The heating value (or energy 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.
Applicable units are those of quantitykind:SpecificEnergy
https://en.wikipedia.org/wiki/Heat_of_combustion
http://dbpedia.org/resource/Specific_energy
The heating value (or energy 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.