This report outlines the evaluation plan and analysis protocol and presents the results from a one-year evaluation of three battery electric buses at King County Metro in Seattle, Washington. The evaluation compared three electric buses to a hybrid fleet, diesel fleet, and trolley fleet. The electric bus fleet accumulated more than 100,000 miles in the first 15 months of revenue service. Findings from the evaluation showed battery buses had an overall average efficiency of 2.36 kWh per mile, or 15.9 miles per diesel gallon equivalent (mpdge). The hybrid buses had an average fuel economy of 6.3 mpdge and the diesel buses had a fuel economy of 5.3 mpdge.