To be able to convert the meter readings for gas from m³(n) into kWh (energy), a conversion factor is needed. The conversion factor used is the higher calorific value.

The higher calorific value of the gas is expressed in kWh/Nm³. One of these is defined per aggregated reception station.

The higher calorific value is equal to the quantity of heat that is released when 1m² (n) of gas is fully combusted under a standard atmospheric pressure of 1.01325 bar.

The initial temperature of the fuel-oxidant mix and the end temperature of the combustion products stand at 25° Celsius.

The calorific value is high (higher calorific value) when the water in the combustion products turns liquid.

The calorific value is low (lower calorific value) when the water in the combustion products remains as vapour.