Should I use a split system or central plant for my commercial building?

It depends on building size. Split systems suit spaces under 200 square metres with one or two zones. VRF systems suit mid-size buildings from 500 to 5,000 square metres. Central plant (chilled water) suits large buildings over 5,000 square metres, multi-storey towers, hospitals, and data centres. The crossover point is where the higher upfront cost of a larger system pays back through lower running costs over the building's life.

What is a VRF air conditioning system?

VRF stands for Variable Refrigerant Flow. One outdoor unit connects to many indoor units through refrigerant piping. Each indoor unit controls its own temperature independently. Some zones can heat while others cool at the same time. VRF is the most common choice for commercial fitouts and mid-rise buildings in Australia because it balances upfront cost, efficiency, and zone control.

When does a building need a chilled water central plant?

Central plant makes sense for buildings over 5,000 square metres, multi-storey towers, hospitals, data centres, and any building with high cooling loads that run most of the day. A chiller produces chilled water that gets pumped to air handling units or fan coil units on each floor. The upfront cost is the highest of all three system types, but the running cost per kilowatt is the lowest at scale, and the equipment lasts 20 to 30 years.

Which commercial air conditioning system is cheapest to run?

Central plant (chilled water) has the lowest running cost per kilowatt for large buildings. VRF is 20 to 30 percent more efficient than split systems at part load. Split systems have the highest running cost per kilowatt but the lowest upfront cost. Over a 20-year lifecycle, VRF and central plant almost always cost less in total than split systems for buildings over 500 square metres.

Split System vs Central Plant: Which Is Right for Your Commercial Building?

Section 1

Three System Types

Commercial buildings use three main HVAC system types: split systems (DX), VRF (variable refrigerant flow), and central plant (chilled water). Each suits a different building size, budget, and operating profile.

The right choice depends on floor area, number of zones, expected lifespan, and how much you want to spend upfront vs over 20 years. Pick the wrong system and you either overspend on day one or overpay on energy bills for the life of the building.

This memo breaks down all three options with real numbers so you can make the right call for your project.

Section 2

Split Systems (DX)

1

Split Systems (DX)

Best for: Small tenancies under 200 m², single-zone spaces, short-lease fitouts.

One outdoor unit connects to one indoor unit. A multi-split version connects one outdoor unit to up to 5 indoor units. Simple to install. Lowest upfront cost at $3,000–$8,000 per system installed.

Refrigerant pipe runs are limited to about 30 m between indoor and outdoor units on standard models. Each system runs independently. If one fails, the others keep working.

Typical lifespan is 10–15 years. Running cost per kilowatt is higher than VRF or central plant because the compressor runs at full speed or not at all on most models.

Trade-off: Lowest upfront cost, but highest energy cost per square metre. Good for small spaces or short leases where you will not own the building long enough for a bigger system to pay back.

Section 3

VRF (Variable Refrigerant Flow)

2

VRF (Variable Refrigerant Flow)

Best for: Mid-size buildings 500–5,000 m², multi-zone requirements, commercial fitouts and mid-rise buildings.

One outdoor unit serves many indoor units. Large systems connect 60 or more indoor units to a single outdoor unit. Each zone controls its own temperature. Some zones can heat while others cool at the same time (heat recovery VRF).

Pipe runs reach 100–165 m between outdoor and farthest indoor unit, depending on the manufacturer. This makes VRF practical for buildings up to 10 storeys without a plant room on every floor.

Upfront cost sits at roughly $150–$250 per m² installed. VRF uses inverter-driven compressors that ramp up and down with demand. Part-load efficiency is 20–30% better than fixed-speed split systems. Typical lifespan is 15–20 years.

VRF is the most popular choice for commercial fitouts and mid-rise buildings in Australia. It balances cost, efficiency, and zone control better than the other two options in this size range.

Trade-off: Higher upfront cost than splits, but much lower running cost. Requires specialist installers and careful pipe sizing. Refrigerant leak detection is harder in long pipe runs.

Section 4

Central Plant (Chilled Water)

3

Central Plant (Chilled Water)

Best for: Large buildings over 5,000 m², multi-storey towers, hospitals, data centres, and buildings with high cooling loads that run most of the day.

A chiller produces chilled water at about 6°C. Pumps move that water through insulated pipes to air handling units (AHUs) or fan coil units (FCUs) on each floor. The AHUs blow air over the chilled water coil and distribute cool air through ductwork.

Upfront cost is the highest of all three types at $200–$400+ per m². You need a dedicated plant room for the chiller, pumps, cooling tower (if water-cooled), and controls. Water-cooled chillers also need roof space for the cooling tower.

Running cost per kilowatt is the lowest at scale. A water-cooled centrifugal chiller can achieve a COP of 6.0 or higher at part load. That is roughly twice the efficiency of a split system. Typical lifespan for the chiller is 20–30 years. The distribution pipework, AHUs, and FCUs last 25+ years with proper maintenance.

Trade-off: Highest capital cost and most complex to design and install. But for large buildings, the lifecycle cost (capital + energy + maintenance over 25 years) is lower than any DX-based system.

Section 5

How to Choose

Under 200 m²: Split systems. Low cost, simple install, fast to replace.
200–500 m²: Multi-split or small VRF. The crossover point where VRF starts to make sense if you need more than 3 zones.
500–5,000 m²: VRF. Best balance of cost, efficiency, and zone control for this size range.
Over 5,000 m²: Central plant. The only system that scales efficiently for large buildings.
Mixed-use with diverse loads: Central plant. Retail on the ground floor, offices above, and a restaurant on the top floor all have different load profiles. Central plant handles this better than any DX system.
Tight budget, short lease: Split systems. Spend less upfront if you will move out in 5 years.
Long-term ownership: VRF or central plant. Lower lifecycle cost over 15–25 years offsets the higher upfront spend.

Section 6

Who Needs to Know What

Section 7

References

AIRAH, HVAC Systems Handbook, Australian Institute of Refrigeration, Air Conditioning and Heating
National Construction Code 2022, Volume One, Section J — Energy Efficiency
AS 1668.2:2012, The use of ventilation and airconditioning in buildings — Part 2: Mechanical ventilation in buildings
ASHRAE, HVAC Systems and Equipment Handbook, Chapter 18: Variable Refrigerant Flow Systems
ASHRAE, Equipment Life Expectancy Chart, ASHRAE Owning and Operating Cost Data

Split System vs Central Plant: Which Is Right for Your Commercial Building?

Three System Types

Split Systems (DX)

Split Systems (DX)

VRF (Variable Refrigerant Flow)

VRF (Variable Refrigerant Flow)

Central Plant (Chilled Water)

Central Plant (Chilled Water)

How to Choose

Who Needs to Know What

Need this engineered for your project?

References

Related design memos

VRF System Design for Multi-Storey Commercial

VRF vs Chilled Water: Which System for Your Building?

VRF vs Ducted Split System for Commercial Buildings