This chapter develops a mathematical programming model for optimal energy sector planning with CCS and renewables deployment. The model considers a variety of carbon capture (CC) options for the retrofit of individual thermal power generation units. For comprehensive planning, the Integrated Environmental Control Model is employed to assess the performance and costs of different types of power generation units before and after CC retrofits. A case study of Taiwan’s energy sector is presented to demonstrate the use of the model for complex decision-making and cost trade-offs in the deployment of CC technologies and additional low-carbon energy sources. Different scenarios are analyzed to identify the optimal strategy of energy mix to satisfy the electricity demand and various planning constraints.