This chapter provides a general description of the basic concepts of electrical generation systems as well as combined heat and power generation systems. First, an overview of the capital as well as operation and maintenance costs for various power generation technologies is presented. Then, a historical background of power generation and cogeneration is outlined. Then, a review of the fundamental theory of power cycles and cogeneration systems is outlined, followed by a description of commercially available cogeneration systems and their components. In addition, some guidelines and examples are presented to carry out feasibility analysis of cogeneration systems. Finally, a cogeneration case study is presented.