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Calculating your costs
Before you can calculate the cost of your electricity and gas consumption, you will need to know what your tariff (the amount you pay for every kilowatt hour) is. You will find the specific name for your tariff on your fuel bill or your annual statement. Alternatively, you can phone your supplier to ask. Depending on the type of tariff you have, you will usually have a standing charge to pay along with the cost of your ongoing fuel use. This will also be shown on your bill and annual statement as a daily charge.
For gas consumption, you need to check your meter to see whether you have an old imperial meter or a newer metric meter. If it is an imperial meter measuring gas in cubic feet, it will usually have the words ’cubic feet’ or ’Ft3’ shown somewhere on the front of the meter. If it is a metric meter measuring gas in cubic metres it will usually show the words ’cubic metres’ or ’M3’.
Your tariff for gas will be in kilowatt hours (kWh), so the readings from your gas meter need to be converted into kWh, so that you can then work out how much the fuel you use is costing. You can do this by:
    multiplying units used by 2.83 to give the number of cubic metres of gas used (if the meter is a newer metric one measuring gas in cubic metres this part of the calculation is not needed);
    multiplying by the temperature and pressure figure (1.02264);
    multiplying by calorific value (approximately 39.5, though the exact calorific value can be found on a gas bill);
    dividing by 3.6 to get the number of kWh.