A homeowner peers under the opening of his garage door and smiles as he opens it from inside

Perhaps your garage has some insulation, but not enough to prevent it from becoming scorching hot in the summer and freezing in the winter. You’d love a more efficient heating and cooling solution for this space than what you have at current.

Is a mini-split heat pump the correct answer?

Today’s article will tell you everything you need to know about using mini-splits in your garage. Then, we’ll discuss the benefits of a mini-split system and help you find the perfect unit for your garage size. 

Let’s get started! 

Is Using a Mini-Split in Your Garage a Good Idea? 

Yes, mini-split HVAC systems are great for garage installations. They require no ductwork, operate extremely efficiently and quiet, and can be left on all the time. You can calculate the exact size you need for your space. An average-sized 400-square-foot garage would need 6,000 BTUs of heating and cooling.

What Are the Benefits of a Mini-Split for the Garage?

Are you tired of being frozen or sweated out of your garage each time you spend more than 15 minutes there? Then, add an HVAC solution like a ductless mini-split system instead of paying to get the entire space insulated (or re-insulated).

Here are the would-be advantages of that decision.

All Components Are Relatively Close

A ductless mini-split system is comprised of at least one indoor air-handling unit, one compressor, and wiring between the two.

Many homeowners who choose mini-split systems will decide to get the compressor installed in their backyards. It should have its own concrete slab (you can pour this before installation) and, ideally, overhead protection such as an awning.

The outdoor compressor component of a ductless mini-split

More than likely, the distance between the compressor and the indoor air-handling units in your garage isn’t that far, which can be beneficial in several ways.

For one, your mini split setup will require less length of wire to install, which can shave off some of the installation costs.

 It’s also easier for a mini-split technician to access both parts of the system when they come to your home for routine mini split maintenance. 

No Need for Duct Installation

Let’s be honest—ducts aren’t appealing, yet they’re required for most heating and cooling options.

Getting ductwork installed in or around your garage would detract from the look of this home attachment and possibly reduce your property’s curb appeal.  

A ductless mini-split system, by comparison, is much less unsightly. These days, you have methods for hiding or minimizing the indoor air-handling units so your garage can maintain whatever look you’re going for. 

Preservation of Items Stored Items

What do you use your garage for? 

According to a 2013 Home Innovation Research Labs study, 74% of respondents said they used the garage for parking their car. Another 15% used the garage for storage, and three percent utilized it as a workspace.

Well, for those who opt to use their garages for storage, what you’re storing there is very important.

Interior view of a garage from the open door and all the items stored inside

 For instance, you’re usually told not to put these items in your garage:

  • Toys (bugs and pests can destroy them)
  • Electronics (the cold or heat can short them out for good)
  • Clothing (moths can eat them)
  • Carpets and rugs (pests can move in and lay eggs)
  • Wood (doesn’t do well in changing temperatures)
  • Books (moisture will damage them)
  • Photographs (same thing; moisture damage)
  • Pet food (rats might eat it)
  • Propane (risks a gas leak from changing temperatures)
  • Paint cans (in high heat, the pain can separate)
  • Canned food (expiry occurs faster)

As this list shows, the fluctuating heat and cold can wreck a lot of these everyday items.

Once you have a ductless mini-split system in your garage, you can resume using the space for storage if that’s what you usually do. 

Your items should stay unharmed even if you store them in the garage for a while! (Except for food, of course.)

Affords the Ability for Garage Recreation 

The survey above said that only three percent of people use their garage as a workspace, but maybe that’s only because most garages are too hot or cold to use for much.

That doesn’t have to be the case for your garage. With a ductless mini-split system, you can keep the garage at a cozy temperature all year long. Perhaps it becomes a man cave or she-shed, a workshop, a place for band practice, or just a lounge area—it’s your choice! 

What Size Mini-Split Do You Need for a Garage?

Whether yours is a small single-car garage or a sizable four-car garage, a mini-split heat pump is still a viable HVAC solution. 

The only question is just what size mini-split you need. To answer that question, you need to measure the square footage of your garage (if you don’t already know it).

This handy chart can determine how much heating and cooling power you require:

Size of Your Garage Heating and Cooling Required 
200 square feet3,000 to 5,000 BTUs
300 square feet4,500 to 7,500 BTUs
400 square feet6,000 to 10,000 BTUs
500 square feet7,500 to 12,500 BTUs
600 square feet9,000 to 15,000 BTUs
700 square feet10,500 to 17,500 BTUs
800 square feet12,000 to 20,000 BTUs
900 square feet13,500 to 22,500 BTUs
1,000 square feet15,000 to 25,000 BTUs

The above amount of heating and cooling power is presented as a range because how many BTUs your garage will require depends on the brand of mini-split you buy and its SEER and HSPF rating(more to come on that shortly!).

The chart above also assumes that you’re using one indoor air-handling unit for the entire space.

A ductless mini-split in the corner of a room below the ceiling

As discussed extensively on the blog, mini-splits are dividable into zones. A zone can be one room or different parts of a room.  You could split your garage into two or more zones depending on its size and how disparate the heating and cooling requirements are across the garage.

For example, if you work in the back of the garage, you might be nice and comfy, but at the front is the drafty old door. This part of the garage is cooler in the winter and warmer in the summer.

Likewise, perhaps your garage has a couple of large side windows. In the summer, this part gets especially hot.

You could split your garage in half or even three ways if you have a window and a drafty garage door.

Let’s say, for example, your garage is a very generously sized 900 square feet. You’d typically need a mini-split system with a cooling and heating capacity between 13,500 and 22,500 BTUs.

By splitting that three ways, now each zone is 300 square feet. So you’d need about 4,500 BTUs of heating and cooling per zone. 

What SEER and HSPF Ratings Should Your Mini-Split Have?

Ductless mini-splits are lauded for their energy efficiency compared to traditional HVAC units like furnaces or air conditioners. On average, mini-splits are 30% more energy-efficient and can be upwards of 50-60% in some cases. 

To ensure your mini-split is as energy-efficient as it gets, you should pay attention to both the SEER and HSPF as you shop around.  

Let’s explain what both these acronyms mean and why they’re critical. 

SEER Rating

First is SEER, which is short for the seasonal energy efficiency ratio. The term SEER was coined by the Air Conditioning, Heating, and Refrigeration Institute in its 2008 standards. 

SEER measures how much cooling output a mini-split uses on an average day of cooling. To calculate the SEER, you divide that cooling output by how much electricity the mini-split needs.

A higher SEER rating means the unit is more energy-efficient, whereas a lower number indicates it is worse for our planet and your monthly utility bill.

In January 2016, the US federal government mandated that all new mini-split heat pumps had a SEER rating of at least 15, but that’s considered very outdated by today’s standards. 

If yours is an Energy Star-rated mini-split, its SEER will be anywhere from 20 to 25. As of this writing, 25 is the highest SEER rating, but we’re sure that will change with time. 

Your new garage mini-split needn’t have a rating of 25, but you don’t want it to be under 20. If so, it won’t be as energy efficient as it could be. 

HSPF Rating

As we recently wrote, a ductless mini-split system can work as both a heat pump and an air conditioner. 

Thus, while SEER is concerned with how energy-efficient a mini-split is while it’s cooling, there’s also a rating that determines the energy efficiency of a mini-split as it’s heating. That’s the heating seasonal performance factor or HSPF. 

HSPF compares the heat output ratio in BTUs versus the amount of electricity the mini-split uses, calculated in watt-hours. You divide the two numbers like you would when calculating SEER.

The rating is pretty different, though. While a SEER of eight would be way too low, anything rated eight or above in the world of HSPF is considered very energy-efficient.

These units are usually eligible for a US Energy Tax Credit. Plus, once a heat pump has an HSPF of 8.2 or over, it’s an Energy Star-approved appliance. 

The highest HSPF rating as of this writing is 10. As with SEER ratings, your mini-split needn’t have an HSPF of 10, but you want the score to be at least an eight. 


Adding mini-splits to your garage is a great way to use this space to its full potential. The garage will feel comfortable regardless of the weather outside, so you can work on restoring an old car, enjoying some hobbies, or simply using it for storage!

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