What Is a Mini Split? How Ductless Heat Pumps Work

A mini split — short for "ductless mini-split heat pump" — is one of the most popular ways to add efficient heating and cooling to a home, especially one without ductwork. If you've seen a slim white unit mounted high on a living-room wall with a small box outside, that's a mini split. Here's what it is, how it works, and when it's the right tool.

What a mini split is

A mini split is a type of heat pump that delivers heating and cooling without ducts. Instead of pushing conditioned air through a network of ducts, it conditions the air right in the room. A system has two main parts:

• An outdoor unit — the compressor and condenser, about the size of a small AC unit, mounted outside.
• One or more indoor units (heads) — wall-, ceiling-cassette-, or floor-mounted, each blowing conditioned air directly into a room.

They're joined by a line set — thin refrigerant tubing, a power cable, and a condensate drain — that runs through a small (≈3") hole in the wall. A single-zone system has one indoor head; a multi-zone system runs several heads off one outdoor unit, each with its own thermostat.

How a mini split works

Like every heat pump, a mini split moves heat rather than creating it. Refrigerant circulates between the indoor and outdoor units:

• In winter, it absorbs heat from the outdoor air (yes, even cold air holds usable heat), and the compressor concentrates it and releases it indoors.
• In summer, the cycle reverses — it pulls heat from inside your home and dumps it outside, acting as an air conditioner.

Because it moves existing heat instead of burning fuel or running a resistance element, it delivers 2.5 to 4 units of heat for every unit of electricity (its COP), which is why mini splits are so cheap to run compared with electric baseboards or a resistance furnace. Modern inverter-driven compressors ramp smoothly up and down instead of cycling on and off, which keeps temperatures steady and efficiency high.

Pros and cons

What a mini split costs

Pricing scales mostly with the number of zones and the capacity you need:

• Single-zone: roughly $3,000–$5,000 installed.
• Multi-zone: $5,000–$15,000+, rising with each indoor head.

For a tailored figure, the heat pump cost calculator breaks down equipment, labor, and a cost-by-type comparison (a mini split is the "ductless" option). To get the capacity right first, the heat pump sizing calculator estimates the tons/BTU your space needs — oversizing and undersizing both hurt comfort and efficiency.

Is a mini split right for you?

A mini split is an excellent fit when you:

• Have a home or room without ducts (additions, garages, sunrooms, older houses).
• Want zoned control — different temperatures in different rooms.
• Want to replace expensive electric baseboard heat with something far cheaper to run.
• Want one system that heats and cools.

If your home already has good ductwork and you want to condition the whole house from one system, a ducted (central) heat pump may be simpler — see our ductless vs central heat pump comparison. And to understand the running-cost advantage in dollars, read heat pump vs electric resistance heat. Whatever you choose, size it with a Manual J load calculation from a qualified installer before you buy.