Performance Evaluation of DC EVSE

California's 2045 electrification goals require the deployment of electric vehicle supply equipment that minimizes energy losses while supporting a growing population of electric vehicles. Although DC charging is generally expected to be more efficient than AC charging, limited independently measured data exist to quantify differences in charging pathway efficiency across commercially available systems. This project evaluated the performance of commercially available AC and DC EVSE under controlled laboratory conditions to quantify charging efficiency, characterize energy losses, and assess potential energy savings associated with broader deployment of efficient charging technologies. Four AC Level 2 chargers and four DC Level 1 chargers were evaluated using a standardized testbed. Testing included discrete battery state-of-charge conditions and controlled power throughput scenarios. A second phase of testing evaluated continuous charging sessions from approximately 10% to 80% SOC using a subset of the evaluated chargers to characterize efficiency over a representative charging event. Across the evaluated operating conditions, AC EVSE achieved charging efficiencies between approximately 91% and 93%, while DC EVSE achieved efficiencies between 95% and 97%. ENERGY STAR certification did not consistently correspond to higher measured efficiency, with certified and non-certified AC products exhibiting similar performance. Phase 2 testing showed charging efficiency remained relatively stable throughout extended charging sessions and was in close agreement relative to discrete operating point testing. Economic analysis estimated annual electricity cost savings from DC charging ranged from approximately $10 to $27 per vehicle based on applied TOU structure. Extrapolating the measured efficiency differences to California's existing light-duty zero-emission vehicle fleet indicates potential statewide electricity savings of approximately 173 GWh annually and avoidance of roughly 50.3 million kilograms of carbon dioxide equivalent emissions. These findings demonstrate that DC EVSE provides a measurable charging efficiency advantage over AC EVSE under the various evaluated operating conditions.