In response to California's policy target for all new commercial construction to be zero-net energy (ZNE) by 2030, Pacific Gas and Electric Company (PG&E) commissioned a comprehensive study to gauge the technical feasibility for ZNE by looking at energy use intensity (EUI) of the California building stock. Nine building types in five California climate zones, 14 energy conservation measures (ECMs), up to two HVAC systems per building type, and renewable energy strategies were considered in this study. A parametric study of this level of complexity would require over 2 million building energy simulations to explore all possible combinations. Instead, a parametric analysis tool with an innovative methodology was developed, which drastically reduces the number of energy simulations needed to about 200 for a similar level of combinations, complexity, and accuracy. This tool provided PG&E with an interactive user interface, showing instantaneous feedback on energy conservation measures necessary to reach the ZNE goal in California. This paper presents the motivation, functionality, and methodology behind the parametric analysis tool.