A ductless mini-split moves refrigerant from an outdoor unit to one or more indoor units through a pair of copper lines, and each indoor unit has its own fan, coil and setting. In San Jose it solves problems that central air handles badly: an older Willow Glen or Rose Garden house with no ducts and woodwork worth protecting, a garage turned into an office, a room addition the original system was never sized for, or a bedroom over the garage that stays hot until midnight.
Where a mini-split makes sense
- No existing ductwork. New ducts in an older house mean opening ceilings and closets. A mini-split needs a wall opening about three inches across for each indoor unit.
- Room additions and converted garages. Stretching old ducts to a new room rarely works well, and a garage office or workshop usually has no ducts at all.
- Hot and cold spots. A west-facing room, an upstairs bedroom or a sunroom can get its own unit while the central system keeps the rest of the house.
- Home offices. Cool the room you work in during the day without cooling the whole house.
- The far end of a large home. In bigger Almaden Valley houses, a wing at the end of long duct runs can be easier to fix with one ductless unit than with more ductwork.
Most mini-splits are heat pumps, so the same unit heats on cool winter nights. Their inverter compressors speed up and slow down to match the room instead of cycling on and off, which keeps them efficient and quiet, and with no ducts there are no losses through a hot attic.
Single-zone or multi-zone
| Setup | Fits | Keep in mind |
|---|---|---|
| One outdoor unit, one indoor unit | A single room, addition or garage office | Simplest layout and the lowest cost |
| One outdoor unit, several indoor units | A few rooms in a house without ducts | One outdoor unit to place; indoor units usually share heating or cooling mode |
| Several single-zone systems | Rooms with very different loads or schedules | More outdoor units, but each room runs on its own |
Choosing the indoor units
- Wall-mounted units are the most common and least expensive. They go high on a wall, ideally an outside one.
- Ceiling cassettes sit flush in the ceiling and need space above, which a single-story house with an attic usually has.
- Floor consoles fit low under a window and suit rooms used mainly for heating.
- Concealed ducted units hide in an attic or closet and serve one or two rooms through short ducts, so only grilles show.
Sizing room by room
Each indoor unit is sized for its own room, not for the house. A west-facing room with big windows on a hot valley afternoon needs more capacity than its floor area suggests; a shaded north bedroom needs less. An oversized unit cycles on and off and leaves the room clammy, while an undersized one runs flat out and still loses ground in July. The load for each room is worked out before any unit is chosen.
Placement, lines and drains
The outdoor unit sits on a ground pad or a wall bracket with room for air to flow and for service. Many San Jose side yards are narrow, and a unit squeezed into a tight, sun-baked spot breathes its own hot air, so placement is planned, not improvised. Noise near bedroom windows, yours or a neighbor’s, is part of that decision.
Lines take the shortest neat route: outside under a cover, or through the attic or crawlspace of an older house to avoid cutting finishes. Lines that pass through a hot attic need intact insulation. Each indoor unit also needs a drain, by gravity to the outside where possible or with a small condensate pump where not.
Before any refrigerant is released, flare joints are tightened to specification and the lines are pressure tested and pulled into a deep vacuum. Careful work here prevents slow leaks at the joints, a common cause of early mini-split trouble.
Power: check the panel first
The outdoor unit needs its own circuit, usually 240 volts, and a disconnect beside it. Older homes in Cambrian and Willow Glen often have small or full panels, and a multi-zone system draws more than a single-room unit. Panel space and capacity are checked during the free estimate. If an electrician needs to upgrade the panel, you know before you commit.
What moves the price
Most ductless installations fall between $3,000 and $15,000. A single wall-mounted unit in one room sits at the low end. The price rises with the number of indoor units, ceiling or concealed units, long or awkward line routes, condensate pumps and electrical work. The mini-split installation cost guide goes further, and our comparisons of Fujitsu and Mitsubishi and Daikin and Mitsubishi cover two common brand questions.
For homes in North San Jose, see mini-split installation in North San Jose. If you would rather heat and cool the whole house through existing ducts, compare a central heat pump. Already have a ductless system that is acting up? See mini-split repair.