The lower heating value (LHV; net calorific value ; NCV, or lower calorific value ; LCV) is another measure of available thermal energy produced by a combustion of fuel, measured as a unit of energy per unit mass or volume of substance. In contrast to the HHV, the LHV considers energy losses such as the energy used to vaporize water - although its exact definition is not uniformly agreed upon. One definition is simply to subtract the heat of vaporization of the water from the higher heating value. This treats any H 2 O formed as a vapor that is released as a waste. The energy required to vaporize the water is therefore lost.