The traditional power generation and distribution systems will be supplanted by the Internet of Energy, which accelerates the necessity to know the appropriate computation tools to perform any research in this future smart grid arena. However, there is a plethora of computational tools in this area, which challenges the researchers to find an appropriate tool based on their research objectives. Therefore, this article presents a comprehensive study about existing simulation tools related to electrical power generation, transmission, distribution, and associated systems. It provides an overview of more than 150 simulation software in these areas. The tools are classified and discussed based on both traditional and CEN-CENELEC-ETSI smart-grid reference architecture. Typical applications, sources, availability, and strengths of each tool are listed. Each tool has its own strengths and limitations to perform a certain task, and necessary information are provided to help researchers to find an appropriate computational tool for their specific research goal.