The third biennial ACEEE City Energy Efficiency Scorecard measures the progress of city policies and programs that save energy while benefiting the environment and promoting economic growth. We ranked 51 large US cities for their energy efficiency efforts across 5 policy areas: local government operations, community-wide initiatives, buildings, energy and water utilities, and transportation. In this year's results, Boston retained its position at the top of the rankings. Joining Boston in the top five were New York, Seattle, Los Angeles, and Portland. The most-improved cities since the last edition were Los Angeles, San Diego, Kansas City, and Phoenix. Overall, we found that the majority of the cities improved their scores, showing that many communities across the country are continuing to take steps to save energy. The Scorecard provides a roadmap for any local government that aims to increase its energy efficiency by learning from other cities' successes and customizing national best practices to suit its own priorities.