Sub-Metering Requirements for Water

What You Need to Know

Water sub-meters track how much water different parts of a building use. Green Star and NABERS both require them. Without sub-meters, you cannot get a NABERS Water rating or earn Green Star water credits. The rules are straightforward: if a use is big enough to matter, it needs its own meter.

• Any common water use that takes 10% or more of total building water must have its own meter (Green Star Buildings v1, Credit 3)
• Floors with multiple uses (e.g., office and retail) must have each use separately sub-metered (Green Star Buildings v1, Credit 3)
• Floors with multiple tenants or owners must have each tenancy separately sub-metered (Green Star Buildings v1, Credit 3)
• All meters must record readings at intervals of 1 hour or less and connect to a monitoring system (Green Star Buildings v1, Credit 3)
• Meters must be commissioned and validated per the current NABERS non-utility meter protocol or NMI standards (Green Star Buildings v1, Credit 3)
• Sub-meters must meet IEC standards and NABERS metering requirements (Green Star Buildings v1, Credit 3)
• NABERS requires 12 months of quality-checked interval data before issuing a Water rating (NABERS Water, Chapter 6)
• In Queensland, sub-meters are mandatory in new buildings with separate lots drawing from a shared water service (QLD Plumbing and Drainage Act)
• Meter accuracy must meet Class 2 per NMI R 49.1 (AS 3565.1-2010)
• From 1 May 2026, all new Green Star projects must register under Buildings v1.1 (GBCA)

Take a 10-storey commercial office with a cooling tower, ground-floor retail, and a landscaped podium. You will need sub-meters on the cooling tower make-up line, the irrigation supply, each retail tenancy, the base building amenities on each floor, and the hot water plant. That is at least 15 meters before you count individual office tenancies.

Each meter needs a pulse output so the BMS can collect interval data. The BMS logs readings every 15 to 60 minutes. NABERS will not accept manual reads - you need 12 months of logged data before you can apply for a rating.

Meter placement matters. Install meters at ground level or in accessible risers. A meter buried behind a ceiling panel on level 8 will not get maintained. Leave at least 300 mm of clear space on each side for removal and calibration.

One real example: a Queensland retail centre installed monitoring on its cinema water supply and found overnight consumption 60 times higher than normal. Daily water costs dropped from $333 to $73 after the leak was fixed. That single meter paid for the entire sub-metering system within weeks.