Calorific value, also known as heating value or energy value, is a measure of the amount of heat released by a fuel when it is burned. It is usually expressed in units of energy per unit of mass, such as joules per kilogram (J/kg) or kilocalories per kilogram (kcal/kg).

For example, the calorific value of wood pellets is typically between 4.5 and 5.5 kWh/kg. This means that when one kilogram of wood pellets is burned, it will release between 4.5 and 5.5 kilowatt-hours of heat energy, depending on the specific type and quality of the pellets.

Calorific value is an important factor to consider when selecting a fuel for heating or energy production, as it can affect the efficiency and cost of the system. Fuels with higher calorific values generally provide more heat energy per unit of fuel and may be more efficient, but they can also be more expensive to purchase.