What Size Mini Split for a Garage?
What size mini-split heats and cools a garage — why an uninsulated garage needs more BTU than living space, the size by garage type, and the units that fit.
Prices vary by location. Verify with local suppliers.
What size mini split for a garage
A garage isn’t a living room — an uninsulated door, bare walls and sun on the roof all add heat load — so you size up from the raw floor area. Set the calculator above to poor insulation to see the effect. As a starting point by garage type:
| Garage | Approx. size | Recommended BTU |
|---|---|---|
| 1-car | ~250–300 sq ft | 9,000–12,000 BTU |
| 2-car | ~400–500 sq ft | 18,000 BTU (most common) |
| 3-car | ~600–750 sq ft | 18,000–24,000 BTU |
Insulation is the big variable
For an uninsulated or hot-climate garage, add roughly 30–50% BTU over the room-size baseline — or better, insulate the walls, ceiling and door first so a smaller, cheaper unit can keep up. A heat-pump mini-split both cools and heats, which makes it ideal for a year-round garage gym or workshop; size up if you run heat-generating equipment.
See the size classes: 12k (1-car) · 18k (2-car) · 24k (3-car). For a DIY install, the best DIY mini-splits skip the vacuum pump.
Frequently asked questions
What size mini split do I need for a 2-car garage?
An 18,000 BTU mini-split is the most common and reliable choice for an average, reasonably sealed 2-car garage (about 400–500 sq ft). Garages carry more heat load than living space — an uninsulated door, uninsulated walls and sun on the roof — so you size up from the raw floor area rather than treating it like a room.
Is 12,000 BTU enough for a garage?
For a small, attached, reasonably sealed 1-car garage, yes. For a 2-car or an uninsulated garage a 12k unit usually falls short — 18,000 BTU is the safer standard. The calculator’s “poor insulation” setting shows how much a bare, uninsulated garage adds to the load.
Can you use a mini split in an uninsulated garage?
Yes, but you should upsize the BTU by roughly 30–50% over the room-size baseline and expect higher running costs. Insulating the walls, ceiling and garage door first dramatically improves performance and lets a smaller, cheaper unit keep up — it’s usually worth doing before you size the system.
What size mini split for a 3-car or 700 sq ft garage?
A 3-car or roughly 700 sq ft garage generally needs 18,000–24,000 BTU depending on insulation and climate; a poorly insulated 700 sq ft garage in a hot region leans to 24,000. For a garage gym or workshop with heat-generating equipment, size up rather than down.