This document provides an overview of a framework for urban energy system transformation developed by a coalition of five US cities. The framework is intended to help cities take a leadership role in transitioning their energy systems from fossil fuels to 100% renewable energy through establishing shared language, clarifying municipal roles, and defining necessary analysis and strategies. It outlines the evolving role of municipalities in comprehensive energy planning and management. The framework is based on reducing energy demand, decarbonizing supply, and increasing resilience across electricity, heating/cooling, and transportation fuels.