HHV conversion factors

'Heating values'

'Heating values' (or 'calorific values') are measures of the amount of energy contained within a given quantity of fuel. Heating values are therefore expressed in terms of energy per mass or energy per volume of fuel - e.g. GJ per t, kWh per L.

Heating values allow the conversion of fuel quantities into their corresponding quantity of energy. This can be useful for expressing emissions factors in terms of energy consumed, and therefore making emissions calculations on the basis of energy consumption rather an actual physical quantity of fuel.

Calorific basis

The quantity of energy contained within a fuel can be considered in two ways. The total quantity of energy is indicated by the higher heating or gross calorific value. A second measure of energy content discounts the energy which is required to vaporise any water contained within the fuel and therefore not realised as heat. This latter measure is represented by the lower heatng or net calorific value.

Where no explicit data is available, a conversion between higher and lower heating values can be made following IPCC and Greenhouse Gas Protocol advice, as follows:

Lower heating value = Higher heating value x 1.05; for solid and liquid fuels

Lower heating value = Higher heating value x 1.11; for gaseous fuels