The heat of combustion for fuels is expressed as the HHV, LHV, or GHV: Heating value is commonly determined by use of a bomb calorimeter. It is measured in units of energy per unit of the substance, usually mass, such as: kcal/kg, kJ/kg, J/mol, Btu/m³. The calorific value is a characteristic for each substance. The heating value or calorific value of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. 3 Lower heating value for some organic compounds (at 15.4☌).
