How to read your gas invoice

Click on the link below for a sample invoice :

How to calculate your gas invoice

Meter Unit Conversion Factor


Thousands of Cubic Feet



Hundreds of Cubic Feet



Tens of Cubic Feet



One Cubic Foot



Hundreds of Cubic Metres



Tens of Cubic Metres



Tenths of Cubic Metres


Process to calculate your gas invoice

  1. To calculate the gas used, subtract the previous read from the present for each meter
  2. Multiply the figure by the Correction Factor (CF)
  3. To calculate the number of M3 used, multiply this figure by the Conversion Factor (shown below in the table and on the reverse of your invoice). Please ignore this part of the calculation if your meter is already measured in M3
  4. Multiply this figure by the Calorific Value (CV)
  5. Divide this figure by 3.6 to convert to kWh
  6. Multiply the number of kWh by the unit price to calculate the cost per meter
  7. Add together the cost of each meter to calculate the total cost, excluding VAT
  8. VAT is added at 20.0% unless any exemptions apply
  9. Apply CCL at a rate of 0.203 pence per kWh unless any reductions apply
  10. The sum of these calculations amounts to the Total Gas Sales 

Invoice Definitions


A after a meter reading indicates actual read taken by the data collector or agents working on its behalf


E after a meter reading indicates an estimated read


C after a meter reading indicates a read given by the customer


S after a meter reading indicates a read that has been agreed between two gas or electricity companies when the supply has transferred from one to the other

Kilowatt Hours (kWh)

This is the unit of measure for energy consumed

Climate Change Levy (CCL)

This is a government energy tax on Industrial and Commercial consumption, subject to VAT To calculate CCL multiply Total Consumption by 0.198p/kWh (reductions may be applicable)

Meter Point Reference (MPR)

A unique number that identifies the specific point of entry of the gas supply into the property

Correction Factor (CF)

A fixed meter specific factor applied to take into account the effect of temperature and pressure on actual gas flow. It is a legal requirement to include this factor in the calculation of our invoices.

Calorific Value (CV)

This represents the amount of heat or energy in a given volume of gas. An average calorific value is calculated monthly by the transporter and allows for any periodic or regional variations in the quality of natural gas. It is a legal requirement that we include this factor in the calculation of our invoices