The transition to renewables cuts across the entire urban energy landscape, from buildings to transport, to industry and power. Renewables can bring tremendous benefits to cities, including cleaner air, modern services and improved living spaces. At the same time, cities are crucial to the world’s transition to a low-carbon economy, accounting for 65% of global energy use and 70% of man-made carbon emissions. Renewable Energy in Cities explores potential for urban communities to scale-up renewables by 2030, based on estimated energy use 3,649 cities around the world. It finds that every city has massive potential to cost-effectively boost renewable energy use at the local level. The report outlines three priority areas where cities can take action: renewable energy in buildings (for heating, cooling, cooking, and appliances); sustainable options for transport (electric mobility and biofuels); and creating integrated urban energy systems. By highlighting the best practices from cities around the world, this report examines the policies and technologies by which cities can bring about a renewable energy future. It provides concrete examples of how municipal leaders and administrators can accelerate the switch to renewable energy at the local level by acting as planners, regulators, financiers and operators of urban infrastructure.