A significant new revision of ASHRAE Standard 105 "Standard Methods of Determining, Expressing, and Comparing Building Energy Performance and Greenhouse Gas Emissions" includes compliance requirements related to average and avoided (or marginal) primary energy and greenhouse gas emissions associated with building energy consumption. This paper will provide the rationale for marginal analysis methodologies applied to power generation, and discuss options for determining marginal primary energy and greenhouse gas emission factors attributable to building energy consumption, including pre-combustion and distribution losses. Tabular information will be provided on regional factors for marginal primary energy efficiency and greenhouse gas emissions that include full-fuel-cycle impacts.