What Size Mini Split For 24×24 Garage

A garage air conditioner can be a wise investment. Although we don’t use the garage every time, as our living rooms, a garage mini split heat pump means less hot air will transfer to your main home. 

If your home has multi-zone mini split heat pumps already, you can add on another indoor unit for the garage, depending on the system capabilities.

Additionally, many people store various items in the garage, from gardening tools like shovels and hoses to potting oil and melting ice. Ensuring the best air conditions can help prolong the lives and usefulness of these items. 

This guide focuses on finding the right-size mini split heat pump units (heating and cooling) for your garage to avoid the consequences of an undersized or oversize AC. 

What’s the Ideal Mini-split size for a Garage?

A medium-sized single-car garage requires 6,000 to 9,000 BTUs worth of cooling. This equates to 0.5 tons to 0.75 tons. Meanwhile, a standard two-car garage requires 9,000 BTUs to 12,000 BTUs, equivalent to 0.75 tons to 1.0 tons. 

With this versatility comes a need for an efficient heating and cooling system. Fortunately, there are a wide variety of ductless mini split systems that are perfect for garages.

Of course, you may need a bigger air conditioner, depending on the actual size of the garage, your location, and how else you use the garage. 

Why It’s Important to size Your Garage Mini Split Correctly

One of the most common mistakes people make when choosing an air conditioner is thinking bigger is always better. Unfortunately, that’s not always the case. An oversize air conditioner is bad for your garage (and home) just as an undersized unit. 

Dangers of Oversize Mini-Splits

An air conditioner too big for your garage is counterproductive for the following three main reasons;

  • Short-cycling: By size, an oversize air conditioner reaches the thermostat setting quickly, typically within less than five minutes, instead of the standard 10-15 minutes. This is known as short cycling. Short cycling decreases air conditioning efficiency, 
  • Energy inefficiency: Although faster cooling may seem like an energy-saving idea, it isn’t. Air conditioners consume tons of power when starting, much more than when running. Therefore, constant restarts can result in massive energy consumption. 
  • The humidity challenge: Shorter cooling cycles often mean the air conditioner doesn’t get enough time to remove humidity from your home. This can result in cloudy windows, dripping walls, and an increased risk of mold attack. 

Dangers of Undersize Mini-Splits

An air conditioner too small for your garage is just as dangerous. The following are a few risks associated with an undersized AC;

  • Insufficient air conditioning: An undersized mini-split system will certainly not meet your air conditioning needs. In other words, you may not feel as cool as you’d hoped. Of course, the dehumidification process would also be affected. 
  • Appliance burnout: A ductless mini-split system follows the directions of the thermostat. Therefore, even a small air conditioner will try to achieve the thermostat setting, even if struggling. This can quickly result in appliance burnout, potentially causing frequent breakdowns. It may also shorten the appliance’s lifespan. 

Factors Affecting Garage Mini-split sizing

So, you’re probably wondering how to determine the correct mini-split unit size for your garage. The following are six key factors to consider;

Garage Size

The size of the air conditioner you need for a garage primarily depends on the size of the garage. Even if it’s a single-car garage, how big is it?

If you’re not interested in getting into calculations and all the details, we recommend working off the DOE’s recommendation of 20 BTUs per square foot. This means you need about 8,000 BTU for a 20 x 20 (400 square foot) garage and 6,000 BTU for a smaller 15 x 10 (300 square-foot) garage. 

Working with the formula, you’ll find that, generally, you need the following air conditioner sizes for single-car, 2-car, and 3-car+ garages. 

  • Single-car garage: You need a 9,000 BTU air conditioner, equivalent to ¾ tons, for a single-car garage. 
  • Standard 2-car garage: You need a 12,000 BTU, or one-ton, air conditioner for a standard two-car garage. 
  • Large 2-car garage or standard 3-car garage: You need approximately 18,000 BTUs, equivalent to 1.5 tons, of air conditioning energy to sufficiently serve a large 20car garage or standard 3-car garage.
  • Large 3-car garage or garage for more cars: You need a 24,000 BTU air conditioner for a large 3-car garage or a garage designed for four or more cars. 

Remember that these figures apply to standard cars. You may need special arrangements for special motor vehicles. 

2. Ceiling Height

Before mentioning the more technical considerations, we must add that the garage’s ceiling height is an important component of the size. Many people overlook it because most garages have a standard height, i.e., eight feet. 

However, what if your garage is different? What if your ceiling is lower? What if it’s higher? You must adjust the BTU requirements as appropriate to achieve optimal comfort levels. 

We recommend adjusting the required BTU value by 20% for every one-foot change in ceiling height. This means that you need to add 20% more BTUs for every foot’s increase in ceiling height and deduct 20% for every decrease in ceiling height. 

So, for example, the 20 x 20-foot garage needs 120% x 8,000 = 9,600 BTUs, instead of 8,000 BTUs. Meanwhile, the 15 x 20-foot garage would require 120% x 6,000 = 7,200 BTUs, instead of 6,000 BTUs. 

However, if the garage has a lower ceiling, say seven feet, you need to reduce the BTU requirement by 20%. Therefore, 8,000 becomes 6,400 BTUs and 6,000 BTUs becomes 4,800 BTUs.

3. Insulation 

Just as important as the garage size of the garage’s insulation quality. Is your garage properly insulated? Or are you making do with an uninsulated garage? 

This is important because the 20 BTU per-square-foot rule only applies to garages with standard insulation. You need to adjust the values for poorly insulated garages or those with exceptional insulation. 

Generally, you can get away with 15 BTUs per square foot for garages with excellent insulation. So, assuming it’s a standard-height garage, you only need 6,000 BTUs (instead of 8,000 BTUs) for a 20 x 20-foot garage and 4,500 BTUs for a 15 x 20-foot garage. 

Meanwhile, you should consider allocating 25 BTUs per square foot for poorly insulated garages instead of the standard 20 BTUs per foot. 

This means you need a 10,000 BTU air conditioner (instead of an 8,000 BTU unit) for a standard-height 20 x 20-foot garage. Meanwhile, you need 7,500 BTUs for a 15 x 20-foot garage instead of the standard 6,000 BTUs. Always round off to the next round figure if the need arises. 

4. Efficiency Rating (SEER and HSPF)

Another critical factor is the air conditioner’s efficiency rating. Air conditioners have a Seasonal Energy Efficiency Rating (SEER) that indicates how much of the power the AC draws from your power outlets goes to meaningful use.

The higher the SEER value, the more efficient the AC. Meanwhile, the Heating Seasonal Performance Factor (HSPF) refers to heating efficiency for dual-purpose heat pumps. 

The SEER value can indirectly help you select the correct-size AC, indicating the losses you need to cover. For instance, a 90% SEER air conditioner uses 90% of the electricity to bring cool air into your home, meaning only 10% of the power goes to waste. Meanwhile, a 70% SEER unit wastes 30% of all the power it draws.

In short, a lower SEER rating means you need a bigger AC (more BTUs) to achieve the desired cooling. For instance, if you’ve determined that you need 12,000 BTUs to cool your garage but can only find 70% SEER units, you may need to purchase a (12,000 x 100%)/70% = 17,142.85 BTU AC to meet your needs. 

Fortunately, mini-split air conditioners are very energy efficient. Most of the units are rated 99% efficient or higher. 

5. Local Climate

Your local climate has a big impact on air conditioner sizing, even for the main house. Why? Because you can’t compare an 80-degree summer with a 120-degree summer.

One only needs mild air conditioning, while the other requires a powerful system that can bring down the temperatures by up to 50 degrees. 

The good news is that HVAC experts have designed zonal maps to make it very easy to determine how much air conditioning you need based on where you live. 


Other factors that may impact garage air conditioner sizing are whether the garage is attached or detached and exposure to direct sunlight. Generally, you need a bigger air conditioner for a detached garage. You also need more cooling BTUs if your garage is directly exposed to the sun. 

Cost to Install a Mini-Split in Your Garage

Now that you know how to size a garage mini split air conditioner, you may want to know the cost to install one. Heat pump mini split units are the easiest kits to install.

Unfortunately, this is one of the main challenges when installing a mini-split – the installation costs are very high, often into tens of thousands of dollars. 

Nevertheless, it’s still nice to have a rough idea of what you’ll likely pay to prepare accordingly. So, here’s what you need to know;

  • Generally, it costs as much to install mini split air conditioner as to purchase it. This means that if you buy your mini split air conditioner at $2,500, you should expect to pay around $2,500 for the installation. 
  • You may need to purchase several additional materials. For instance, some mini split air conditioner kits don’t include a wall bracket for the outdoor unit. Depending on the AC brand and size, these brackets typically cost $150 to $300. These little costs can further add to the installation budget. 
  • The installation location has a big impact on price. This applies to both the geographic location (where you live) and the location of the AC within the garage. Attic installations, for instance, are slightly more expensive because of the associated risks. So, you need to keep this in mind. 

DIY a Cost-Effective Alternative 

If you have the skills, and most people who work in garages do, DIY installing your garage air conditioner can save you the installation costs. Imagine what you could do with an extra $2,000!

However, purchase a DIY garage mini-split, such as MR.COOL DIY-12-HP-115B25. It comes with a complete DIY kit, making your work easier. More importantly, don’t hesitate to hire an electrician for the wiring. 

Best Ductless Mini Split Air Conditioners For Garage

1. PIONEER Air Conditioner Pioneer Mini Split Heatpump

Pioneer Air Conditioner WYS012A-20 Wall Mount...
  • Save money all year-round with a highly efficient ductless mini split inverter+ heat pump system
  • Ultra-silent and beautifully built perfect for home or light commercial use
  • Comes with every needed component in the box, including an easy-install 16ft copper piping kit
  • Use for both cooling and heating: 12000 BTU/hour with 19 SEER and 10 HSPF efficiency
  • Free tech support and a 5 year coverage on the compressor
  • Voltage 110 120 VAC 60 Hz (standard household power l-n-g)

If you are on a budget and only looking to cool only your garage, consider Pioneer WYS009AMFI19RL mini-split heat pump. It provides 9000 BTU of cooling power for garage spaces up to 400 square feet. It also has a supplemental heat pump that will keep the room in the winter, eliminating the need for two separate garage air conditioners.

While it’s one of the affordable ductless air conditioners on the market, the company also backs it up with 5-Year Limited Compressor Warranty and 2-Year Limited Parts Warranty. Setting it up is easy because all the installation materials are included. However, it is advised that you hire an HVAC technician to help with the installation.

Like many homeowners, we all want to save energy when running our appliances, which is why it’s important always to check the seasonal energy efficiency ratio (SEER) of any mini-split system you want to buy. SEER measures how much heat a system removes from space for each unit of energy it consumes.

Like many homeowners, we all want to save energy when running our appliances, which is why it’s important always to check the seasonal energy efficiency ratio (SEER) of any mini-split system you want to buy. SEER measures how much heat a system removes from space for each unit of energy it consumes.

Pioneer WYS009AMFI19RL garage air conditioner has an impressive 19 SEER, making it one of the most energy-efficient mini-split units on the market. Moreover, it uses a variable speed rotary compressor and inverter technology to regulate energy output.


  • Affordable
  • Energy efficient
  • Multiple modes for year-round comfort
  • Near-silent operation
  • It comes with a complete installation kit


  • The outdoor and indoor garage air conditioners need to be installed by a professional.

2. Senville 9000 BTU SENA-09HF/Z Energy Star Mini Split Air Conditioner Heat Pump

Senville SENA-09HF/Z Mini Split Air Conditioner...
  • Designed for ultra high efficiency performance in summer & winter with our wall-mounted ductless mini split air conditioner & heat pump. Built with Low Ambient Cooling (-5°F) or (-20°C) and Cold-Climate Heating (-22°F) or (-30°C).
  • ENERGY STAR Certified to minimize energy consumption & reduce utility costs. Makes cooling & heating affordable & efficient in most climates.
  • Cooling, Heating, Turbo, and Dry Modes. Inverter Technology. Remote control. WiFi enabled, compatible with Google Home Assistant. Ductless design makes it easy to install an affordable HVAC system in your home or business. Great for any space, including living rooms, kitchens, restaurants, garages & workshops.
  • Important Note: Requires professional installation & must be connected to an electrical panel. Uses 208-230V, ETL Intertek Approved, AHRI Certified. System is pre-charged with R410a refrigerant for 25 ft. Line-set (installation kit) does not come pre-charged, and is designed for professional use.
  • Includes 16 ft. installation kit with communication wire & drain hose.

Engineered for ultra-quiet operation, this AURA Series mini-split is a powerful AC/heater combo ideal for both residential and business applications.

It has onboard sensors that allow you to maintain the perfect temperature in any room during cold weather. Aside from air conditioning and heating, the SENA also features a built-in dehumidifier and fan-only mode.

The garage air conditioner is designed for the coldest climates, with an arctic function that allows for heating in temperatures as low as -22°F/-30°C. An auto-switch mode flips from cooling to heating with a press of a button.

The portable air conditioner unit has a Turbo Mode for maximum cooling or heating and Quiet Mode for low-noise operation. All these functions are controlled through remote control (remote included) or wirelessly from your smartphone.

The package comes with the full installation kit, including a 16-foot copper line set (w/wiring harness). It is 25 SEER rated, R410A pre-charged up to 25 feet, and uses 208V to 230V outlets. It’s also ETL Intertek Approved, Energy Star Certified, and AHRI Certified.


  • High-quality design
  • AC/heater combo
  • Wi-Fi smart control
  • 25 SEER rating
  • Energy efficient
  • Energy Star certified
  • 2-year parts, 7-year compressor warranty


  • Ideal for smaller (100-450 square feet) spaces
  • Requires a 230V outlet

3. MRCOOL Comfort Made Simple Mini Split Air Conditioner and Heat Pump System

12k BTU 17.5 SEER MrCool DIY Ductless Heat Pump...
  • New SmartHVAC app: wifi control - compatible with Amazon Alexa and Google assistant - you can control your DIY anywhere with your Apple or android smart device and an Internet connection. Auto restart: never lift a finger - power outage? don’t worry, the Mrcool DIY auto restart will have the unit running again in no time at all.
  • Easy DIY installation: 25ft quick connect line doesn't require special tools, equipment, or training. Gold fin condenser: corrosion resistant - live on the coast? don’t worry, our condenser is built to resist long term corrosion
  • Variable-speed DC inverter compressor technology increases energy efficiency compared to other mini-split air conditioning units. SLEEP mode on remote:Sleep mode will automatically adjust the temperature to maximize comfort during night time sleep. When in COOL mode, the unit will increase the temperature by 2°F after 1 hour, and will increase an additional 2°F after another hour. When in HEAT mode, the unit will decrease the temperature by 2°F after 1 hour, and will decrease an additional 2°F after another hour.After 7 hours operating in SLEEP mode, the system will switch off automatically.
  • Low ambient cooling: cooling down to 5°F - this feature makes the Mrcool DIY the ideal system for computer server rooms, greenhouses, and any other application that requires cooling all year. Follow me feature: by pressing the 'follow me' button and keeping the remote close to you, you tell the air conditioner to set the temperature from wherever the remote happens to be, this counteracts the tendency for the air conditioner to stop cooling or heating because the air around the unit has reached its set temperature
  • LEAKAGE DETECTION: Protecting Your Investment - When the MRCOOL DIY detects low coolant an alarm will sound to alert you to the problem. This will prevent damage to the compressor while you maintain high air comfort.

You’ve likely heard about smart home appliances that are controllable from devices such as Amazon Alexa. Well, this MRCOOL best garage air conditioners is one of them. Controllable via Alexa or even Google Assistant, it’s a cutting-edge mini split that defines innovation. You can also communicate with the AC from anywhere using your Apple device.

Other than the smart control, the MRCOOL heat pumps incorporate auto-restart, so you never have to lift a finger. Auto-restart proves especially useful when the power goes off.

When power returns, this best garage air conditioner will resume operation at the previous setting. The easy-to-install DIY mini split includes a 25-foot quick-connect line that doesn’t require special tools. The corrosion-resistant condenser is built for durability.

Other features of the MRCOOL include the variable-speed DC inverter compressor technology for increased energy efficiency, the energy-saving Sleep Mode, and leakage detection. This window air conditioner model has a cooling capacity of 12,000 BTU (at 17.5 SEER) and a heating capacity of 12,000 BTU (at 8.8 HSPF).


  • Uses standard 110/120V outlet
  • Ideal for up to 500 square feet
  • Smart (Alexa/Google Assistant-controlled) AC
  • Low ambient cooling down to 5°F


  • Requires professional installation
  • A bit pricey

4. Daikin Wall-Mounted Ductless Mini-Split Inverter Air Conditioner Heat Pump System

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Daikin heat pumps are a world-beater when it comes to home heating and cooling, and this wall-mounted mini-split is another excellent product from the company.

The garage window air conditioner unit blends seamlessly with most decors (modern or traditional) and is integrated with smart inverter technology with a variable-speed compressor. The 17-Series mini delivers 12,000 British thermal units BTU of cooling energy at 17 SEER and a similar heating output at 9 HSPF.

The garage air conditioner incorporates several features designed to increase efficiency and convenience. You’re guaranteed the utmost comfort from the wide-angle louver design to auto-swing louver operation and several low-noise modes.

Typically, the portable air conditioner unit operates at 37 dB, but the sound levels drop by up to 3 dB when you activate the quiet mode.

This AC uses advanced titanium apatite photocatalytic air-purifying filters to clean and deodorize the air. Bluefin protection technology is used to enhance the cleanliness of the air further while extending the life of the AC. The remote control makes it easy to choose your desired operation modes


  • 17 SEER, 9 HSPF
  • Turbo Mode for fast action
  • Smart inverter technology
  • Quiet at just 37 decibels
  • 10-year parts warranty


  • Requires 230V wiring

5. Innovair Air Conditioner Inverter Ductless Wall Mount Mini Split System Heat Pump

Innovair Air Conditioner Inverter Ductless Wall...
  • High Efficiency AHRI certified Inverter technology Heat Pump ductless mini split system
  • Multiple Modes: Turbo Cool, Sleep Mode, Dehumidifier, Hyper Heat
  • Operates in either AC cooling or Heat Pump heating mode
  • Ready to Install: 16FT Installation Kit Included, Pre-Charged up to 25FT
  • Multiple Protections: Gold-Fin Outdoor, Multi-Layer Filter

The heat pumps we’ve looked at so far are best suited to single-car garages. If you’re looking for a slightly more powerful portable air conditioner unit for a 2-car garage, this model from Innovair would be a wonderful acquisition.

A Quantum Inverter Heat Pump Series AC, the mini-split packs 18,000 BTU of cooling power and diligently goes about the cooling process at 17.6 SEER efficiency. It’s an even stronger heater at 20,000 BTU. The heating element is rated 10.1 HSPF.

The garage air conditioner comes with a 16-foot installation kit and includes an outdoor portable air conditioner pre-charged up to 25 feet. Gold-fin protective condensers ensure effective operation even in the coldest conditions. The mini uses a special multi-layer garage door filter comprising a Vitamin C filter, HEPA filter, Catechin filter, and Aroma filter.

The Innovair garage window air conditioner has a low ambient operation of -5°F and a high ambient operating temperature of 115°F. It’s wirelessly controlled, Wi-Fi ready, and features multiple functions, including Turbo cooling, dehumidification, Sleep Mode, and Hyper Heat.


  • 18,000 BTU AC/20,000 BTU heating
  • Ideal for up to 900 square feet
  • Rated 17.6 SEER, 10.1 HSPF
  • Multi-layer filtration
  • LCD remote control
  • 5-year parts, 7-year compressor warranty


  • 230V wiring required

6. COOPER AND HUNTER Alice Mini Split Ductless Air Conditioner Heat Pump

Cooper & Hunter MIA Series, Mini Split Air...
  • Cooper&Hunter Mia Series 9,000 BTU 20.5 SEER, 21.5 SEER2 110V Ductless Mini Split Air Conditioner Heat Pump UL Listed, AHRI Certified
  • Comes with a smart port adapter to easily turn your units ON and OFF, set the temperature, alternate between C° and F°, switch modes, and adjust the fan speed using your smartphone and a C&H Remote mobile app.
  • Pre-charged with refrigerant. Works for heating with ambient temperature up to 5F°
  • System comes with an Installation Kit including 16ft Pre-Flared and Insulated Copper Line Set, 16ft Communication Wires between Indoor and Outdoor unit, Small Accessories and a 16ft Drainage Extension.
  • This is not a DIY equipment, professional installation is required.Whisper Technology for Quiet Operation, Great for Bedrooms, Additions,Living Rooms and Commercial Applications.
  • You are well protected by a 7 year warranty on the compressor, a 5 year parts warranty. This is not a DIY system, professional installation is required.

Finally, another mini-split ideal for smaller, single-car garages, this garage air conditioner from Cooper and Hunter is a 9,000 BTU air conditioner that also doubles up as a 9,000 BTU heater.

It’s one of the heavier air conditioners on this list, weighing about 107.8 pounds (the other mini split air conditioners mostly weigh under 90 pounds). However, it’s quiet enough to be used even in bedrooms.

The mini-split is fairly efficient at 16 SEER and comes pre-charged with refrigerant. In heating mode, it works in ambient temperatures up to 5°F. A 16-foot copper line set is included as well as communication wires. You, however, need a 208V to 230V outlet. Don’t attempt to use a 110/120 outlet.

The unit is AHRI certified and uses 25-50% less energy compared to electric zone heaters such as forced air furnaces. An I-Action inverter compressor ensures long-term reliability. A 5-year manufacturer warranty protects all the parts, while a 7-year warranty covers the compressor.


  • AC/Heater combo
  • Pre-charged with refrigerant
  • Noise-free operation
  • AHRI Certified
  • 5-year parts warranty


  • 230V wiring required
  • Ideal for smaller garages


What size mini-split for a 24×24 garage? 

The best mini split air conditioner size for a 24 x 24foot (576 square feet) 2-car garage is 12,000 BTUs or one ton. This is assuming a standard ceiling height. 

What size mini-split for 3 car garage? 

A standard 3-car garage is 22 x 28-feet, translating to roughly 650 square feet. Therefore, you need approximately 12,000 BTUs, or one ton, assuming a standard ceiling height. 

What size mini-split for 2 car garage? 

A standard 2-car garage is 20 x 20-feet, translating to 400 square feet. We recommend 9,000 BTUs, or ¾ tons, for this garage size. Don’t under or oversize the AC. 

What size mini-split for a 30×40 garage? 

A 30 x 40-foot garage is a massive garage that can hold four or more cars. Multiply (30 x 40) by 20 BTUs/foot-square to find the ideal BTU size. So, you need about 24,000 BTUs. 

What size mini-split for 1000 sq. ft. garage? 

A 1,000 square-foot garage is enough for three cars or more, depending on the design. You need 1,000 x 20BTUs/square-foot = 20,000 BTUs of air conditioning power for this garage size. 

What size mini-split for a 500 sq ft garage? 

Generally, you need 20 x 500 = 1,000 BTUs of air conditioning power for a 500 square-foot garage. However, you may need slightly more or less depending on the garage’s ceiling height and insulation quality and the air conditioner’s efficiency rating. 


There you go. Now you know how to size a garage mini split air conditioner. Generally, you need to consider three main things when determining the right size AC for your garage – the size of the garage (including the ceiling height), the garage’s insulation quality, and the air conditioner’s efficiency. Contact us if you have any questions.