WA Lic. INFINHA841B8 400+ Google reviews
Quick answer
- A mini-split avoids the cost and disruption of extending existing ductwork into a new addition or converted space.
- One outdoor unit can serve multiple indoor heads (multi-zone) if you're planning more than one new space, not just this one.
- Detached garages and shops need their own properly sized electrical circuit for the mini-split — that's part of the install, not an afterthought.
- Sizing by square footage alone is the most common mistake; insulation level, garage door area, and how the space will actually be used all change the load.
Why ductless is the default here
Extending ducts into an addition or garage usually means running new supply and return through finished walls, ceilings, or a slab — expensive and invasive. A ductless system needs only a small line-set penetration through an exterior wall.
Garages and shops have their own rules
Uninsulated garage doors, concrete slab floors, and intermittent use — heating a cold shop back up rather than holding a steady temperature in a living space — all change sizing and equipment choice compared to a standard bedroom addition.
Single-zone vs. multi-zone
If this is the only space you're adding, single-zone is simpler and often more efficient per head. If you're planning a shop plus a bonus room, or a full ADU, a multi-zone outdoor unit — like the Hisense Hi-MULTI line — can serve several heads from one outdoor unit.
What the install actually involves
An electrical capacity check, condensate routing, mounting placement for both indoor and outdoor components, and sizing correct for the specific space's insulation and use — not a generic 'one ton per so-many square feet' rule.
Where this decision goes wrong
Sizing off square footage alone
A mini-split sized purely by the room's square footage — without accounting for an uninsulated garage door, vaulted ceiling, or slab floor — either short-cycles from being oversized or never quite catches up from being undersized.
Skipping the electrical assessment
Assuming the existing garage outlet or panel capacity can support a mini-split's dedicated circuit without checking first turns a straightforward install into a mid-project change order.
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Family owned · WA Lic. INFINHA841B8 · 400+ Google reviews
Common questions
Can a mini-split heat a detached garage or shop through winter?
Yes, with correct sizing for the space's insulation and intended use. A cold-climate model keeps producing heat well below freezing, which matters for an unheated shop starting from a cold soak.
Do I need a permit to add a mini-split to a garage?
Typically yes for the mechanical and electrical work — we pull the permit as part of the install so you don't have to track it down yourself.
How many indoor heads can one outdoor unit support?
Multi-zone outdoor units support multiple heads, with the exact number depending on the model. We size the outdoor unit to the combined load of every space it'll serve — current and planned — not just what's needed today.
Will a mini-split work well in an uninsulated garage?
It'll run, but uninsulated garage doors and walls make it work much harder and cost more to condition. We usually recommend at least some insulation upgrade alongside the mini-split for a garage you'll actually use as living or shop space.
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Infinity Heating & Air — licensed WA HVAC contractor (Lic. INFINHA841B8), family-owned in Graham. Last updated 2026-07-14.