Whether you’re upgrading your garage to a full-blown workshop or home gym or simply want a more comfortable space to work on projects, installing a ductless mini split air conditioner is one of the smartest solutions for efficient, targeted cooling. But before you buy, there’s a crucial step you cannot skip, proper sizing. So how do you size a mini split AC for your garage?
At Galmiche & Sons, we’ve helped hundreds of homeowners in the St. Louis area find the perfect HVAC solution for every space in their home, including utility areas like garages. In this guide, we break down how to size a mini split AC for a garage or workshop, helping you avoid costly mistakes and get the comfort you deserve.
To learn more about air conditioner sizing and request a quote for your new HVAC system, contact our St. Louis HVAC experts today.
Why Mini Split ACs Are Ideal for Garages and Workshops
Traditional central air systems typically don’t extend into garages, and window units aren’t always a practical or effective choice. A ductless mini split system offers flexible, energy-efficient cooling without the need for ductwork. They’re compact, quiet, and easy to zone, making them perfect for single spaces like:
- 1-car or 2-car garages
- Detached workshops
- Converted studios or home gyms
- Hobby or crafting spaces
But even the best mini split system will underperform if it’s not correctly sized for the space.
Not sure if a ductless mini split is right for you? Learn more tips to cool your garage.
Factors to Consider When Sizing a Mini Split for Your Garage
Sizing a mini split ac for your garage isn’t just about square footage. Garages are unique environments with characteristics that dramatically affect how much cooling power you’ll need.
1. Square Footage
Start by measuring the length and width of your garage. Multiply to get the total square footage. A standard 1-car garage is about 200–300 sq. ft., while a 2-car garage can range from 400–600 sq. ft.
2. Ceiling Height
Higher ceilings mean more air volume, which requires additional BTUs. Be sure to factor in ceiling height if it exceeds the standard 8 feet.
3. Insulation Quality
Garages are often poorly insulated. Uninsulated walls or garage doors allow heat to enter and escape quickly, meaning you’ll need a more powerful unit. If you haven’t upgraded insulation, consider it before installation to reduce your BTU needs.
4. Sun Exposure
Does your garage face west and bake in the afternoon sun? Does it have windows? Sun exposure and heat gain from concrete floors or metal doors will require higher capacity to keep the space cool.
5. Appliances and Equipment
If your workshop includes power tools, compressors, or even a refrigerator, these generate heat and should be considered when calculating BTU needs.
BTU Guidelines for Garages and Workshops
Here are rough BTU estimates for garage mini splits based on common sizes and usage:
| Garage Size | BTU Estimate|
| 200–300 sq. ft. (1-car, insulated) | 6,000–9,000 BTU |
| 400–600 sq. ft. (2-car, insulated) | 12,000–18,000 BTU |
| 600+ sq. ft. (workshop, uninsulated) | 18,000–24,000 BTU |
These are general ranges. For accurate results, Galmiche & Sons performs a load calculation to match your unique space to the right system.
FAQs: Mini Split Sizing for Garages
If your garage is drafty or subject to extreme temperature swings, we recommend insulating walls and garage doors first. It will improve efficiency and reduce the size of the system needed.
Not always. Garages tend to have more heat gain and lack insulation, meaning they often require more BTUs for the same square footage.
An undersized unit will run constantly without achieving comfort. An oversized unit may short cycle, wearing out faster and failing to manage humidity effectively.
Get the Right-Sized Mini Split for Your St. Louis Garage
Don’t let discomfort ruin your workspace. Whether you’re building a home gym, creating a woodworking shop, or just want a cool garage for summer, Galmiche & Sons is here to help.
With decades of experience serving homeowners throughout St. Louis, we specialize in ductless mini split air conditioner installation and custom sizing consultations. We’ll evaluate your garage, consider all performance factors, and recommend a properly sized unit that keeps your space cool and efficient.
Contact Galmiche & Sons today to schedule a free consultation and get the expert help you need to size and install the perfect mini split system for your garage or workshop.
