This study proposes a new monthly whole-building water use regression model for weather-normalized water performance evaluation: a combination three-parameter multi-variable regression (3-P MVR) cooling model using outdoor temperature in a change-point model and precipitation amount/occurrence as an additional independent variable. To select appropriate weather variables influencing a building's water use, previous studies on the water use models at the municipal level were reviewed. The selected weather variables were then tested using the multi-year monthly water use data collected from the two separate water meters (i.e., the main building meter for indoor water use; and sprinkler meter for landscape water use) of the case-study office building in central TX. The proposed water use model is based on twelve monthly, building-level water use data, which should be available for most buildings that are supplied water from a municipal provider. This model allows a year-to-year, weather-normalized comparison for self-referencing as well as savings calculations from various water conservation measures. This new method will reduce uncertainty about reported water savings from water conservation measures applied and improve the credibility of water conservation programs. (C) 2013 Elsevier B.V. All rights reserved.