Ductless
up to 20+SEER2
Typical top rating
No duct losses; head-by-head control
Ductless vs central air
If the house already has good ducts, ducted wins on cost per ton and on how the air feels. If it has none, or bad ones in an attic, ductless usually wins. The interesting cases are in between.
Updated 2026-09-04
Our pick — ducted where good duct exists; ductless where it does not, or where one or two rooms are the problem
Central ducted
13.4–18SEER2
Common range
Lower cost per ton; even, quiet delivery
The duct is the whole argument
A ducted system's rating is measured at the equipment. What reaches the rooms depends on the duct: leakage, and conduction through duct running outside the conditioned envelope. Attic ductwork in a hot climate can lose a serious fraction of the capacity it was given before it reaches a register.
A ductless head has no duct at all. Its rated capacity lands in the room. That is why a 20 SEER2 ductless system in a house with bad attic duct can outperform a nominally similar ducted one by more than the ratings suggest — and why it stops being true the moment the duct is good and inside the envelope.
The comparison
| Factor | Ductless | Central ducted |
|---|---|---|
| Cost per ton installed | Higher, and rises with head count | Lower, especially if duct exists |
| Duct losses | None | Real, and worst in an attic |
| Zoning | Per head, by default | Needs dampers and a controller |
| Air delivery | One throw per room; doors matter | Even, through multiple registers |
| Filtration | Small washable screens per head | One central filter, any depth or MERV |
| Fresh air and humidity control | Hard to add centrally | Straightforward — one air stream |
| Visual impact | A head on the wall in every room | Registers only |
| Install disruption | Line-set penetrations, minimal demolition | Chases and soffits if duct must be added |
| Maintenance | Clean every head; more outdoor connections | One filter, one coil |
Where the crossover sits
Roughly at four heads. One or two heads — an addition, a bonus room, a converted garage — and ductless is clearly cheaper and simpler. Five or six heads in a whole house and the equipment cost, the number of outdoor connections and the maintenance burden usually make a ducted system the better buy, if there is any way to route duct.
Multi-zone systems oversize easily
Head sizes come in a coarse ladder. Round every room up and a 30,000 BTU/h house ends up with 42,000 BTU/h of heads, each of which has a minimum output it cannot go below. The mini split sizing calculator prints that ratio so you can see it before it is installed.
The hybrid answer is often best: keep the ducted system for the main body of the house and put one ductless head in the room the duct has never served — instead of retrofitting dampers into a trunk that was never designed for them.
Buying checklist
- A room-by-room load, not a head per room by habit.
- Combined head capacity against the whole-house load — the oversize ratio.
- For ducted: a measured static pressure reading before the duct is called adequate.
- Where the ducts run. Attic duct in a hot climate changes the answer.
- Federal minimums either way — 13.4 SEER2 for split air conditioners, 14.3 for split heat pumps.
Sources: 10 CFR 430.32(c)(5)(ii) (read 2026-09-04)
Related
Mini Split Sizing Calculator
BTU/h per zone and how many heads a house actually needs.
BTU/h · zones
HVAC Zoning Systems
Dampers, bypass, and why a zoned system needs a variable-speed blower.
10 min
Duct Size Calculator
Round and rectangular duct sizes from CFM and friction rate, with equivalent diameter.
CFM · in. w.c./100 ft
SEER2 Savings Calculator
Annual cooling cost and payback when you move from one SEER2 rating to another.
SEER2 · $/yr