Methodology for the national water savings models– indoor residential and commercial/institutional products, and outdoor residential products

Since 2006, the U.S. Environmental Protection Agency (EPA) has operated WaterSense® in partnership with manufacturers, utilities, and consumer groups. Similar to EPA's ENERGY STAR® role for energy-efficient products, WaterSense® employs a labeling system to identify water-efficient products, homes, and services. As of 2015, the WaterSense® program can claim credit for a total savings of 1.5 trillion gallons of water and $32.6 billion in consumer water and energy bills. Savings are tracked in the National Water Savings (NWS) model that combines innovative analyses with methodologies established in the energy sector. Merging life-cycle cost and national impact analysis models, the NWS model estimates savings from a bottom-up accounting method for individual products. The model extends those savings to the national level by employing parameters such as frequency of product use by a number of people and building type, product lifetime, stock accounting, and market saturation. The NWS model tracks the water and consumer monetary savings of WaterSense-labeled products for residential and commercial water use both indoors and out.