How to convert gas units into kWh

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Convert cubic meters of gas to kWh

If your household uses gas for energy, you’ll have one of two types of meter: an imperial meter or a metric meter. Imperial meters record consumption in hundreds of cubic feet (100ft cubed) while metric meters record consumption in cubic meters (m cubed).

However, you would have noticed that you pay for gas using a price per kilowatt hours (kWh). This is because your supplier converts the readings from your gas meter to kWh in order to calculate your bills. 

While your supplier will do these calculations for every bill – and there should be information on the bill itself to explain how it’s been calculated – doing these calculations yourself is a useful way of making sure your supplier is billing you correctly for the type of gas meter at your property. If your numbers don’t match the numbers your supplier uses, you can query your bill with them.

Reading your gas meter

The first thing you’ll need to do is read your gas meter. When reading your meter, read from left to right and ignore any numbers in red.

To determine the number of units you’ve used this month, deduct the reading you’ve just obtained from the reading in your previous bill. As a simplified example, if your meter currently reads 150 and your previous bill read 50, your meter reading for this month will be 150 – 50 = 100. This means you’ve used 100 units of gas this month.

Converting gas units to kWh

Before you can convert gas units to kilowatt hours, you’ll need to first determine whether you have an imperial or metric gas meter. Usefully, your meter should have either ft3 or m3 next to the reading to indicate the unit of measurement used. Some meters may instead use the words ‘cubic feet’ or ‘cubic meters’ or the letters ‘Ft’ or ‘M’.

Once you’ve determined the type of gas meter at your household and taken a reading, you can follow the steps below to convert gas units to kWh:

Imperial gas meters

  1. Calculate your reading as explained in the section above.
  2. Convert from imperial to metric by multiplying the units by 2.83.
  3. Multiply by volume correction factor (1.02264).
  4. Multiply by calorific value (40.0).
  5. Divide by kWh conversion factor (3.6).

For metric gas meters, simply omit step 2.

If your imperial meter measures in cubic feet rather than hundreds of cubic feet, you’ll need to use 0.0283 for step 2 rather than 2.83. If it uses thousands of cubic feet, you’ll need to use 28.3 instead. Your meter will usually say ‘x100’ or ‘x1000’ to indicate the higher units of measurement.

The volume correction factor is used to take into account the temperature, pressure and atmospheric conditions at a property. This factor is typically 1.02264 unless your household has unusual atmospheric conditions. You can usually find this number on your gas bill. 

A calorific value (CV) is a measurement of the amount of energy contained in gas, measured in megajoules per cubic meter (MJ/m cubed). The CV of the gas at each Local Distribution Zone is continually measured by the National Grid who sends this figure to your gas supplier, who then uses it for their calculations. Typically, a gas supply has a CV between 37.5 and 43.0 MJ/m cubed. You can use 40.0 as a default number if you don’t have the exact figure.

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