Hot water savings from water-efficient lavatory fittings lead to reductions in water heating energy consumption, and ultimately to decreases in carbon emissions. This paper characterizes existing and proposed approaches used to estimate hot water savings and carbon emissions reductions stemming from the U.S. Environmental Protection Agency's WaterSense program. Also described are refinements that improve the accuracy of residential hot water use percentage estimates of lavatory fittings. The authors conclude that (1) hot water percentages for showers and faucets calculated using up-to-date, publicly available national data are consistent with those found by regional studies and household-level models of water use; (2) the accuracy of heating energy savings estimates attributable to WaterSense-labeled lavatory products, as well as associated emissions reductions, can be refined by modifying the existing energy factor/uniform energy factor (EF/UEF)-based estimation approach with available data. The refined approach accounts for more nuanced conditions than the EF/UED-based approach but depends on data not always available; and (3) the approaches described and intermediate outputs can be generalized for other water conservation programs or estimating purposes.

节水型马桶配件可节省热水，从而减少水加热能耗，并最终减少碳排放。本文描述了用于估算美国环境保护署 WaterSense 计划产生的热水节约量和碳排放减少量的现有方法和提议的方法。还描述了改进厕所配件的住宅热水使用百分比估计的准确性。作者得出结论：(1) 使用最新的、公开的国家数据计算的淋浴和水龙头的热水百分比与区域研究和家庭级用水模型发现的一致；(2) 可归因于带有 WaterSense 标签的马桶产品的加热节能估算的准确性，以及相关的减排量，可以通过使用可用数据修改现有的基于能源因子/统一能源因子 (EF/UEF) 的估算方法来完善。与基于 EF/UED 的方法相比，改进的方法考虑了更细微的条件，但取决于并非总是可用的数据；(3) 所描述的方法和中间输出可以推广用于其他节水计划或估算目的。