VRF vs Chilled Water: Which System for Your Building?

What You Need to Know

For commercial buildings above 2,000 sqm, the system selection decision almost always comes down to VRF (Variable Refrigerant Flow) or chilled water. Both can heat and cool a building effectively, but they work in fundamentally different ways, and the right choice depends on building size, number of floors, available plant space, and long-term operating strategy.

VRF pipes refrigerant directly from outdoor units to indoor units on each floor. There is no water, no air handling unit, and no cooling tower. It is simpler to install and typically 10 to 20% cheaper on capital cost for buildings under 10,000 sqm. Maximum piping length is approximately 165 metres from outdoor unit to furthest indoor unit, which makes it suitable for buildings up to about 15 storeys.

Chilled water uses a central plant (chiller and cooling tower) to generate chilled water at 6 to 7 degrees, which is then piped to air handling units or fan coil units on each floor. Capital cost is higher, but centrifugal chillers operate at 0.5 to 0.6 kW/kW of cooling compared to 1.0 to 1.2 kW/kW for VRF. For large buildings, the running cost savings compound over time.

The typical crossover point is 10,000 to 15,000 sqm of total floor area. Below that, VRF usually wins on total cost of ownership. Above that, chilled water is more cost-effective over a 15 to 20 year building life.

• Refrigerant charge limits apply to VRF systems in occupied spaces. AS/NZS 5149 sets maximum allowable refrigerant charges based on room volume, refrigerant type, and occupancy classification. R410A systems in offices typically allow up to 0.44 kg/sqm of floor area. Exceeding this requires gas detection and mechanical ventilation interlocks. (AS/NZS 5149:2016)
• Section J energy efficiency requirements apply to both systems. Fan power limits, ductwork insulation, pipe insulation, and economy cycle requirements are system-agnostic. Both VRF and chilled water must comply. Chilled water pipework must be insulated to prevent condensation and energy loss. (NCC 2025 Section J)
• Cooling towers must comply with public health requirements. Cooling towers used in chilled water systems must be registered with the local council and maintained under a risk management plan to prevent Legionella. This adds ongoing compliance cost. (Public Health Act 2010 NSW, AS/NZS 3666)
• Minimum outdoor air ventilation rates are the same regardless of system type. Both VRF and chilled water buildings must provide 10 L/s per person of outdoor air in offices. VRF systems typically use a dedicated outdoor air system (DOAS) or energy recovery ventilator (ERV) to handle ventilation separately from the VRF. (AS 1668.2:2024)
• Economy cycles are mandatory for systems above 40 kW serving a single zone. Chilled water systems with central AHUs easily incorporate economy cycles. VRF systems typically do not have economy cycle capability, so a separate outdoor air system must provide the economy cycle function. (NCC 2025 Section J)
• Time switches and zone controls are required for both systems. All systems above 2 kW cooling must have programmable time switches. Both VRF and chilled water must provide zone control with thermostats in each controlled area. (NCC 2025 Section J)

Consider a new 8-storey commercial office building in Sydney with 12,000 sqm of net lettable area. At 120 W/sqm average cooling load, the building needs approximately 1,440 kW of total cooling capacity. Here is how the two systems compare.

With VRF, you would install outdoor units on the roof or on each floor's balcony/louvre area. A building this size might need 15 to 20 outdoor units, each serving 2 to 4 floors via refrigerant piping through a central riser. Indoor units (cassettes, ducted, or wall-mounted) go on each floor. The piping runs from the roof to the lowest floor would be approximately 30 to 40 metres, well within the 165 metre limit. Capital cost would be approximately $1.8 to $2.4 million for the complete VRF system including outdoor units, indoor units, refrigerant piping, controls, and a dedicated outdoor air system for ventilation.

With chilled water, you would install one or two centrifugal or screw chillers in a basement or rooftop plant room, along with cooling towers, primary and secondary chilled water pumps, and a chilled water riser to each floor. Air handling units or fan coil units on each floor distribute the conditioned air. Capital cost would be approximately $2.2 to $3.0 million, including the plant room fitout, cooling towers, pipework, pumps, AHUs, and controls.

The chilled water system costs 20 to 25% more upfront. But the centrifugal chillers operate at 0.5 to 0.6 kW/kW, compared to the VRF system at 1.0 to 1.2 kW/kW. On a building running 10 hours per day, 5 days per week, the annual energy difference is approximately $30,000 to $50,000. Over 15 years, the chilled water system's lower running costs offset the higher capital cost. The break-even point is typically 8 to 12 years.

Maintenance tells a different story. VRF systems have no cooling tower (no water treatment, no Legionella risk management), no pumps (no mechanical seals to replace), and no large plant room to maintain. Annual VRF maintenance runs $15,000 to $25,000 for a building this size. Chilled water maintenance, including water treatment, cooling tower servicing, pump maintenance, and chiller servicing, runs $30,000 to $50,000 per year. This narrows the running cost gap considerably.

The practical decision often comes down to space. Chilled water needs a dedicated plant room of 60 to 100 sqm, plus cooling tower space on the roof. In a tight urban site where every square metre of floor area is rentable, giving up 100 sqm of basement for a plant room costs $50,000 to $100,000 per year in lost rent. VRF outdoor units sit on the roof or in louvred enclosures on each floor, taking up far less usable space.