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.