Standard 189.1 energy performance compliance requirements include energy cost performance and CO2 emissions compared to a baseline building using energy modeling rules and other underlying assumptions. This approach was intended to account for the economic interests of the owner as well as the environmental impact of the proposed building while being sensitive to local conditions and building characteristics. This presentation will review the underlying assumptions, key variables and metrics, and rationale for selection of performance requirements that differ from those in the 2015 version of IgCC.