This study demonstrates the trade-offs between vehicle energy consumption and on-site solar energy potential in a city landscape. While higher urban density may curb many of the problems associated with sprawl mainly by reducing vehicle travels and associated energy use, it can also limit on-site rooftop solar energy utilization due to more shade on rooftops in dense urban settings and less available rooftop area per person. Using travel survey, Geographic Information System (GIS) and Light Detection and Ranging (LiDAR) data, we estimated vehicle energy use and rooftop solar potential in the City of San Francisco as a case study and calculated possible offsetting effects between vehicle energy consumption and rooftop solar potential. Given the prevalence of gasoline-based vehicles and today's solar photovoltaic (PV) panel efficiency, vehicle energy use per capita appears to exceed energy generated by rooftop solar PVs per capita across all density ranges, especially in lower density environments. At the point when electric cars and advanced, highly efficient solar PV panels penetrate the market, the results change based on the combination of different technological options. A significant reduction of energy consumption can be achieved through the immediate and rapid spread of energy efficient technologies in vehicles and solar PVs along with the long-term effect from gradual urban densification.