HVAC · Service

Mini split installation, zone by zone

Ductless heating and cooling for rooms the ducts never reached. What it costs per zone, where the DIY kits genuinely work, and the point where you should be pricing central air instead.

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In short

What is mini split installation?

A mini split is a ductless heat pump: an outdoor compressor connected by a slim refrigerant line set to one or more wall, ceiling or floor units inside. Each indoor head is its own zone with its own thermostat. A single-zone install is typically a half day to a day; multi-zone systems take longer because every head needs its own line run back to the outdoor unit.

Triggers

Signs you need mini split installation

You have a room the ducted system has never reached — a bonus room over the garage, a finished attic, a sunroom
You are converting a garage, basement or outbuilding and extending the existing ductwork is impractical
The house has no ductwork at all — hydronic baseboard, radiators, or electric resistance heat
One or two rooms are consistently much hotter or colder than the rest and balancing the ducts has not fixed it
You are running window units or portable ACs and want something quieter, more efficient and permanent
Someone in the house wants a different temperature to everyone else, and the thermostat war is real
You want to heat and cool a home office or workshop without conditioning the whole building to do it

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The job

How mini split installation actually works

Room-by-room load calculation

Each zone gets sized on its own, not on floor area. A south-facing sunroom with a lot of glass and a shaded interior bedroom of the same size need very different capacities.

Watch for: Sizing from a chart of square footage to BTU. Oversized mini split heads are worse than oversized ducted systems: an inverter compressor already modulates down, and a head that is too large for its room will sit at minimum output, cycle, and never dehumidify properly.
Single zone or multi zone

A single-zone system pairs one outdoor unit with one head. A multi-zone runs several heads from one outdoor unit. Multi-zone is tidier outside and shares one condenser; single zones are cheaper per unit, fail independently, and often modulate better.

Watch for: A multi-zone sold purely because it is one box outside. If one head is running and the others are off, some multi-zone systems run inefficiently at very low load. For two zones far apart in a house, two single-zone systems are frequently the better engineering answer.
Indoor head placement

Wall units usually go high on an interior or exterior wall with clear space around them and a straight path for the line set to leave the building. Ceiling cassettes and floor-mounted units exist for rooms where a high wall unit is impractical or unwelcome.

Watch for: A head placed where the line set is easiest to run rather than where the air needs to go. Blowing across a doorway, straight at a bed, or into a wardrobe alcove is a comfort complaint you will live with for fifteen years to save an afternoon of routing.
Outdoor unit siting

The condenser needs clearance for airflow, a level mounting pad or wall bracket, and somewhere that its noise and its winter defrost water are not a problem. In cold climates it is raised above expected snow depth on a stand.

Watch for: A condenser under a bedroom window or hard against a neighbour's boundary. It runs at night in summer. Also watch for units set at ground level in snow country — a heat pump that drifts over stops working when you need it most.
Line set routing and the wall penetration

A three-inch hole through the wall carries the refrigerant lines, condensate drain and control wiring. Outside they run in a line-hide cover to the condenser. Shorter and straighter runs perform better and cost less.

Watch for: Bare, untidy line sets taped to the exterior. It is not just cosmetic — unprotected insulation degrades in UV and the performance goes with it. Also make sure the condensate line falls continuously; a head that has to drain uphill needs a condensate pump, and that should be quoted, not improvised.
Electrical supply

Most systems need a dedicated circuit and a disconnect at the outdoor unit. Multi-zone systems and larger single zones frequently need 240V, which in an older house can mean panel work.

Watch for: The panel checked on install day rather than at the site visit. This is the most common cause of a mini split job stopping halfway through with the wall already drilled.
Evacuation, charge and commissioning

Lines are pressure-tested with nitrogen, evacuated to a deep vacuum, then the factory charge in the condenser is released. Longer runs need additional refrigerant added by weight to the manufacturer's specification.

Watch for: The extra charge for a long line run being skipped. It is a documented number in the installation manual, it is measured with scales, and omitting it quietly costs you capacity for the life of the system.

Money

What does mini split installation cost?

A single-zone mini split installed typically runs $3,000 to $6,000, with each additional zone adding a few thousand more. Line run length, whether a condensate pump or electrical work is needed, and ceiling cassettes versus wall heads are the main variables.

See the full mini split installation cost guide — by material, size and region →

Straight answer

When mini split installation is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

You have good ductwork and you are conditioning the whole house. If ducts already reach every room in decent condition, a ducted system will usually cost less to install and give you a single point of maintenance. Mini splits earn their place where ducts are absent, inadequate or impractical.
You want more than about four zones. Per-zone cost adds up quickly, and past three or four heads a ducted heat pump or a central system frequently comes in lower with better whole-house balance. Get both priced before you commit to a five-head design.
You cannot accept the look of the indoor heads. This is a real objection and it is worth taking seriously. The units are visible on the wall, in the room, forever. Ceiling cassettes and low-wall units help, but they cost more and need suitable structure. See one in person before you sign.
The problem is a leaky, uninsulated room rather than an absent duct. Adding a head to a bonus room with an uninsulated knee wall means paying to fight the heat loss every day. Insulate and air seal first — the head you then need will be smaller and cheaper.
You are only trying to solve one month of the year. A permanently installed system with refrigerant lines through your wall is a lot of commitment for four weeks of discomfort. A window or portable unit is not glamorous, but it is the proportionate answer.
Nobody local services them well. Mini splits are a different service skill set from ducted equipment, and in some markets the installers are ahead of the service technicians. Ask who maintains it in year six before you buy in year one.

Your options

Types of mini split installation

Single-zone system

One outdoor unit, one head. The straightforward case.

Ducted heat pump instead

When the ducts are already there and in good shape.

Mini split vs central air

The comparison, side by side.

Compare hvac options side by side →

Straight answer

Can I do this myself?

Two honest warnings on the DIY kits. Handling refrigerant without EPA Section 608 certification is regulated, which is why the DIY route uses sealed pre-charged line sets — go outside that and you are in territory you should not be in. And check the manufacturer's warranty terms before you buy: some void or reduce coverage on self-installed units.

Reasonable to DIY

Choosing head locations and walking the line set route before any contractor quotes — it is your wall
Clearing and levelling the outdoor pad location, and keeping shrubs back from it
Fitting a pre-charged DIY kit if you are genuinely comfortable drilling a through-wall penetration and making a flare-free quick-connect — these kits exist and they work
Ongoing filter cleaning: the mesh filters in the heads pull out and rinse, and doing it monthly in season is the main maintenance the system needs

Call a licensed pro

Any system that is not pre-charged — those need nitrogen pressure testing, deep vacuum evacuation and weighed charge, which needs both licensing and equipment
Any multi-zone system, where branch boxes and per-zone line sizing are involved
The 240V circuit and disconnect, and anything touching the panel
Cold-climate installations where the low-ambient performance and defrost behaviour need configuring rather than accepting defaults

Before you sign

What to check when hiring for mini split installation

How did you size each zone, and can I see the room-by-room numbers?

Per-room sizing is the whole point of a zoned system. A single figure for the house means it was not done.
Why single zone or multi zone for my layout?

There is a genuine engineering answer either way. A contractor who can explain the low-load behaviour of a multi-zone has thought about it; one who defaults to "one box outside is neater" has not.
Where exactly will each head go, and where will the line set run outside?

Agree this on the wall with tape before anyone drills. It is permanent and it is visible from your street.
How long is each line run, and are you adding the extra refrigerant charge for it?

A specific, documented number from the installation manual. A contractor who knows it off the top of their head is a good sign.
Does my electrical panel have capacity, and have you looked at it?

Should be settled at the site visit. Discovering it mid-install is how a one-day job becomes a two-week one.
What is this unit's rated output at my winter design temperature?

If you are heating with it, the 47°F rating tells you nothing about a January night. Ask for capacity at the temperature that actually matters where you live.
Who services this brand locally, and what is the parts lead time?

Some mini split brands are widely stocked and some are not. A three-week wait for a control board in February is a different product than the one you thought you bought.

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Local pros

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Related work

Often done at the same time

Heat Pump Installation

The ducted equivalent

AC Installation

Central cooling instead

Ductwork Installation

If you would rather extend the ducts

HVAC Maintenance

Keeping the heads clean

All hvac services →

Go deeper

Guides & terms

Guides

Heat Pump Buying Guide

All hvac guides →

Terms on this page

SEER2

Full hvac glossary →

FAQ

Mini Split Installation — questions people ask

Still have a question? Talk to our team →

How much does a mini split cost per zone?

A single-zone system installed is usually a few thousand dollars, and each additional head on a multi-zone typically adds a few thousand more — though not linearly, since the outdoor unit is shared. The variables that move it most are the length and difficulty of the line run, whether a condensate pump is needed, whether the electrical panel can take the load, and whether you want wall heads or the more expensive ceiling cassettes.

Can I install a mini split myself?

Partly, and honestly. Pre-charged DIY kits with sealed quick-connect line sets genuinely exist and are designed for competent homeowners — no refrigerant handling, no vacuum pump. What you still need is the confidence to cut a three-inch hole through your wall, mount the units correctly, and get the 240V circuit installed by an electrician. Anything that is not pre-charged requires EPA certification and equipment. Also read the warranty terms first: some manufacturers reduce coverage on self-installed systems.

Do mini splits work for heating in winter?

Yes — a mini split is a heat pump, and cold-climate models are rated to produce useful heat well below freezing. What matters is capacity at your local design temperature, not the headline rating taken at 47°F. Output falls as it gets colder, so cold-climate installations should be sized against the cold night and often keep an existing heat source as backup for the extremes.

How many mini split zones do I need?

One per space you want independently controlled, with a caveat: heads only condition the room they are in, and they do not push air around corners or up staircases. An open-plan main floor may need one; four bedrooms behind closed doors need four, or a ducted solution. This is where the per-zone cost adds up, and where it is worth pricing a ducted system as an alternative rather than assuming ductless is cheaper.

Are mini splits noisy?

The indoor heads are among the quietest options available — inverter compressors ramp rather than switching on and off, so there is no start-up thump and the fan runs low most of the time. The outdoor unit is where the noise is, and it runs at night in summer. Siting it away from bedroom windows and away from a neighbour's boundary is a decision made once and lived with for a long time.

How long do mini splits last?

Comparable to other heat pump equipment when properly installed and maintained, and the maintenance requirement is low but not zero: the mesh filters in each head need rinsing regularly, and the indoor coils need a proper clean periodically. Neglected heads develop mould in the blower wheel and a smell that no amount of air freshener fixes. Ask what the servicing routine is before you buy, not after.