[en] Cities are directly responsible for around two-thirds of global final energy use as well as for significant indirect consumption of energy that is embodied in materials, products and other goods. Due largely to this energy use, cities account for an estimated 75% of global carbon dioxide (CO₂) emissions. In addition, cities account for 55% of the global population and for more than 80% of global gross domestic product. Thus, shifting to renewable energy in cities is critical to decarbonizing the global energy system. At the same time, cities offer a lever to advance the transition towards renewable energy in all end-use sectors, not only in power but also in heating and cooling and in transport. Renewable energy offers cities the opportunity to achieve a wide range of objectives. Through their various roles, including urban planning and the provision of numerous services, cities are well-positioned to increase the use of renewable energy in their own activities and to support the deployment of renewables more broadly, while simultaneously achieving local objectives such as reducing air pollution to improve public health, mitigating climate change, supporting the local economy and building resilient infrastructure. City governments around the world have set renewable energy targets. To achieve these targets, cities are using a variety of options at their disposal, including harnessing their own purchasing power and creating local policies to encourage greater public and private uptake of renewables. Some cities have used their close ties to the community to engage residents, businesses and other local stakeholders. Many have served as trend setters, influencing and advocating for increased support for renewables at the state/provincial and national levels, and joining together in national and global city networks to exchange ideas and help drive renewable energy and climate action around the world. Despite their many points of leverage, cities face challenges in their efforts to pursue ambitious energy and climate strategies. In many cases, municipal efforts are hampered by policies and regulations at higher levels of government. A lack of co-ordination among city departments also can impede progress. A city's ability to advance a renewable energy agenda depends heavily on local characteristics, including their own financial resources, access to external financing, the size of the tax base, economic growth and the local administrative capacity and authority.