Short answer: a ductless mini-split is a heat pump with a small outdoor unit and one or more wall-mounted indoor units, connected by a thin line set. A single-zone system typically costs about $3,000 to $4,900 installed, and multi-zone systems about $4,200 to $7,900 for the same capacity, according to Inch Calculator. They make the most sense in homes without ducts, additions, and rooms that are always too hot or too cold.
How a mini-split works
Like any heat pump, it moves heat instead of making it: outdoors to indoors in winter, indoors to outdoors in summer. Each indoor unit has its own thermostat, so every room (zone) is controlled separately. Because there are no ducts, there are no duct losses.
When a mini-split is the right choice
- No ductwork: older homes heated by boilers, baseboards or wood stoves.
- Additions, attics, garages and sunrooms where extending ducts is impractical.
- Replacing electric baseboard heat, where a heat pump can cut heating electricity by about half (energy.gov). See heat pump vs baseboard.
- Problem rooms that the central system can’t keep comfortable.
- Zoning: heating only occupied areas can save more than 20% compared with heating the whole house, per the DOE.
When it isn’t
- You already have good ducts: a ducted heat pump usually costs less per room.
- Many small rooms: one head per room adds up fast, and undersized heads in closed rooms leave other rooms cold.
- You dislike the look of wall units (ceiling cassettes and slim ducted units exist, at a higher price).
Single-zone vs multi-zone
| Several single-zone systems | One multi-zone system | |
|---|---|---|
| Outdoor units | One per room | One for several rooms |
| Efficiency | Usually higher; each unit sized for its room | Can be lower if heads are oversized for their rooms |
| If the outdoor unit fails | Only one room loses heat | All connected rooms lose heat |
| Space and looks | More outdoor units | Fewer outdoor units |
What to ask installers
- Heating capacity at 5°F (and 17°F) for cold climates, not just the nominal rating. See heat pumps in cold climates.
- HSPF2 and SEER2 ratings for each indoor/outdoor combination.
- A room-by-room load calculation, so each head is sized right.
- Where the line set and condensate drain will run, and how they’ll be covered.
- Whether the outdoor unit will sit on a stand above snow level.
- Labor warranty length.
Running tips
- Clean the washable indoor filters every month or two.
- Leave heads at steady settings rather than switching them off and on.
- Keep the outdoor unit clear of snow and leaves.
FAQ
Can one mini-split heat a whole house? In small, open, well-insulated homes, sometimes. Most homes need more than one head for even comfort.
DIY kits? Pre-charged kits exist, but warranties often require professional installation, and electrical work may need a permit. Compare full installation prices in heat pump installation cost.