[From energycodes.gov] On July 21, 2021, DOE issued a determination that Standard 90.1-2019 will achieve greater energy efficiency in buildings subject to the code. DOE estimates national savings in commercial buildings of approximately:
4.7 percent site energy
4.3 percent source energy
4.3 percent energy cost
4.2 percent carbon emissions
On July 21, 2021, DOE issued a determination that the 2021 International Energy Conservation Code (IECC) will improve energy efficiency in residential buildings. In support of this determination, DOE conducted a technical analysis evaluating the impacts of the updated code (relative to the 2018 IECC edition). DOE estimates national savings of approximately:
9.38 percent site energy savings
8.79 percent source energy savings
8.66 percent energy cost savings
8.66 percent carbon emissions