Ducted vs Split System: Which Is Right for Your Adelaide Home?
The honest answer for most Adelaide homes: ducted reverse-cycle wins if you’d run 4+ rooms together regularly and your budget tolerates $9,000+; multi-head split wins if you’d run 2-3 rooms or your home doesn’t have the roof void for ducted. The middle case — single-head splits — wins when you only need one room cooled, like a single living room or a primary bedroom. Beyond that, the decision is a function of how you actually use the house, not which system is “better”.
This guide walks the call through six lenses: how you use the house, the budget, the install constraints, the running cost, the resale value, and the maintenance overhead.
The five-second answer
| Your situation | Right call |
|---|---|
| One room you actually use through summer | Single-head split ($2,400-$3,800 fitted) |
| 2-3 rooms you’d run together | Multi-head split ($5,500-$11,000 fitted) |
| 4+ rooms run together with zone scheduling | Ducted reverse-cycle ($9,500-$16,500 fitted) |
| Heritage home with no roof void | Multi-head split (ducted not viable) |
| Budget under $4,000, whole-house cooling | Multi-head split (ducted out of budget) |
| Whole-house climate control on a 700m² block | Ducted reverse-cycle |
If you’re sitting on the fence between multi-head split and ducted, the cost crossover is usually around $9,000-$11,000 — a 5-head multi-split costs about the same as a 4-zone ducted. At that point, the ducted system wins on long-term running cost and quiet operation; the multi-head wins on heritage-friendliness and lower install disruption.
How you use the house
This is the most important factor and it’s the one buyers typically underweight.
Ducted suits:
- Whole-house morning warm-up in winter (kitchen warm by 7am, bathrooms by 7:15am)
- Evening cool-down across the living areas in summer
- Per-room temperature control (master at 22°C, kids at 24°C, living at 23°C)
- Smart-home integration with scheduled zones
- Households that “set and forget”
Multi-head split suits:
- Cooling 2-3 rooms on demand rather than the whole house
- Households that prefer to actively manage which rooms are conditioned
- Heritage homes with no roof void (ducted impossible)
- Budgets in the $7,500-$11,000 range
Single-head split suits:
- One room used heavily (master bedroom, primary living room)
- Studio apartments and 1-2 bedroom apartments
- Bedroom add-on to an existing whole-house system
- Tight budgets under $4,000
Budget — what each option actually costs
| Option | Capacity | Typical Adelaide fitted price |
|---|---|---|
| Single-head split | 2.5kW (bedroom) | $1,800-$2,400 |
| Single-head split | 5kW (medium living) | $2,400-$3,200 |
| Single-head split | 7kW (large living) | $2,800-$3,800 |
| Multi-head split | 2 indoor heads | $4,500-$6,500 |
| Multi-head split | 4 indoor heads | $7,500-$11,000 |
| Multi-head split | 5 indoor heads | $9,500-$13,500 |
| Ducted reverse-cycle | 4 zones, 14kW | $9,500-$13,500 |
| Ducted reverse-cycle | 5 zones, 16kW | $11,500-$15,500 |
| Ducted reverse-cycle | 6 zones, 18kW | $12,500-$16,500 |
The crossover where multi-head and ducted equal each other on price typically lands at the 5-head multi-split / 4-zone ducted comparison, both around $9,500-$11,500. At that price point the choice becomes about which install class fits the house, not which is cheaper.
Install constraints — the deal-breakers
Ducted requires:
- A roof void at least 1.2m in clearance (for the indoor unit and ducting)
- An access pathway from the indoor unit position to each zone
- A return-air location (usually centre of the home, requires a large rectangular ceiling penetration)
- An outdoor compressor location with airflow clearance and reasonable access for service
Multi-head splits require:
- Wall space for indoor heads (typically 90cm wide, mounted high)
- A path for line sets between indoor and outdoor (usually outside walls)
- An outdoor compressor location
For Adelaide heritage homes — particularly Norwood bungalows, Prospect bungalows, and inner-CBD cottages — ducted is often genuinely impossible because the original plaster ceilings have no usable roof void. Multi-head splits are the right call. For modern Adelaide homes (post-2000) with Colorbond rooflines and deep voids, ducted is almost always viable.
Running cost — over a 10-year horizon
The running cost story is more complex than the headline efficiency numbers suggest.
For a typical 4-bedroom Adelaide home running cooling 4 hours/day across November-March (~120 days):
| System | Average kW running | Hourly cost | Seasonal cost (480 hrs) |
|---|---|---|---|
| 4-zone ducted reverse-cycle (14kW) | 3.5kW | $0.85 | $408 |
| 4-head multi-split (running 3 of 4) | 3.0kW | $0.72 | $345 |
| 7kW single-head split (one room) | 1.6kW | $0.38 | $182 |
Ducted runs slightly higher per-hour because you’re cooling more rooms, but the per-room cost is lower because the inverter scales efficiently across zones. Multi-head running 3 of 4 heads is roughly equivalent to ducted at 3 zones — the inverter compressor scales similarly.
The single-head split is cheapest because you’re cooling one room. If you’d ever want to cool 3 rooms simultaneously, you’ve effectively chosen the multi-head/ducted comparison anyway.
For reverse-cycle vs evaporative running cost, the comparison plays out differently again.
Resale value
For a 700m²+ home in Burnside, Mitcham or the Hills, ducted reverse-cycle is genuinely a sale point — buyers expect it on premium homes and quietly downgrade the offer if it’s missing. The Burnside REIWA market data points to a $5,000-$15,000 implicit value gap between equivalent homes with and without ducted reverse-cycle.
For a 3-bedroom Salisbury or Modbury home, the resale lift from ducted versus multi-head is smaller — both demonstrate climate-comfort capability, and most buyers in that price band aren’t pricing the difference.
Maintenance overhead
| System | Service interval | Cost per service | Per-decade total |
|---|---|---|---|
| Single-head split | 12 months | $180-$280 | $1,800-$2,800 |
| Multi-head split (4 head) | 12 months | $280-$420 | $2,800-$4,200 |
| Ducted reverse-cycle (4 zone) | 12 months | $280-$450 | $2,800-$4,500 |
| Coastal-installed (any) | 6 months | as above | 2x the per-decade |
The maintenance overhead is broadly comparable. Ducted has slightly more to clean (return-air filter, multiple zone dampers) but the indoor unit is in a roof void where it’s not exposed to room air contamination. The coastal-rated coil rule — every 6 months for Glenelg, Henley Beach, Brighton — applies to all three classes equally.
The Adelaide-specific calls
A few situations where the answer is more obvious than the generic decision framework suggests:
Coastal suburbs (Glenelg, Henley Beach, Brighton): coastal-rated coil is mandatory regardless of system class. Within those constraints, multi-head splits dominate because most coastal cottages have no roof void. See the Glenelg location page.
Inland heat-load corridor (Salisbury, Modbury, Mawson Lakes): ducted reverse-cycle is friendly here — modern Colorbond rooflines, deep voids, and the +20% sizing rule applies whether you go ducted or multi-head. Ducted with proper sizing wins on whole-home comfort during 41°C heatwaves. See the Salisbury location page.
Adelaide Hills (Stirling, Mount Barker): push for cold-climate spec (Mitsubishi Hyper Heating FH or Daikin Ururu Sarara) regardless of split or ducted. The cold-ambient heating performance matters more than the system class. See the Adelaide Hills location page.
Heritage inner east and inner north (Norwood, Prospect, Walkerville): ducted is usually not viable; multi-head splits with sympathetic outdoor compressor placement is the right call. See the Norwood location page and Prospect location page.
The decision tree, condensed
- Is your home heritage with no roof void? → Multi-head split.
- Is your budget under $4,000? → Single-head split (one room).
- Do you want to cool 4+ rooms together with scheduled zones? → Ducted.
- Do you want to cool 2-3 rooms on demand? → Multi-head split.
- Do you only use one main room through summer? → Single-head split.
Beyond that, the call comes down to install constraints (does the roof void support ducted?) and household preference (set-and-forget vs active management).
What you actually want to ask the installer
When you’re getting a free, written quote, these are the questions that genuinely matter:
- What kW capacity have you specified, and against what room sizes? Undersized systems are the #1 install regret.
- For ducted: how many zones? What’s the zone controller? 4-zone is the minimum for a 4-bedroom home; the controller affects long-term running cost.
- What’s the rated heating capacity at 2°C ambient? Particularly relevant for Adelaide Hills and foothill installs.
- Coastal-rated coil? Mandatory within 4km of the coast.
- Workmanship warranty? 5 years standard, written into every quote.
- Manufacturer warranty registered? Should be — installer registers it on commissioning.
Frequently asked questions
Is ducted always better than multi-head? No — they solve different problems. Ducted wins for whole-house climate control and zone scheduling. Multi-head wins for heritage homes, room-by-room cooling, and lower install disruption. Pick based on how you’ll actually use the system.
Can I add ducted later if I install multi-head now? Sometimes. The outdoor compressor isn’t reusable (different capacity rating), the indoor units aren’t reusable (different format), but the electrical infrastructure and the wall penetrations stay. So you’d be replacing the equipment but reusing the supply infrastructure. The cost saving on a future ducted retrofit is modest — maybe $1,000-$2,000.
Is multi-head reliable? Yes — modern multi-head systems (Daikin Multi-NX, Mitsubishi MXZ, Fujitsu Multi) are mature technology with strong field reliability. The single point of failure (the outdoor compressor) is the same as a single split — if anything, slightly less stressed because it’s running at part-load most of the time.
What about ducted gas vs ducted reverse-cycle? On most modern Adelaide tariffs, reverse-cycle wins on running cost — typically 30-45% cheaper for the same heat output. The gas heating page covers when gas heating is still a sensible call (existing gas connection, mid-life unit you wouldn’t replace until it fails).
How do I know what size system I need? Roughly 0.15kW per m² for a well-insulated room with normal ceiling height. Add 20% for inland heat-load suburbs (Salisbury, Modbury), 10% for west-facing rooms with significant afternoon sun. The sizing guide article walks through the calculation.
Can I get a written quote covering both ducted and multi-head options? Yes — flag it in the form notes. We’ll quote both options on the same enquiry where the install constraints permit.
Ready for a free, written aircon installation quote?
Submit the quote form — we’ll be in touch within 24–48 hours, with your specific job scoped both as ducted and multi-head if useful for the comparison.