Water Efficiency Performance and Metering
What the domain tests
WE performance items test whole-building water accounting, irrigation and cooling-tower metering, and how actual consumption is converted into credit documentation. The focus is measured water use, not fixture-count calculations from design.
Core rules
- Use 12 months of actual water bills or meter readings for the performance period, with meter boundaries that match the building and associated site.
- Whole-building water metering is the baseline. Submetering is used for major end uses such as irrigation, cooling towers, and tenant spaces where the credit requires visibility.
- Outdoor water use should be tracked separately from indoor use so irrigation efficiency and landscape decisions can be evaluated.
- Alternative water sources-harvested rainwater, reclaimed water, condensate-can reduce potable demand, but the credit must reflect actual metered use and safe accounting.
- Compare performance against the rating system’s baseline or previous period as the credit requires; do not mix potable and nonpotable volumes without documenting the basis.
- Leaks and meter errors can dominate results; investigate anomalies before submitting.
Worked example
A building uses 8 million gallons of potable water in 12 months. A submeter shows 1.2 million gallons for irrigation, and a cooling-tower meter shows 1.5 million gallons. The team reports total potable use and the end-use breakdown, checking that the irrigation meter is not double-counted in the domestic meter. If reclaimed water supplies 300,000 gallons of irrigation, that volume is documented separately and not added to potable consumption.
Traps
Using fixture calculations instead of bills; reporting only indoor water; double-counting a submetered end use inside the main meter; ignoring cooling-tower blowdown; and treating a one-month leak as normal performance.