Your bill is based on the amount of energy you use, measured in gigajoules (GJ). Depending on your meter type, the usage is measured by volume in cubic feet or cubic meters. This gas volume measurement needs to be multiplied by a conversion factor to give us the energy used in gigajoules (GJ).
The energy or heat content of natural gas varies because natural gas has minor variations in the amount and types of energy gases (methane, ethane, propane, butane) it contains: the more combustible gases in the natural gas, the higher the GJ value.
FortisBC uses the Higher Heating Value (HHV) of the natural gas in the conversion formula. The Higher Heating Value (HHV) can be defined as the total heat obtained from combustion of a specified amount of fuel and its stoichiometrically correct amount of air, both being at 60°F when combustion starts, and the combustion products being cooled to 60°F before heat release is measured. Natural Gas is sold on the Higher Heating Value (HHV) basis.
By contrast, the Lower Heating Value (LHV) is the Higher Heat Value (HHV) minus the latent heat of vaporization of the water vapour formed by the combustion of the hydrogen in the fuel. A “rule of thumb” for natural gas is HHV = LHV x 1.11.
The heating value of the gas being supplied to FortisBC on your behalf varies daily and is constantly measured. For a copy of daily Higher Heat Value data (HHV) for all areas of the province, please download the following file:
- Heat Content Values (1 MB)
*File updated to July 31, 2014
Not sure what your zone is? Consult our Town to Energy Zone Cross Reference Chart (19 KB) to find out.