As leading cities and states seek to meet their aggressive climate, energy, and decarbonization goals, they are turning increasingly to mandatory policies that require improved energy and emissions performance across their existing building stock. The most comprehensive of these policies is the BPS, in which performance thresholds are set that building owners must meet at a specified time or when a triggering event occurs. A BPS can address a range of emissions, energy and grid-related goals. This paper examines technical approaches used to set the key metrics for both buildings and fuels in performance standard legislation.