The equipment for a ductless system can be priced on a website in a minute. The installed price is a different number and it is made of several things.
The components
The outdoor unit and the heads.
The line set — insulated refrigerant lines, one pair per head, run from each indoor unit to the condenser. Length matters, and so does the route.
The wall penetration and line hide, the cover that conceals the lines on the exterior. Bare lines on a front elevation look like an afterthought and cost less.
Electrical — a dedicated circuit and disconnect for the outdoor unit, and in some cases a panel upgrade.
Mounting — a wall bracket or a ground pad, raised where snow requires it.
Condensate — a gravity drain where possible, a small pump where not.
Vacuum and commissioning — evacuating the lines properly and verifying the charge.
Permit and inspection.
Where quotes diverge
Line set length and route. A head on the far side of the house from the condenser is a longer run and often a harder one.
Number of penetrations, and how much of the run is exposed.
Electrical work, which varies from a straightforward circuit to a service upgrade.
Head type. A ceiling cassette costs more to install than a wall-mounted head because it needs ceiling access and support.
Whether the interior is finished, since concealed runs in finished walls are far more work than a short run through an exterior wall.
The step that is not visible and matters most
Evacuation. The refrigerant lines must be evacuated with a vacuum pump to remove air and moisture before the charge is released.
Moisture in a refrigerant circuit forms acid and destroys the compressor over time. This step takes time and equipment, and it is the one most often shortened.
A properly commissioned system has a documented micron reading at the end of evacuation. Asking for it is the single best question to put to a ductless installer.
The DIY question
Pre-charged line set kits are sold for do-it-yourself installation, with quick-connect fittings that avoid the need for evacuation.
They are legitimate products with real trade-offs: the line lengths are fixed, the fittings are a long-term leak point, the efficiency is generally lower than the equivalent professionally installed system, and the manufacturer's warranty terms differ.
Refrigerant handling by an uncertified person is also regulated. For a garage or a workshop the trade-off may be reasonable; for a whole-house heating system it is a large bet on a fitting.
What to insist on
A room-by-room load calculation, not a head size picked from area alone.
The evacuation reading.
The connection ratio on a multi-zone system, and the condenser's minimum output.
A permit, where required.
The line set length used, compared to the manufacturer's maximum.
Rebates
Ductless heat pumps are heavily supported by federal credits and by state and utility programmes, and cold-climate rated models often qualify for the largest amounts.
Programmes usually require a qualifying model from a published list, installation by a participating contractor, and submission within a window. The requirements are worth reading before choosing equipment rather than after.
Where the money is best spent
Correct sizing first, a proper evacuation second, and the head placement third.
Efficiency tier matters less than any of them, because a well-specified ductless system is already efficient and a badly commissioned one is not, whatever its rating says.
Line hide and the exterior
The refrigerant lines, the condensate line and the control cable run together from each head to the outdoor unit, and on the outside of the house they are either concealed in a moulded channel or left as an insulated bundle taped to the wall.
The channel costs more and it is the difference between an installation that looks designed and one that looks retrofitted. On a rear elevation it may not matter; on the front of the house it does.
Ask what the exterior will look like and where the penetrations will be, because that is decided on the day and it is permanent.
Servicing later
Filters in the heads are washable and are the owner's job, monthly in heavy use.
Beyond that, ductless equipment needs the indoor coil and blower wheel cleaned periodically — they collect dust and, in humid conditions, biological growth that produces an odour. This is a specific service that not every contractor offers, and it is worth confirming availability locally before choosing a brand with limited local support.