ASHRAE标准118.2提供了对直接加热的家用热水器和家用商用热水器的效率和热水输送能力进行评级的测试程序。本标准2022年版是一次实质性修订，源自《测量热水器能耗的统一试验方法》（联邦法规，第10篇，第430部分B子部分附录E）。2022年版将测试条件和绘制模式移至信息性附录A“U。 S.测试变量的值”，以便测试方法可以应用于其他条件，并绘制适用的模式。其他变化包括明确备用期的时间、明确恢复期的结束、规定在出口处测量计算中使用的水的密度、调整较小水箱的FHR流量，以及定义一个抽水时间限制（如果热水器能够跟上FHR流量）。

ASHRAE Standard 118.2 provides test procedures for rating the efficiency and hot-water delivery capabilities of directly heated residential water heaters and residential-duty commercial water heaters.The 2022 edition of the standard is a substantial revision, derived from the Uniform Test Method for Measuring the Energy Consumption of Water Heaters (Code of Federal Regulations, Title 10, Appendix E to Subpart B of Part 430).The 2022 edition moves conditions of the test and draw patterns to Informative Appendix A, “U.S. Values for Test Variables” so that the test method can be applied with other conditions and draw patterns as applicable.Other changes include clarifying the timing of the standby period, clarifying the end of the recovery period, specifying that the density of water used in calculations be measured at the outlet, and adjusting the FHR flow rate for smaller tanks and defining a draw time limit if the water heater can keep up with the FHR flow rate.