Cooling a Bonus Room Over the Garage with a Mini Split.
Updated September 2026
Builders often treat bonus rooms over garages as an afterthought, running a single thin duct that leaves the space 10-15 degrees hotter than the rest of the house. A ductless mini split can fix that without tearing into walls or upgrading the entire HVAC system.
Flat pricing, same everywhere we work
| System | Flat price, installed | Included |
|---|---|---|
| One split (single room) | $1,500 | Indoor head, outdoor condenser, line set, standard electrical, all labor |
| Two splits | $2,500 | Everything above, two zones |
| Three splits | $3,500 | Everything above, three zones |
Every install is wired to code by our TDLR-licensed contractor. Long line-set runs, panel upgrades or unusual mounting can add cost, and we tell you up front, before any work starts. For market context, see our Austin mini split cost guide: typical Central Texas quotes run $3,000 to $5,000 for a single zone.
Why Bonus Rooms Over Garages Run Hotter
The problem starts with how these rooms are framed. Most builders run one small supply duct off the main trunk line, sized for a bedroom rather than a larger bonus space. The duct is often routed through an unconditioned attic or garage, where summer heat soaks into the air before it even reaches the room. Insulation is usually minimal, and the garage door below acts like a radiator, transferring heat upward.
Adding a second duct or upsizing the existing one would require opening walls and possibly upgrading the main HVAC system, which can cost thousands. A mini split avoids that by delivering cooled air directly to the room. Our flat-rate installs for one zone start at $1,500, including the outdoor condenser, indoor head unit, line set, and electrical hookup. No surprises, no in-home quote required.
How a Mini Split Solves the Problem Without Major Work
The indoor unit mounts high on the wall, typically opposite the garage door to counteract rising heat. A small hole, about three inches wide, is drilled through the wall for the line set, which connects to the outdoor condenser. The system runs on its own circuit, so it doesn’t overload the existing ductwork or require a panel upgrade unless the home already needs one. Most installs finish in a single day.
Our TDLR-licensed contractors handle everything from mounting the unit to testing the system before leaving. The flat price includes labor, materials, and even a Home Depot run for touch-up paint if needed. If the line set needs to run more than 25 feet or the wall requires special mounting, we’ll tell you upfront. No hidden fees, no last-minute upsells.
Questions
Will a mini split cool the bonus room as well as the rest of the house?
Yes. A properly sized mini split will match the temperature of the rest of the house, even in 100-degree Central Texas heat. The key is placing the indoor unit where it can distribute air effectively, usually high on the wall opposite the garage door.
Can I add a mini split if my electrical panel is already full?
If your panel is full, we’ll let you know before starting work. A panel upgrade isn’t included in the flat price, but we can install the mini split once the upgrade is complete by a licensed electrician.
Does the outdoor unit need to sit right below the bonus room?
Not necessarily. The line set can run up to 50 feet, so the outdoor unit can be placed on the side of the house, the roof, or even the garage wall if space allows. We’ll assess the best location during the initial visit.
We install across Central Texas. See the Austin mini split cost guide, full Central Texas service area or Austin mini split installation.
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