The potential for rapidly urbanizing the global population, however, will pose a mammoth challenge to sustainable development, and especially in the management of energy. This report discusses how integration of big data with the Internet of Things technologies with smart grids can support the realization of Sustainable Development Goal 7: ensuring access to affordable, reliable, sustainable, and modern energy for all, within the context of smart cities. Our approach was mixed-methods, that is, a background literature review supplemented with case studies of smart cities across five continents. We analyzed data on the real-time energy consumption of more than one million IoT devices. The outcomes showed that big data analytics can enhance smart grids, helping to minimize waste energy by up to 23%, while the renewability grows by another 17%. The algorithms for predictive maintenance even helped reduce the downtime of the grid by up to 35%. The research further revealed it has facilitated 12% more access to energy for disadvantaged communities due to an efficient distribution system and dynamic pricing model. In a nutshell, it finds that the proactive implementation of big data and IoT with smart grids is quite important to realize SDG 7, promising a scalable, sustainable urban energy management solution. This, however, leaves and presents increasingly more formidable challenges of addressing concerns over data privacy and equal access to such technologies—a subject requiring further research and policy interventions.