Converting gas units to kWh


Frequent Poster
From looking at my gas bill the meter readings appear to be in cubic metres.

This is then converted to kWh.

The conversion factor varies from bill to bill. In October the conversion factor was 11.3911 while in August it was 11.1042.

Surely the conversion factor from cubic metres to kWh should not change.

Can anyone explain why it varies?


Frequent Poster
The amount of kWh in a cubic metre of gas depends on the composition of the gas and this varies slightly all the time

From Energy Regulator website
Conversion Factor:
The conversion factor is used to convert the volume of gas used (m3) into the energy value of the gas (kWh). The conversion factor changes based on the energy content of the gas in the network. The energy content of gas may change depend on where it comes from, this is why there may be differences in the conversion factor from bill to bill. Gas Networks Ireland are responsible for calculating the conversion factor and they pass this information on to suppliers who use it when calculating customer bills.

From Gas Networks Ireland website

A natural gas meter measures the amount of gas consumed by all the gas appliances in a premise. The gas used is measured in cubic meters or cubic feet. However, your gas supplier must bill you on the basis of energy used i.e. kilowatt hours (kWhs). For domestic gas usage a conversion formula is used to convert cubic meters or cubic feet into kWhs. This conversion formula has been approved by the Commission for Regulation of Utilities. The conversion formula can vary nationwide. The formula depends on the local temperature, pressure and calorific value of the gas.

Factor used to convert the usage calculated between an opening and closing meter read from cubic meters (if metric meter) to kilowatt hours - components of the factor allow for pressure, temperature, compressibility and Calorific Value (CV).

Calorific Value is a factor used to calculate the energy equivalent of gas usage (The ratio of energy to volume measured in mega joules per cubic meter (MJ/m). Natural Gas is now obtained from multiple sources, so the CV changes on a daily basis and is calculated on the average daily usage over a billing period.

The method of calculating CV rests with Gas Networks Ireland, is in line with best international practice and has been approved by the CRU. CV is the amount of heat released when a mass of fuel (e.g. Natural Gas) is burned.

Please do not hesitate to contact your gas supplier should you require any further assistance regarding this matter.