The energy value of coal, or fuel content, is the amount of potential energy coal contains that can be converted into heat. This value can be calculated and compared with different grades of coal and other combustible materials, which produce different amounts of heat according to their grade.
While chemistry provides ways of calculating the heating value of a certain amount of a substance, there is a difference between this theoretical value and its application to real coal. The grade of a sample of coal does not precisely define its chemical composition, so calculating the coal's actual usefulness as a fuel requires determining its proximate and ultimate analysis (see "Chemical Composition" below).
