How to convert gas units to kWh.

Gas with calculator and pencil.

Why do I need to convert gas units?

Unlike your electricity, your gas supply is measured in either cubic meters (m3) or cubic feet (ft3). So you can know how much you’re using in kilowatt-hours (kWh), we’ll show you how to convert your gas usage.

This will enable you to check if your estimated bills are accurate as well as compare energy prices with accurate usage.

Do I have a metric or imperial meter?

First you need to check which type of meter you have, metric or imperial.

Imperial meters have four digit readings, not including the numbers in red/after the decimal point and measure your usage in cubic feet (hcf).

Metric meters have five or six digit readings (again not including the red numbers/decimals) and measure your gas usage in cubic meters (m3).

Depending on which meter you have, you’ll need to do a different calculation to convert your gas units to kWh.

Converting a metric gas meter.

If you have a metric gas meter then you’ll need to use the following formula:

Cubic meters (m3) used x calorific value x Correction factor (1.02264) ÷ kWh conversion factor (3.6) = kWh.

We’ve broken it down step by step for you:

  1. Work out how many cubic meters of gas you’ve used. You can do this by subtracting your current reading with your last billed meter reading.

  2. Multiply this number by the calorific value. You can find this on your bill.

  3. Multiply this figure by 1.02264. This is the correction figure which accounts for changes in the temperature and pressure of the gas.

  4. Divide this figure by 3.6 and you’ll have your gas usage in kWh.

As an example, if you used 100 cubic meters of gas and had a calorific figure of 38 then it would be:

100 x 38 x 1.02264 ÷ 3.6 = 1,079.45 kWh

Converting an imperial gas meter.

This is the same as the metric meter, with one extra step, you’ll need to convert the cubic feet into cubic meters first.

Most imperial meters record in hundreds of cubic feet (hcf) rather than single cubic feet.

To convert hundreds of cubic feet to cubic meters, you need to multiply your usage by 2.83 before you start step 2 above.

So if you used 50 hcf, the calculation would be:

50 x 2.83 x 38 x 1.02264 ÷ 3.6 = 1,527.4 kWh

If your imperial meter measures in cubic feet (which is unusual these days) then you’ll need to multiply by 0.0283 rather than 2.83. If it’s thousands of cubic feet then it’ll be 28.3. It can be quite difficult to tell from your meter which units it is recording in, so please get in touch if you're not sure.

What is the calorific value?

The calorific value is a measure of how much heat the gas creates when it burns. You could use this as a measure of the quality of the gas. The calorific value of your gas supply is generally between 37 and 43 megajoules per cubic meter and is shown on your energy bill.

To make sure they’re as accurate as possible, calorific values are tested continuously at various points throughout the National Grid gas network.

Need some more help?

Whether you're not sure how to read your meter or you want to check your gas usage on your online account, we've got you covered. Our energy jargon buster could also help simplify reading your energy bill.

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