioner/heat pump. This is the future of all mini-splits.


  • Unbeatable 22 SEER rating with 10 HSPF rating
  • Only Mr COOL DIY unit that runs on 115V (even easier installation)
  • DIY installation saves you about $3,000
  • Affordable price given the low electricity costs you can expect in the next decade or two
  • Only for 500-600 sq. ft. spaces or smaller

Mr COOL DIY 18k Review

SEER Rating (Cooling): 20
HSPF Rating (Heating): 10
Cooling Capacity: 18,000 BTU
Heating Capacity: 18,000 BTU
Voltage: 230V
Rating: 4.7 out of 5 stars

18k units are very popular. You’ll rarely find 20 SEER, 10 HSPF rating mini split; that’s exactly what the Mr COOL 18k offers.

It has a DC-inverter compressor that is quiet and enables such high energy-efficiency.

What is more, it can cool down or heat places that are about 750 sq. ft. big. That means that it will fit well in big living rooms and bedrooms.

You also have all the modernization; not does the 18k have an inverter compressor, you can also use the SmartHVAC app to control it, and it has a modern design. That’s much more appealing than the classic mini-split heat pumps.


  • High 20 SEER and 10 HSPF
  • Can cooling/heat spaces around 750 sq. ft. big (1 big room, or 2 small ones)
  • Low price given the 18,000 BTU of power
  • Needs 230V voltage
  • Combined weight is 222 lbs, you’ll need strong arms for DIY installation

Mr COOL DIY 24k Review

SEER Rating (Cooling): 20
HSPF Rating (Heating): 10
Cooling Capacity: 23,000 BTU
Heating Capacity: 25,000 BTU
Voltage: 230V
Rating: 4.7 out of 5 stars

24k unit is the biggest Mr COOL unit that has a 20 SEER rating. You will also notice a bit of discrepancy as far as the cooling and heating capacity is concerned; the cooling capacity is 23,000 BTU and the heating capacity is 25,000 BTU.

This is the most popular big 1 zone mini-split unit. That means that you can use it to cool/heat the entire flat or several rooms. The total recommended area of use is 1,000 sq ft.

It’s quite an achievement that the 20 SEER (and 10 HSPF) can be achieved; higher capacity mini-splits usually have much lower energy efficiency.

All in all, if you need a bigger Mr COOL mini-split, this is the right choice. Needless to say, you will be able to DIY the installation and save yourself $3,000 installation cost.


  • Innovative big 24,000 BTU Mr COOL air conditioner
  • Managed to keep the high 20 SEER rating
  • Very quiet heat pump with low noise levels (like all Mr COOL units)
  • Can handle about 1,000 sq. ft. of space (entire flat, or several rooms)
  • Affordable price (below $2,000) for such a big device
  • Installation is a bit tougher due to a larger device
  • You will need 230V (but no amp breakers in most cases)

Verdict On Mr COOL

Undoubtely, the Mr COOL DIY mini-split units are the way of the future. The innovation is seen everywhere; from the design, DC inverter compressor, and WiFi connectivity to the SmartHVAC app.

In the future, we’re likely to see other companies following the Mr COOL footsteps. However, as of now, nobody has managed to snatch the holy grail of mini-splits:

To create a mini-split that everybody could DIY with ease.

With Mr COOL, you will not only save yourself the high installation costs, but due to high energy-efficiency, you will see your cooling/heating electricity bill reduced by several $100 per year.

25 thoughts on “Mr COOL DIY Mini Split Review: Pros And Cons (2021)”

  1. My house is a two floor semi with a basement. The stairs are on the outside wall of the house. The building is 29.5 x 19.7 irr ft. The upstairs is about 500ish sq ft and the main floor is the same. Does this make the area to cool about 1000 sq ft?
    I intend to buy a MrCool and install it at the top of the stairs on the 2nd floor. I am guessing that by doing this I will be able to cool both the top and main floors. Is this correct? Which MrCool should I buy?

    • Hello George, two-floor houses usually required 2 units. If you go with the bigger 24k unit, it could (in theory) cool both floors, if you just look at the square footage. However, the distribution of air from a single unit can hardly cover 2-floors. Cool air does have a higher density than hot air, and 2nd story unit cold provides a cooling effect to the 1st floor because cool air will be dissipated in the lower floor. Unfortunately, that will probably not be enough.

      For your situation, you would require 2 units; the most optimum would be 2x 12k MrCOOL units here. 1 unit for the 1st 500 sq ft floor and the second for the 2nd 500 sq ft floor. The added advantage here is that you will need less airflow to cool both places; this translated into a quieter operation. 12k MrCool is the quietest unit with 38/31.5/23.5 dB indoor noise levels for high/mid/low fan speed setting; other units generate well over 40 dB noise levels. Hope this helps.

  2. Hi. I’m interested in your DIY Single Zone unit. It’s going into a 22′ X 22′ garage shop with 9.5 foot ceilings. That’s about 484 square feet, but I have a 16 foot garage door to contend with for possible air infiltration. The ceiling is insulated and I’m planning on insulating the walls. I’m in Virginia Beach, so temperatures range from a high of about 105 in summer to 15 in the winter. I’m also already wired outside for a 220V disconnect, so I think the ton and a half unit (18K) is what I need.

    My primary question is whether shorter supply lines are available? It looks like the standard package is a 16 foot line. I’m planning to run the lines inside the wall between the studs to the outside and I’m estimating at most a 9 to 10 foot run. I would prefer not to have a 6-7 foot coil of gas line on the exterior of the house.

    • Hello Scott, your BTU estimate checks out. The 16-foot line is the standard length, and it’s really difficult to use a different one. Usually, you could buy an additional 10 ft supply line but the whole point of Mr COOL DIY units is that you get everything in the box (standard measures). If you’re a bit crafty, you could try to hide that 6 ft of the line you don’t need inside the walls. Running it on the exterior of the house doesn’t really look aesthetic, you’re right.

  3. I have a 2000 square foot spray foam insulated shop. 300 square feet is office space and the remaining 1700 is open shop space. Would like to have 2 interior units so when cooling or heating the shop area isn’t needed I can cool or heat the office only. What size btu unit do you recommend?

    • Hello Marc, let’s presume the shop and the office have 8 ft ceiling. The combined square footage (2000 sq ft) would require a minimum of 40,000 BTU cooling/heating output. 2 x 24,000 BTU Mr COOL units should do the job very well. The specific serial number of units is DIY-24-HP-230B and you can check them here. The recommended coverage area is exactly 1,000 sq ft; so for shop + office you just install 2 units.

  4. Standard mini-splits are controlled via a remote controller. The Mr COOL 12k can be controlled via iPhone or any Android phone. You don’t even have to leave the couch; increase or decrease the temperature with the scroll.

  5. Hello, I live in Kentucky and have hot and humid weather. I have a 1600 square foot shop with 12 foot ceilings. The building is insulated very well. Would the 36k btu mr. cool unit be enough to cool my building. Thanks!

    • Hello Logan, the DOE’s rule of thumb states ’20 BTU per sq ft if you have 8 ft ceiling’. You have 12 ft ceiling; so let’s say you would need at least 30 BTU per sq ft. 1600 sq ft * 30 BTU per sq ft = 48,000 BTU. Hence, in your situation, the 36,000 BTU Mr COOL would not be sufficient. The better and more adequate solution would be two 24k Mr COOL units with a combined cooling output of 48,000 BTU. Hope this helps.

  6. I have a modular ranch house built 1984, approximately 1000 sq ft. The living room, dining room and kitchen are all one room with a 1/2 vaulted ceiling in the dinning room/living room combination and a 8 ft ceiling in the kitchen. I also have afi used basement with a one car garage underneath. This is an all electric house. I put in a propane stove in the living/dining room for heat in the winter. 2 bedrooms and bath, all on one floor. How many mini splits should I buy as I want to use it for heat and air conditioning?

    • Hello Barbara, for a 1000 sq ft ranch house you would need a total cooling output of about 20,000 BTU. But this is a modular house with several rooms; you will need 2 air handlers to homogeneously cool and heat the house. If you go with Mr Cool, the most optimum option are two Mr COOL DIY 12k units; 1st air handler should be in the living room and the 2nd one in the kitchen.

  7. Hello,
    I’m planning on buying the 12K DIY Model and want to run it on my solar (3kW) with a battery bank of 12,000 W hours. Right now, I have a through the wall 12,000 BTU just A/C and when I plugged it in to Solar, for some reason my voltage kept dropping on my inverter, So I can’t run it off Solar. With this one, could I splice an extension cord onto the electrical leads and either plug it into the electric company or my solar? I believe this one will work with Solar because it has a lot lower amperage (2.5A) and would only use about 300W on low. How many Watts does the medium setting use? Thanks.

    • Hello Bill, the dropping voltage is concerning. Usually the voltage remains the same, and amps and watts change. Splicing extension cord might work; it’s really hard to know for sure, however. 12K DIY model has max. wattage of 960W (based on 12.5 EER rating) and max. cooling amperage of 15A. 300W is a bit low; at 300W, you would be getting about 3,750 BTU cooling output. The medium setting still has 500W+ wattage and requires at least 5 amps. Hope this helps a bit.

  8. I have a two story house – 4 bedroom upstairs about 1,250 sq feet, downstairs about 1,100. Would the 36k mini-split with 4 zone attachments work fine for this?

    SoCal by the beach so would use in the hot august/September months but rarely above 80-85.

    • Hello Chris, for a combined 2,350 sq ft, you would require 47,000 BTU unit, given the ’20 BTU per sq ft’ rule of thumb. 36k unit might even be enough; you can always get an additional 14,000 BTU portable unit, for example, if you find the air conditioning insufficient.

  9. I ordered a 36000 btu diy mr cool unit the other day but I was going to put it on a 30 amp breaker. Now I’m seeing I might need a 40 amp breaker? Does this mean I can run it at half power or something like that? Thanks in advance if anybody as some answers

    • Hello Colin, this question would be best answered by Mr Cool guys. We can theorize a bit here but they have the practical measurements and will give you the clearest and most realistic answer.

  10. I have a shed that i insulated that is 12foot x 16foot and the total height is 12 feet. I live in the dallas/ft.worth area and can get quite hot. What is the recommended unit size i need for such intense texas heat?

    • Hello Bill, 12×16 is combined square footage of 192 sq ft. For 8 ft ceilings and standard climate, you should use the ’20 BTU per sq ft’ rule of thumb. With a 50% higher ceiling (12 ft), that’s about 30 BTU per sq ft. Factor in the intense Texas heat, and you’re looking at 40-45 BTU per sq ft. At 45, you’re looking at 8,640 BTU; 10,000 BTU to be safe. That said, the Mr Cool 12k BTU would not be overkill. You just run it on a lower speed setting for optimum cooling capacity output.

    • Hello Patrick, all air conditioners have a dehumidifier built-in. With Mr Cool units (12,000 BTU) included, you can even set them into ‘Dehumidifier mode’.

  11. Hello- what is the maximum run allowed to connect the indoor and outdoor units? We knocked down a bunch of walls to make our first floor open concept and added windows. So now the only wall space I have to permanently mount the indoor air handler is on an exterior wall but against my attached garage. So we would have to run the supply lines through the garage to the exterior unit. It would be 23.5 feet just to reach the outdoors, then down from there to reach the unit on the ground. Is this length prohibitive for mini splits?

    • Hello Christina, the max. length is 25 feet. The standard length is 16 feet; Mr Cool units have an above-average refrigerant line length. Now, having knocked down a bunch of walls and having 23.5 feet just to reach the outdoor is quite an uncomfortable situation to be in. You’re only left with 1.5 feet to reach the unit on the ground; which probably won’t be enough. We are sadly not aware of any mini-split with 25+ feet refrigerant lines. Hope you find this at least a bit helpful.

  12. Hello, We have a 1400 sq ft home in CT. 700 sq ft are a great room with a 9 ft cathedral (kitchen, living and dining room). 700 sq ft are 3 bedrooms, 2 bath and a hallway. We want to DIY install 2 Mr. Cool mini-splits, 1 18,000 btu unit in he great room and 1 12,000 btu unit in the bedroom (13 x 13) that is at the end of the hallway and faces the great room. Are these the correct units to buy or do you suggest another size? We want to make sure we do this correctly, soany and all info is appreciated. Thanks

    • Hello Mary, you’re correct, it’s best to make sure your BTUs are adequate for the size of your home. It’s usually recommended to use the ’20 BTU per sq ft’ rule of thumb with these calculations. The 18,000 BTU unit for the great room (700 sq ft) would be sufficient; you’re lookt at about 25 BTUs per sq ft.

      The 2nd unit (in the bedroom) should be larger. Correct me if I’m wrong, but it should cool down combined square footage of 700 sq ft? 12,000 BTU unit won’t suffice for 700 sq ft, unfortunately. 18,000 BTU would be a better choice. Hope this helps a bit.


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