Mini Split or Central AC: Which One Fits Your House

How each one works

A central system has one outdoor condenser and one indoor air handler or furnace coil, and moves cooled air through ducts to every room. One thermostat, one filter, one set of equipment to maintain.

A ductless mini split has one outdoor unit and one or more indoor heads, each mounted on a wall or ceiling in the room it serves, connected by a refrigerant line set through a small hole in the wall. Each head has its own control. Most mini splits are heat pumps, so they heat as well as cool.

Where a mini split wins

• A house with no ducts: DC row houses, Old Town Alexandria, pre-war houses in Hyattsville, Takoma Park and Del Ray
• A room the ducts never reached: an addition, a finished attic, a garage conversion, a sunroom
• A basement apartment or in-law suite that needs its own control
• One room that is always hot upstairs and does not justify reworking the whole duct system
• A condo where the shared system is the building's problem and your unit needs its own

The one hot room case is the most common reason we install a single head.

Where central wins

• The house already has ducts in reasonable shape
• You want one thermostat and one filter rather than a head and a remote in every room
• The house has five or more rooms to cool, where a head in each one adds up fast
• You do not want wall units visible in the living spaces
• The system is also the heating, and the house has gas and a furnace worth keeping

What each one costs more for

A mini split's price scales with the number of heads. One head for one room is a modest job. Six heads for a whole house is a large one, and a central system with new ducts is often cheaper, if the ducts can be run.

A central system's price scales with the ducts. If they exist and are sound, the changeout is direct. If they have to be added to a house that never had them, that is the expensive part, and the mini split starts to win.

We do not publish prices for either, because the house sets them. The estimate is free, it is in writing and it shows both when both are possible.

Things people find out afterwards

• A mini split head does not pull air from the rest of the house, so a closed door makes a closed room
• Mini split filters are in the head and need washing, not swapping, and nobody does it
• A single-head mini split in a bedroom is quieter than most people expect; the outdoor unit still needs a place to sit
• Central systems dehumidify the whole house in one pass, which matters in a DMV July
• Both need a condensate path, and a mini split head on an interior wall can need a small pump to get rid of it

How we decide on the first visit

We look at the ducts, if any, the attic, the panel and where a condenser or outdoor unit can sit. In a historic district we check what can be seen from the street. Then we size the load for the house, and only then do we talk about equipment. The AC installation page covers what the install itself involves.