If you are thinking about cooling or heating your garage, you might be wondering what size mini split you need. Sizing is not just about square footage. It is about how the space is built, how it is used, and what the weather does here in Central Texas.
If you are thinking about cooling or heating your garage, you might be wondering what size mini split you need. Sizing is not just about square footage. It is about how the space is built, how it is used, and what the weather does here in Central Texas.
This guide will walk you through the basic math and the real world factors that matter for a garage installation. At Jester Climate we keep our pricing simple: a flat rate of $2,400 for standard install, with a $400 deposit to hold your day and the rest due on completion. So you can focus on getting the right size, not on hidden fees.
A common rule of thumb for cooling is about 20 to 25 BTUs per square foot in our climate. But that number assumes average insulation and normal ceiling height. For a 400 square foot garage with decent insulation and an 8 foot ceiling, that would land around 8,000 to 10,000 BTUs. But most garages are not well insulated. They have thin walls, uninsulated garage doors, and often no ceiling insulation above the attic space. If your garage is poorly insulated, you might need 30 to 35 BTUs per square foot or more.
To get a rough idea, measure the length and width of the garage floor, then multiply for square footage. Then look at your walls: are they finished with drywall and insulation or just bare studs? What about the ceiling? If there is an attic above, is the garage ceiling insulated? What about the garage door? A single layer metal door with no insulation lets in a lot of heat. You can upgrade to an insulated door or add a reflective barrier. The better the insulation, the smaller the mini split you can get away with. This keeps upfront cost lower and saves energy over time.
How you will use the garage matters a lot for sizing. If you are just parking cars and storing boxes, you might only need to knock the edge off the heat so tools and paint don't suffer. A 9,000 BTU unit could be enough for a two car garage in that case. But if you plan to work out, do woodworking, or use power tools, you generate extra heat yourself. And you want the space comfortable enough to stay in for hours. That often means sizing up by one step, for example from 9,000 to 12,000 BTUs.
Also think about how often you will run the system. If it is occasional use, an undersized unit might struggle to catch up on a 105 degree Austin afternoon. Oversizing is also a risk because a unit that cycles on and off too quickly does not remove humidity well. Humidity control is important in our muggy summers. A properly sized unit runs longer cycles and leaves the air feeling drier and more comfortable.
In Central Texas we care about cooling most of the year, but garages can get very cold in winter, especially if they are detached or have no insulation. A mini split with a heat pump can handle both. Sizing for heating follows a similar logic but uses different BTUs per square foot because heating needs are less extreme here than in northern states. For a typical garage, heating capacity is usually not the limiting factor. The cooling load drives the size.
One hidden factor is the attic above the garage. If your garage has an open attic or the ceiling is uninsulated, the hot air from the attic will push heat down into the garage. This can easily add 20% to the cooling load. Sealing air leaks and adding insulation between the garage and attic is one of the most cost effective ways to reduce the size you need. If that is not an option, plan for a larger unit. A quick test: place your hand on the garage ceiling on a hot afternoon. If it is hot to the touch, you are losing that heat into the room.
Permit requirements vary by city. In Austin, Round Rock, and other Central Texas towns, an electrical permit is often needed if you run a new circuit. The installer handles what is required for your location. We include permit work in our flat rate when needed so you do not have to worry about it.
With average insulation and a standard garage door, you likely need a 12,000 BTU unit for cooling. If the garage is well insulated with an insulated door and sealed attic, a 9,000 BTU might work. If it is poorly insulated, you may need 15,000 BTUs. Use the square footage and insulation factors we described to narrow it down, and we can confirm on a site visit.
A window unit is cheaper upfront and easier to install yourself. But it takes up window space, can be noisy, and often does not heat well. A mini split is quieter, leaves the window free, provides both heating and cooling, and can be mounted high on the wall to save floor space. For a garage you use regularly, the comfort and convenience of a mini split is usually worth the higher upfront cost. If you rarely use the garage, a window unit might be the practical choice.
Yes, but the unit will have to work harder to keep up. Without ceiling insulation, the heat from the attic radiates into the garage. You may need to go up one size from what you would choose for a well insulated garage. Adding insulation to the garage ceiling later is a good upgrade because it improves efficiency and comfort significantly.
Each week we set aside one day as Joker Day. The price for a standard installation on that day is lower than our regular $2,400 flat rate. The exact Joker price changes weekly and is shown on our homepage. You can book a regular day at the standard rate any time, or check the homepage to see if the Joker price works for your schedule.
Ready to get the right size for your garage? Call Jester Climate at (512) 297-7493 or book online with a simple $400 deposit and pay the rest when the system is running.