10 CFR §431.110

1. (a)Each commercial storage water heater, instantaneous water heater, and hot water supply boiler (excluding residential-duty commercial water heaters) must meet the applicable energy conservation standard level(s) as specified in the table to this paragraph. Any packaged boiler that provides service water that meets the definition of “commercial packaged boiler” in subpart E of this part, but does not meet the definition of “hot water supply boiler” in subpart G of this part, must meet the requirements that apply to it under subpart E of this part.
2. (b)Each unfired hot water storage tank manufactured on and after October 29, 2003, must have a minimum thermal insulation of R-12.5.
3. (c)Each residential-duty commercial water heater must meet the applicable energy conservation standard level(s) as follows: