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kWh, m3: what units are used to measure gas?
On a meter, gas consumption is displayed in cubic metres (m3), whereas it is indicated in watts-hours (wH) on bills from energy suppliers. What is the difference?
The cubic metre summarises the volume of gas that has passed through the pipelines, whilst the watt-hour corresponds to the energy. This is why the watt-hour, and more commonly the kilowatt-hour (kWh) is used to bill gas and to provide energy statements.
The watt-hour is used to give the amount of energy present in cubic metres of gas. The Transport Grid Managers (GRT) determine the equivalent cubic metres - watt-hours daily using a number of parameters that influence energy:
altitude: the higher we climb, the greater the drop in atmospheric pressure and the less dense gas becomes,
the pressure demand during delivery: big gas consumers such as industries are supplied with a much higher pressure than private individuals,
the calorific value of gas: this varies constantly over time, principally as a function of the gas source, and is measured daily at different points of the French gas grid.
The watt-hour (wH) should not be confused with the watt (W), which measures the energy and which determines the power of an electrical device. 1 kilowatt-hour (kWh) corresponds to the energy consumed by a 1,000 watt device (i.e. 1 kW) over one hour.
