Cities have key energy challenges related to transportation, industry, and buildings. Urban areas already consume two thirds of the world’s energy, with a mix heavily dependent on fossil fuels. Cities are tasked with maintaining economic growth and the safety and security of their citizens as urbanization rises, and are among the regions most affected by climate change and sea-level rise. To understand how cities are managing energy, we analyzed three cases studies of projects applying new technologies: the Brooklyn LO3 microgrid, Berlin EURUF campus, and the Ashiya PanaHome grid. We find they use similar technologies, but the urban energy business case is not straightforward, driving outsized interest in microgrids, stationary energy storage, and distributed generation.