Best Air Conditioner For Garage With No Windows 2025

The garages that lack windows may be very hot and stuffy, particularly during summer. These enclosed spaces become hot very fast without ventilation.

The positive thing is that there exist special air conditioners which can cool a windowless garage.

The comparison of the best AC units (portable, mini-split, through-wall, and evaporative) is provided below to assist you in selecting the most suitable one regarding the size of your garage and its requirements.

Top Air Conditioners for Windowless Garages – Detailed Reviews

#1 Senville LETO Series 12,000 BTU Mini Split Air Conditioner Heat Pump

Senville LETO 12,000 BTU mini-split system is a great option to cool a non-windowed garage, particularly a larger two or a three-car garage. This is a ductless air conditioner that is fixed on the wall and is connected to an external condenser, hence does not need a window to be installed.

It has 12,000 BTU of cooling capacity (1 ton) and can easily air condition a space of approximately 600-750 sq. ft. when well insulated. Since it is a heat pump, it can also heat your garage during winter, which means that it can give you climate control throughout the year.

The Senville unit has an inverter compressor that is highly rated in terms of efficiency (SEER 20+), which implies that it will operate at a variable speed to keep the desired temperature without consuming much energy. The inverter technology in practice, maintains low power bills and prevents on/off cycling of less efficient units.

The system also has the option of an Eco Mode (~75 o F) which can save even more energy when the conditions are mild. The fact that the Senville is very quiet is also a plus to many of its users since it can run as low as 41 dB indoors at the lowest fan speed. This sound level is approximately equal to a casual conversation, and thus, it will not be disturbing in case you use your garage as a workshop or a gym.

Mini-split is more complex to install than a portable AC but Senville simplifies the process by providing 16-foot copper line set, control cable, and mounting bracket in the kit. (Note that you might have to purchase or rent a vacuum pump and some special tools to install it yourself, or to hire a professional HVAC installer.)

The unit operates on the standard 115V power, so there is no need to have special wiring in most garages. After installing, it is quite convenient to use it, you are provided with a remote control and the system is also Alexa-enabled, which means you can control temperature and settings via voice or app.

Altogether, Senville LETO Series mini split is a high-powered cooling device, ultra-quiet, and heating system, which is the best premium option to use in the case of windowless garages where people want to have a permanent and efficient solution.

#2 Dreo 12,000 BTU Smart Inverter Portable Air Conditioner

In case you want a portable device that you do not need to install permanently, the Dreo 12,000 BTU Smart Portable AC is an outstanding option. It is a wheeled floor-standing unit that you can relocate anytime, and it is made to exhaust hot air by using an exhaust hose.

Although it is a single-hose portable AC (it takes air inside the room and releases hot air outside), the modern inverter technology makes the Dreo stand out among the ordinary portables. Its inverter compressor enables it to operate more efficiently and steadily and this has enabled it to gain a reputation of fast cooling and low noise. Having 12,000 BTU (ASHRAE) cooling capacity, the Dreo can cool approximately 300-350 sq. ft. of space, which is perfect to cool a one or two-car garage.

The quiet operation is one of the features of this unit. The Dreo has a low fan speed rating of just around 46 dB, which is remarkably silent of a portable AC. At faster speeds, the sound is still described by the users as a soft white noise that can be easily ignored.

This implies that you can easily work in the garage without a loud compressor turning on and off every now and then. During testing, the Dreo was able to reduce the temperature of an uninsulated garage that was 80 degrees Fahrenheit to 70 degrees Fahrenheit in 45 minutes even though it was almost 98 degrees Fahrenheit outside. Its strong compressor and effective design contribute to that high speed.

Another great advantage of this AC is the so-called smart features. It has in-built Wi-Fi which enables you to connect it to the Dreo app or voice assistants. You can change temperatures, use timers or modes using your phone or Alexa/Google Assistant.

It is also convenient when you would like to have the garage cooled down by the time you enter it. The unit also has a conventional remote control which can be used directly. Similar to the majority of portable ACs, the Dreo also has several modes (Cool, Dry dehumidifier, and Fan-only). It has a window exhaust kit – in case you have a windowless garage, you may modify this kit to exhaust through a hole in the wall, or even under the garage door with a good seal. The Dreo 12,000 BTU portable AC with its inverter efficiency, silent performance, and intelligent controls is the perfect option in case you want to find a balance between convenience and performance in a garage without windows.

#3 Midea Duo 12,000 BTU Smart Inverter Portable Air Conditioner

Another top performer is the Midea Duo 12,000 BTU Portable Air Conditioner which is suitable in garages that do not have windows. The Duo series of Midea has a distinctive, hose-in-hose or dual-hose design, which is much more efficient at cooling than single-hose portables.

Basically, it contains both an inner and an outer hose assembly: one of them draws in outside air to cool the condenser and another one pushes hot air out of it. This implies that the unit does not generate negative pressure in the room or draw warm air through cracks and this is a major plus in a closed garage. Having a 12,000 BTU cooling capacity (high SACC rating of ~10,000 BTU), the Midea Duo can easily cool rooms of up to ~450 sq. ft., which makes it a good fit in most two-car garages or large one-car workshops.

The Midea Duo has an inverter compressor and two-hose system that provides quick and even cooling and consumes less power than the older portables. It has the ability to lower the temperature of your garage fast and sustain it without switching on and off.

The other outstanding aspect is the quietness. The Midea Duo is as low as 42 dB on its quiet setting, which is extremely low considering that it is a unit of this size. The sound is mostly simply air flowing; the compressor hum is quite low. This allows one to be able to work on projects or do exercises in the garage with little interference.

This model is also an intelligent device Wi-Fi is also available and the model can be operated through the Midea Air smartphone app or voice control (Alexa/Google Assistant). It is possible to configure remotely or arrange schedules.

The unit is physically somewhat large and heavy (approximately 70 lbs), however, it is on casters to be rolled. It includes a sliding window panel that the hose can be attached to; in a garage that has no windows, a user usually installs a dryer vent or port through the wall to connect the hose assembly, or a door/window that is cracked open with the panel. The Midea Duo also has dehumidification that comes in handy in humid regions to make your garage dry during cooling. On the whole, the Midea Duo 12,000 BTU is one of the most efficient and quiet portable ACs that can be offered, and it can effortlessly cool a windowless garage when ventilated properly.

#4 Whynter ARC-14S 14,000 BTU Dual-Hose Portable Air Conditioner

The Whynter ARC-14S is a tried and tested option in case one has a large garage or requires the highest cooling capacity of a portable unit. It is a 14,000 BTU (9,500 BTU SACC) two-hose portable air conditioner which has been a favorite of heavy-duty cooling applications over the past few years.

It has a dual-hose system where one hose is used to draw outside air and the other one to release hot air, thereby cooling more effectively and faster in an enclosed area such as a garage. The Whynter has a full 14,000 BTU and can cover up to approximately 500 sq. ft. (which is perfect in a large 2 car or even some 3 car garages), but again, this will vary depending on the insulation and surrounding heat of the garage.

ARC-14S is well-built and is available in black and platinum color scheme. It has three operating modes: Cool, Fan and a Dehumidify mode that is capable of taking a lot of moisture out of the air (useful in case your garage is humid).

The Whynter is quite strong during operation, it has the capacity to lower temperatures within a short time. It has been reported by users that it can turn an otherwise sweltering garage into a place where one can work as long as the garage door is closed and the unit is well ventilated. The dual hose system makes sure that it is not working against itself by pulling in hot air as is the case with single-hose systems.

Although it is not the most silent one compared to the inverter-based models such as Midea or Dreo, the noise level of the Whynter is quite acceptable given its size (about 53 56 dB at the max). You will notice compressor and fan, but the sound is similar to a loud fan or window AC.

People are willing to accept this trade-off considering its output. It also has an auto-evaporation condensate system in most conditions, thus you do not have to empty water very often (in extremely humid climates it has a drain port in case of need).

The unit is around 80 lbs but it is equipped with caster wheels to move the unit around. It is easy to install: it has a window kit with two hoses. In a garage without windows, most of the people run the hoses through a hole in a wall or through an adapted piece in the door opening. Due to its performance and high cooling capacity, the Whynter ARC-14S is still one of the best choices to keep cool in a windowless garage, particularly when a typical 14,000 BTU portable is required to turn the room into an acceptable environment.

#5 BLACK+DECKER 8,000 BTU Portable Air Conditioner

The BLACK+DECKER 8,000 BTU Portable AC is a smaller and cheaper cooling option to serve smaller garages or those buyers who are on a budget. This model (BPACT08WT) is a well-known entry-level portable air conditioner that has a lightweight and easy to move.

It is one of the smaller AC units weighing approximately 46 lbs and measuring approximately 15” x 14” x 25”. This is good news in case your garage is small. The 8,000 BTU (ASHRAE) cooling capacity is most appropriate to small spaces, i.e. of the scale of 150 to 250 sq. ft. so it can cool a one-car garage or workshop, or spot-cool a bigger garage, provided it is used close to your work area.

This BLACK+DECKER AC is a 3-in-1 device: it cools, dehumidifies, and it can work as a plain fan. It has a user-friendly electronic control panel on top, and a full-function remote control.

The remote has one convenient feature, the Follow Me mode: the remote itself has a temperature sensor, so the AC will cycle depending on the temperature around the remote. You can leave the remote near your work bench so that the unit cools down until that region is at the temperature you want it to be. This AC has such convenient features as a 24-hour timer and a sleep mode, even though it is smaller. It also has an auto-evaporation system and therefore in most instances you will not have to drain water manually, the condensate is exhausted out with the hot air.

Regarding the installation, it has a window vent kit of the exhaust hose. When you have no window in a garage you can be creative by venting through a small hole in the wall or a garage door vent kit.

The unit is not dual-hose and only 8,000 BTU so it is not going to cool a large area or a very high heat load, though it can certainly make a small garage more comfortable.

As an example, a small uninsulated garage with a stifling 95F temperature may be cooled to a more comfortable 80F on a hot day, and cooler still in an insulated garage by this unit. It is noise-wise rated about 52-55 dB on high, which is noticeable but not loud, and is similar to a box fan.

The advantage of the BLACK+DECKER is its affordability and the ease of use: it is one of the cheaper portable air conditioners. This 8,000 BTU model is a good choice in case your garage is not very large and you are looking for a fast and easy-to-install cooling system that does not require any permanent alterations.

It is particularly helpful to renters or to people who only use the garage occasionally and need a portable unit that can be used in other places as well (it can be easily rolled into a shed or even an indoor room when necessary).

#6 LG 10,000 BTU Through-The-Wall Air Conditioner (LT1016CER)

Through the wall air conditioner is an excellent long-term option when it comes to cooling a windowless garage, and LG LT1016CER 10,000 BTU is one of the best ones in this segment.

This kind of AC is basically a self contained cooling system (very much similar to a window AC) which you fit by making a hole in an outside wall of the garage.

The LG 10k BTU through-the-wall AC is capable of cooling rooms of up to approximately 440 sq. ft. and this is enough to chill a standard two-car garage or a large one-car garage. It is a special 115V unit (does not require special wiring unless the circuit is already loaded) and it is supported and insulated by sliding into a wall sleeve.

LG has a reputation of reliable compressors and easy controls in terms of performance. This unit has three cooling speeds, three fan speeds and a thermostat to determine the temperature you want.

It also includes a pair of handy modes: an Energy Saver mode, which turns the fan on and off periodically to circulate air and only turns the compressor on when it needs to (useful to maintain temperature without overrunning), and a Dry mode, which can remove up to 2.9 pints of moisture per hour as a dehumidifier.

This will make your garage less humid and this is good in case you are storing tools or cars which may be affected by the humidity. 4-way louvers allow you to adjust the direction of the airflow, and you can blow the cool air to the middle of the garage or to the place where you usually spend your time.

The LG through-wall unit is equipped with a full-function remote control that enables you to adjust the settings even when you are at the other side of the garage. It is quite noisy and does not occupy any floor space because it is wall-mounted.

To remember one thing is that installation will require opening a hole in the wall between wall studs (the size of the unit is approximately 24 W x 14.4 H x 20 D). You will probably require an LG or compatible wall sleeve to install it in (although in case your garage wall is unfinished, this can be easier to install).

When installed, through-the-wall ACs such as this are quite safe and permanent in location, no hose or outside unit to be concerned about, merely an exterior grille on the outside.

They are also generally more energy efficient than similar capacity portable ACs. In case you own your garage and do not mind a little DIY or a handyman, the LG 10,000 BTU through-wall AC is a clean and effective cooling solution that does not require having a window.

#7 Hessaire MC26A 2,100 CFM Portable Evaporative Cooler (Swamp Cooler)

A no window garage may have an alternative cooling measure in the form of an evaporative cooler particularly in arid climates. The Hessaire MC26A is a portable evaporative air cooler (sometimes referred to as a swamp cooler) having a high-powered fan with a 2,100 CFM (cubic feet per minute) airflow.

As opposed to the above refrigerated air conditioners, this kind of unit cools the air through evaporation of water. The Hessaire draws warm air into the cooling pads that are wet and as the water evaporates the air becomes cooled and blown into the garage. In perfect conditions, this model is capable of cooling up to 700 square feet, or the size of a two-car garage or more. It is widely used in workshops, garages and patios in places such as the Southwest US where air is hot and dry.

The Hessaire MC26A is very easy to operate, just pour water into its water tank (which has a capacity of about 7.3 gallons) or connect a garden hose to it so that water can be supplied continuously. It is three-speed fan and has oscillating louvers to spread the cool air.

It can lower the perceived temperature in a garage considerably when run at high: e.g. in low-humidity conditions it may take a 95 oF garage to the 80 oF or lower range or even cooler, which is much more comfortable. The other advantage is that it uses much less electricity as compared to a compressor based AC (only around 250 Watts or so), which makes it cheaper to operate over long durations. It also brings in some humidity that is welcome in very dry regions.

There are however a couple of caveats to evaporative coolers. They are most effective in dry air: in a humid climate (e.g. the South or Midwest on a muggy day), they will cool less and will increase the humidity of the garage. In a close garage, you literally have to open a door or a window to allow the moist air to escape; evaporative coolers need some exchange of air.

In practice, you’d crack the garage door or install a vent to let out humid air and bring in drier air. In hot, dry regions, an evaporative cooler is a cost-effective way to make a garage more comfortable (and they use much less electricity). But in humid climates, they are not suitable – on a sticky summer day, they will just make the garage muggy without much cooling benefit. So consider your local climate before choosing this option.

Buying Guide: How to Choose an Air Conditioner for a Garage With No Windows

Types of Air Conditioners Suitable for Windowless Garages

In the case of your garage lacking any windows, the standard window AC units are out of the question, but there are still a number of cooling alternatives to be used. The most common ones are portable air conditioners, ductless mini-split systems, through-the-wall AC, and evaporative coolers.

Both have advantages and disadvantages as far as garage usage is concerned:

• Portable Air Conditioners: These are self-contained units on wheels that expel hot air through an exhaust hose. They are appealing because they require no permanent installation – you just need to vent the hose through an opening (like a door gap, wall vent, or ceiling vent). Portable ACs come in single-hose or dual-hose models. 

  Single-hose units pull air from the garage to cool their condenser and then blow the hot air outside through the hose; this can create slight negative pressure (drawing hot outside air into the garage through cracks). 

  Dual-hose units have one hose drawing outside air in to cool the condenser and a second hose pushing hot air out, which is more efficient for enclosed spaces. Portables are easy to set up and can be moved or stored when not in use.

  The downside is they typically aren’t as efficient as mini-splits or through-wall units and can be a bit noisy. In a windowless garage, you’ll need to create a vent for the hose – many people install a dryer vent in the wall or use a panel to vent under the garage door.

• Ductless Mini-Split AC: A mini-split is a permanent solution consisting of an indoor air handler (mounted on the wall or ceiling) and an outdoor compressor unit, connected by refrigerant lines. They require drilling a hole (about 3 inches) through the wall for the lines and wires, but no large window or opening.

  Mini-splits are highly efficient (often SEER 18-24+) and very quiet inside since the noisy compressor is outside. They also offer heating if you choose a heat pump model, which most are. For a garage, a mini-split can be ideal if you use the space frequently – it will cool effectively even in very hot weather and maintain the set temperature.

  However, the initial cost is higher (equipment and installation can run $800–$2000+). Installation can be DIY for those handy with HVAC (some brands like MRCOOL are marketed as DIY-friendly with precharged lines), but many will opt for professional installation.

  If you are okay with the upfront expense, a mini-split is arguably the most effective and efficient way to cool a garage with no windows.

• Through-the-Wall Air Conditioners: These AC units are similar to window units but are designed to sit in a wall opening instead. You’ll need to cut a hole in an exterior garage wall and install a sleeve that the AC slides into. Through-the-wall units come in various BTU ratings (8,000–14,000+ BTU typically) and can cool medium to large garages.

  They are a good option if you want a permanent unit but don’t want the complexity of a mini-split. They plug into an outlet (115V for smaller units, 230V for larger). Once installed, they don’t take up floor space and you don’t have to manage exhaust hoses. The cooling performance is similar to a window unit – generally quite good – and some models also include heating (heat mode) if desired.

  The drawback is the installation requires modifying the wall. If your garage has a suitable exterior wall, a through-wall AC like the LG we discussed can be an efficient long-term solution.

• Evaporative Coolers (Swamp Coolers): Evaporative coolers are a different technology – they use water evaporation to cool the air and work best in low-humidity environments. They don’t need to be vented out a window because they are not removing heat via a closed refrigerant cycle; instead, they continuously blow air.

  However, they do need airflow – you can’t run them in a sealed garage or the humidity will build up too much.

  In practice, you’d crack the garage door or install a vent to let out humid air and bring in drier air. In hot, dry regions, an evaporative cooler is a cost-effective way to make a garage more comfortable (and they use much less electricity).

  But in humid climates, they are not suitable – on a sticky summer day, they will just make the garage muggy without much cooling benefit. So consider your local climate before choosing this option.

Calculating the BTU Capacity You Need

It is important to choose the appropriate BTU rating (cooling capacity) of AC in your garage. An undersized unit will not be able to cool the area; an oversized one may short-cycle and fail to dehumidify (but in a garage, a little oversizing is not as big a problem as in a house). The following is how to estimate what you need:

• Measure Your Garage’s Square Footage: Calculate the floor area (length x width). For example, a typical 1-car garage might be ~200 sq. ft. (e.g., 10’ x 20’), a 2-car garage around 400–450 sq. ft. (e.g., 20’ x 22’), and a 3-car garage could be 600+ sq. ft.
• General BTU Guideline: Indoor residential spaces often use about 20 BTU per square foot as a base guideline. Garages, however, often have less insulation and more heat-generating contents (vehicles, appliances), so you might need more per sq. ft. For a garage, roughly 30-40 BTU per sq. ft. can be a safer estimate, especially if it’s uninsulated. For instance, a 400 sq. ft. garage might require on the order of 12,000–16,000 BTU to cool effectively. If the garage is well-insulated and shaded, you can lean to the lower end; if it’s sun-baked with no insulation, lean higher.
• Consider Ceiling Height: Many garages have higher ceilings than a typical room (often 9-10 feet, or even more in workshops). If your ceiling is significantly higher than 8 feet, increase the BTU capacity accordingly (e.g., a 400 sq. ft. garage with a 10 ft ceiling has 25% more volume than one with 8 ft, so you’d want perhaps 25% more BTU capacity to compensate).
• Other Heat Loads: Take into account factors like if you’ll be running heat-generating tools or equipment, if the garage has a refrigerator/freezer, or if the garage door is frequently opened (letting in hot air). All these can raise the cooling requirement. For example, working on a running car engine or welding in the garage will add heat – a larger BTU unit or additional fan might be needed for those scenarios.
• When in doubt, go with a little higher BTU: In a garage, it is usually preferable to have some extra capacity because comfort is the main objective (energy efficiency is a bit less important than in a house living room, e.g.). A unit with a higher-BTU will cool the space quicker. Simply make sure that your electrical circuit is suitable to support a larger unit (most portable or window ACs up to ~14,000 BTU can be powered on a typical 115V 15-amp circuit, but beyond that you may need a 20-amp circuit or 230V to power very large units).

As an example: Say you have a 2-car garage (~400 sq. ft.) that is moderately insulated, in a hot climate, then a 12,000 BTU unit may be the minimum. You may consider a model within 12k-14k BTU to have a better performance.

Conversely, a small 150 sq. ft. garage can be okay with an 8,000 BTU portable AC. Remember that, in the case of using an evaporative cooler, they are not sized in BTU, but in CFM of air movement, you would select them by square footage coverage and fan capacity, as given by the manufacturer (e.g., 2100 CFM at 700 sq. ft., etc.).

Ventilation and Installation Considerations

There are certain challenges of installing an air conditioner in a garage that has no windows. You will have to devise a means through which the heat can get out to the outside and also how the unit will be installed in the room.

The following are the important considerations to make on the various types of ACs:

• Ventilation of Portable ACs: Portable AC will have to vent hot air. In a windowless garage, the usual remedies are:Putting a small wall vent (such as a dryer vent) in the exhaust hose. You would make a hole of 5 inches diameter in the wall, and put a vent cap outside, and you would connect the hose with it. This is a clean, permanent solution to venting.Using the garage door: Some will crack the garage door open so that the exhaust hose can be run out. You can even have garage door vent kits or panels that fit in the gap in the door to hold the hose. The negative part is that you will get some leakage of hot air around the door unless it is sealed well. When you use this technique, you may consider weatherstripping or insulation panel around the hose to reduce the amount of hot air entering the hose.Venting through the ceiling or roof: In case you have a gable vent on your garage attic space or you can cut a vent to the roof, you may vent upwards. Hot air rises naturally, so this can work, but it is a more complicated installation and you need to make sure that moisture is controlled (with portable ACs that drip you do not want water pumping into the attic).

Make sure the exhaust hose run is as straight and short as possible; long or kinked hoses reduce efficiency and can cause heat to build up. And if your portable is single-hose, remember that the garage will be slightly negative pressure – so try to seal big air leaks (like under doors) or you’ll be pulling in outside air constantly.

Insulation and Sealing: Maximizing AC Performance

It is worth considering the insulation and sealing of your garage, before you even install an air conditioner. A garage without windows may not have windows, yet the heat may find its way in through the thin walls, an uninsulated garage door or the attic. Enhancing insulation can be a major way of enhancing the effectiveness of your AC:

• Garage Door Insulation: Metal garage doors absorb a lot of heat from the sun. Consider adding insulation panels to the inside of the door. There are DIY garage door insulation kits (foam or fiberglass with a reflective backing) that can be cut and fitted into the door’s recesses. This can reduce the heat radiating into the garage by a considerable amount and also help in winter. Even insulating the door alone can drop the internal temperature by a few degrees on hot days.
• Wall and Ceiling Insulation: Many garages have unfinished walls (exposed studs) with no insulation, and often no ceiling drywall (open to the roof). If feasible, adding insulation in the wall cavities and the attic/ceiling can trap cool air longer. Even storing some foam board against the walls or putting a reflective radiant barrier on the underside of the roof can help reflect heat away. Granted, fully insulating a garage is a project, but if you plan to use AC regularly, the investment pays off in reduced cooling time and better overall comfort.
• Weatherstripping and Air Leaks: Check the gaps under doors (including the big garage door). The garage door should have a bottom seal – if it’s torn or missing, replace it to keep hot air from constantly leaking in at the floor. Likewise, add weatherstripping to the perimeter of the garage door if you see daylight. Seal any gaps around conduits, small holes, or vents in the garage. Essentially, while you will need some venting solution for the AC itself, you want to eliminate unintentional air leaks so you have control over where air enters/exits.
• Roof Radiant Heat: Much heat may be radiated by the ceiling of the garage when the sun is beating on the roof. Attic vents may assist (such as ridge or gable vents to allow the hot air to escape). In other instances individuals will put in attic exhaust fan to blow out hot air above the garage. When your AC is not keeping up, it could be that the attic above is 130F and heating the space, venting or insulating that space will take the load off the AC.

In a nutshell, the less you expose the garage to the outside heat, the more an AC unit will have an easy time cooling it down. Even such small measures as the ones mentioned above can transform an oven of a garage into a place that can be cooled by an AC decently.

Power Supply and Electrical Requirements

In the process of installing an air conditioner in your garage, you should not forget the electrical aspect. Air conditioners and particularly the larger ones consume a lot of current. The following are what to remember:

• Outlet and Circuit Capacity: Check what else is on the circuit that you plan to use for the AC. A small 8,000 BTU portable AC might draw around 6-8 amps, while a 14,000 BTU portable can draw 10-12 amps at full tilt. Standard garage circuits are often 15 amps. If that circuit also has the garage lights and maybe a fridge or power tools running, you could trip the breaker. Ideally, dedicate a circuit to the AC (or ensure nothing else heavy is running simultaneously). If needed, have an electrician install a new circuit/outlet for the AC, particularly for through-wall or mini-split units that are higher BTU.
• 115V vs 230V: Most portable ACs and window units up to about 12,000 BTU run on standard 115/120V. Some in the 12,000-15,000 BTU range (especially older models) and many 18,000+ BTU units require 230V. Mini-splits of 12k BTU are available in both 115V and 230V variants (115V models are convenient for garages without a 230V line, though 230V models might be slightly more efficient for the bigger sizes). Through-the-wall units often come in both versions depending on BTU – for example, 10k BTU might be 115V, but a 14k BTU through-wall likely needs 230V. Check the unit’s specs before buying. If it’s 230V and you don’t have a suitable outlet, you’ll need an electrician to install one from your breaker panel (and have capacity for the additional 230V breaker).
• Extension Cords: It’s generally not recommended to use extension cords with air conditioners because of the sustained high current draw (this can cause voltage drop or overheating in undersized cords). If you must use one temporarily, use a heavy-duty extension cord rated for AC use – it should be a low-gauge (like 14 AWG or thicker, 12 AWG for bigger units) and as short as possible. For a permanent setup, it’s safer to add an outlet closer to the unit.
• Startup Surge: Remember that compressors draw more startup current (locked-rotor amperage) when they start up, a second or two. That is why lights may flicker as an AC is started. You may not be aware of flicker in a garage circuit, but the surge may cause a breaker to trip when the margin is narrow. Units driven by inverters (such as the Dreo and Midea portables, or most mini-splits) have gentler start characteristics that reduce this effect, but the more basic on/off units have sharper surges.

Having enough power to your house does not only help you avoid the irritating breaker trips, it is also a safety concern, overheated wiring can cause a fire. Therefore, make sure that the circuit amperage, what is on it, and the requirements of the AC are checked twice before you plug in your new AC.

To be on the safe side, ask an electrician when you are not sure. Most garages can support such additions, although an older house or a circuit that is already carrying a lot of loads will require an upgrade.

Additional Tips for Cooling a Garage Efficiently

In addition to the AC unit itself, a couple of additional tips and tricks are available to maximize cooling your garage:

• Pre-Cool if Possible: If you know you’ll be working in the garage, turn on the AC a little ahead of time. Garages often have a lot of thermal mass (concrete floors, tools, cars) that store heat. It can take time for everything to cool down. By starting the AC 30 minutes or an hour before use (perhaps via smart Wi-Fi control or a timer), you can have the space at a comfortable temperature when you arrive, rather than waiting in the heat for it to cool.
• Use Fans to Circulate Air: In a larger garage, an AC unit will create cool air but might only do so in one corner. Using a simple oscillating fan or box fan can help spread the cool air around and eliminate hot pockets. For example, you could place a fan near the AC output to push cool air toward the back of the garage. If you have high ceilings, a ceiling fan or high-mounted fan can help destratify the air (hot air tends to collect up high otherwise).
• Mind the Garage Door Usage: Try to minimize how often and how long you open the big garage door during the hottest parts of the day, as this will let all the cool air rush out and hot air flood in. If you need ventilation for fumes (say, running a vehicle briefly or painting), do that, but you’ll need to give the AC time to recover once you close up again. You might even point a fan blowing out during that time to direct hot air or exhaust out faster, so the door doesn’t stay open as long.
• LED Lighting: This is a small thing, but if you have older incandescent or halogen work lights in the garage, they emit a lot of heat. Switching to LED bulbs or fixtures reduces the heat load. Every bit counts when you’re fighting the heat in a garage.
• Keep Your AC clean: A well-serviced AC is more efficient. In portables and through-wall units, clean or change the air filter frequently (airflow and cooling capacity are reduced by a clogged filter). In evaporative coolers, make sure that the pads are clean and change them according to the recommendation. Mini-splits are also equipped with washable filters and at times require the coils to be cleaned of dust. And make sure that the air around any air intake (on portables, typically the back of the unit) is clear so that it does not get blocked by anything.

With these practices coupled with a good air conditioning unit, you will be able to make your windowless garage a lot cooler and comfortable even in the hottest days of summer. A cool environment will make the world of difference whether you want to work on your car, have hobbies or have a home gym in the garage.

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