When reading your gas meter, the first thing that you need to do is identify that type of meter that you have. There are two main types of gas meter:
Metric Gas Meters
These are the most common and newest type of gas meters in the UK. These measure gas consumption in Cubic Metres (M3). On this type of meter, ‘Cubic Metres’ or ‘M3′ will be written on the display.
Imperial Gas Meters
This is the old type of meter and no longer very common in the UK, however some properties do still have imperial gas meters. These measure gas consumption in Cubic Feet (ft3). On this type of meter, ‘Cubic Feet’ or ‘ft3′ will be written on the display.
Important: Your gas meter does not directly display the number of units of gas that you are charged on your bill. Your gas meter displays the amount of gas consumed in either Cubic Meters (m3)of Cubic Feet (ft3) (depending on your meter type). This amount is then converted into ‘units’, measured in kilowatt hours (kWh’s). This conversion is done on your energy bill where you will then be charged an amount in pence per unit (kilowatt hour) of gas that you have used.
Step 1 – Calculate the Number of Cubic Metres of Gas Used.
The first step is to calculate the number of cubic meters used in the bill period. This is done by subtracting your previous gas meter reading from your current gas meter reading. This process varies depending on whether you have a metric of imperial gas meter.
Metric Gas Meter
- Gas Meter Reading on 10 Sep: 07707
- Gas Meter Reading on 10 Oct: 07744
- 07744 – 07707 = 37 Cubic Metres (M3) of gas used
Imperial Gas Meter (Must be converted to Cubic Metres)
- Gas Meter Reading on 10 Sep: 5148
- Gas Meter Reading on 10 Oct: 5163
- 5163 – 5148 = 15 (in hundreds of Cubic Feet of gas used)
To convert to cubic metres, multiply by 2.83. (Most imperial meters are in ‘hundreds of cubic feet’. If your meter reading is in ‘cubic feet’, then multiply by 0.0283)
Therefore 15 x 2.83 = 42.45 Cubic Metres Used
Step 2 – Multiply by Correction Factor (x 1.02264)
The number of Cubic Metres used is then multiplied by a Correction Factor (Correction Factor is always: 1.02264). The correction factor is applied to account for fluctuations of gas temperature and pressure in the UK.
Step 3 – Multiply by Calorific Value (x Variable – See Gas Bill)
The figure is then multiplied by the ‘calorific value’ which is a measure of the available heat energy of the gas. Calorific value varies, with the figure that is quoted on your energy bill demonstrating an average of the gas supplied to your property.
Calorific value is quoted in ‘Megajoules per cubic metre’ (MJ/m³), and may typically measure around 39.3 MJ/m³, however regulations state that Gas Transporters must must maintain a Calorific Value of between 38 MJ/m³ and 41 MJ/m³.
Step 4 – Convert to Kilowatt Hours (÷ 3.6)
The figure is finally converted to Kilowatt Hours by dividing by 3.6.
Step 5 – Multiply number of kilowatt hours (units) of gas used by the Unit Rate
The Kilowatt Hour figure that we have calculated can be multiplied by the Unit Rate to work out the chargeable amount.
See the full equation below to convert the number of Cubic Metres of Gas used into kilowatt hours (kWh’s):
‘Cubic Meters Used x Correction Factor (1.02264) x Calorific Value (Variable) ÷ Kilowatt Hour Conversion Factor (3.6) = Kilowatt Hours’
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