Mayors all over the country are implementing a variety of policies and programs to help their cities achieve clean energy goals, and prioritizing energy efficiency is a vital step. Beyond the direct benefits of reducing costs and carbon pollution, energy efficiency generates health benefits for residents, strengthens the resilience of the grid, complements equity goals, and spurs economic development and job creation. This toolkit describes seven strategies mayors can implement to improve the energy efficiency of their cities. It includes foundational policies, current city best practices, and many useful resources for policy and program development.