Energy security is a very broad concept and has been defined differently in different countries at different times. There are almost one hundred interpretations of energy security and its subsidiary concepts in the existing documents summarized in the study. In the 1970s and 1980s, energy security meant a way of stabilizing the supply of imported oil at a reasonable price against the background of the ban on oil exports and the manipulation of prices by oligopolies. Thus, at that time, energy security was tantamount to having a stable international source of fossil energy. Energy security tended to vary from country to country, was evaluated within a single country, and initially represented energy security only for oil. Later, the widespread use of natural gas and coal mining also brought the security of these two energy sources into the system of energy security. Eventually, electricity security was also included in the concept of energy security.