Smart grid is the next-generation power grid that will be realized with proactive usage of state-of-the-art technologies in the areas of communications, control, and computing. Greenness is one of the major motivations to develop and analyze smart grid. In a smart power grid, a wireless communications architecture plays a crucial role in improving energy-efficiency, sustainability, and stability. This lecture opens by the introduction of smart power grid models and key concepts (e.g., microgrid, renewable energy resources, Vehicle-to-Grid). Then, we focus on smart grid area networks, including HAN, NAN, FAN, and WAN. Next, the lecture discusses different wireless communications technologies for the smart grid, including wireless sensor networks, machine-to-machine, cognitive radio, and long-range cellular networks. For each wireless communication technology, we will present its advantages, disadvantages, and applications in the smart grid. Finally, we present some recent research advances on communications support for demand response management for efficient power load scheduling.