Thermal power plants waste significant amounts of energy in the form of heat, leading to major issues related to efficiency loss and environmental degradation. This energy loss is known as waste heat. Waste Heat Recovery (WHR) systems provide a practical way to capture this unused heat and convert it back into useful power or process heat. By doing this, power plants become more efficient and significantly reduce harmful emissions. This review focuses on the main WHR technologies used in thermal power plants. Various methods are employed, such as standard heat exchangers, the Organic Rankine Cycle (ORC), the Kalina cycle, and newer systems that use supercritical CO₂. In this article, the system is evaluated by determining its efficiency through thermodynamic analysis. It also considers whether the technology is affordable in terms of economic factors. Additionally, WHR helps control emissions caused by waste heat from power plants. By recovering waste heat, we can reduce global warming, which is a critical issue to address to ensure a safe environment. Finally, there are promising future directions, such as using thermoelectric generators (devices that turn heat directly into electricity) and advanced methods like AI-based optimization. Overall, this paper shows that recovering waste heat is essential for cutting costs, saving energy, and making thermal power generation more sustainable.