calorific value

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The calories or thermal units contained in one unit of a substance and released when the substance is burned.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The amount of heat produced by the complete combustion of a material or fuel. Measured in units of energy per amount of material, e.g. kJ/kg.
• noun The amount of energy available from an item of food when digested, mostly from carbohydrates and fats