This report summarizes the experience and results from a battery electric bus (BEB) demonstration funded by the Federal Transit Administration (FTA) under the Transit Investments for Greenhouse Gas and Energy Reduction (TIGGER) program. In 2010, King County Metro transit agency in Seattle, Washington received funding from a TIGGER award to add three electric buses to its fleet. The buses in service at King County Metro are 40-foot electric transit buses built by Proterra. FTA is collaborating with the U.S. Department of Energy (DOE) and National Renewable Energy Laboratory (NREL) to conduct in-service evaluations of advanced technology buses developed under its programs. This report presents evaluation results for the buses in comparison to a selection of conventional fuel buses. The focus of the analysis is on one year of data from April 2016 through March 2017.