How to Convert Gas Units to kWh the Easy Way

Gas flame, unit calculator and energy savings

Although your gas supply is paid for in kilowatt-hours (kWh), your gas meter may actually record consumption in cubic metres (m3) or cubic feet (ft3). To get the most accurate business energy comparison and find a better deal, you'll want to know how to convert gas units to kWh.


How do I Convert Gas Units to kWh?

Whether running a business energy price comparison or simply trying to work out if your estimated bills are accurate, knowing exactly how much gas and electricity you use is key to getting the best value out of your energy deal.

Although both electricity and gas are priced in kilowatt-hours (kWh), your gas meter may actually measure your usage in cubic metres (m3) or cubic feet (ft3).

This can prove to be a real headache when trying to run a business energy supplier comparison, as you will usually be asked to provide your average energy consumption in kWh.

Fortunately, converting gas units to kWh is relatively straightforward. All you need to do to calculate kWh from m3 or ft3 is follow the respective steps below.

Metric gas meters: convert gas m3 to kWh

If your gas meter was installed after 1995, it is almost certain to be a metric gas meter. Metric gas meters will usually have the term ‘cubic metres’ or ‘m3’ stamped on their display, as in the image below.

Metric gas meter display

How to convert m3 to kWh

If your meter measures in cubic metres, the following calculation is used to convert m3 to kWh:

Cubic metres (m3) used x calorific value (usually 40.0) x Correction factor (1.02264) ÷ kWh conversion factor (3.6) = kWh

To convert gas m3 to kWh, follow these steps:

  1. Calculate the number of units used over a billing period. Take a meter reading at the start and end of this period.
  2. Subtract your first meter reading from your second reading to give the amount of gas used over this period.
  3. Multiply this number by the calorific value. Calorific values can vary slightly, but will be stated on your bill. As an average, we have used 40 megajoules per cubic metre as the calorific value in our calculations.
  4. Multiply this figure by 1.02264. This is the correction factor and accounts for temperature and pressure as gas expands and contracts.
  5. Convert this figure from gas m3 to kWh by dividing it by 3.6.

Seems simple enough, right? To give an example, let’s take a meter reading of 100m3 and convert it to kWh:

100(m3) x 40.0 x 1.02264 ÷ 3.6 = 1,136kWh

What is a calorific value?

The calorific value is the amount of energy released in a volume unit of gas. It is measured in megajoules per cubic metre. Your gas supply will typically have a calorific value of between 37.5 and 43.0 megajoules per cubic metre.

What’s the volume correction factor?

When converting gas units to kWh, the volume correction factor takes into account a property’s temperature, pressure, and atmospheric conditions. We’ve used 1.02264 in our calculations, as this is the most common value, though you’ll be able to find the exact number for your business premises on your gas bill.



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*Of customers who made a saving on a three-year business energy contract when switching through our trusted partner Bionic, the average amount saved was £1,305. Based on data between January 2020 and May 2020.


Metric gas meters: convert ft3 gas units to kWh

Although modern gas meters measure in cubic metres, there are still a large number of households and business premises with an old imperial gas meter, which instead registers gas consumption in cubic feet. An imperial gas meter can easily be identified as it will have the term ‘cubic feet’ or ‘ft3’ stamped on its front display.

Imperial gas meter display

How to convert ft3 to kWh

Converting gas ft3 to kWh is similar to converting gas m3 to kWh, with just one more step. To work out how many kWh have been used, we will need to first convert our cubic feet reading to cubic metres:

Cubic feet (ft3) used x metric conversion factor (0.0283) x calorific value (usually 40.0) x correction factor (1.02264) ÷ kWh conversion factor (3.6) = kWh

If you have an imperial meter measuring in ft3, you can take the following steps to convert gas ft3 to kWh:

  1. Calculate the number of gas units used over a billing period. You can do this by taking a meter reading at the start and end of this period.
  2. Subtract your first meter reading from your second reading to give the volume of gas used over this period.
  3. Convert this number from imperial (ft3) to metric (m3) by multiplying the units by 2.83.
  4. Multiply this number again by the calorific value. Calorific values can vary slightly, but will be stated on your bill. As an average, we have used 40 megajoules per cubic metre as the calorific value in our calculations.
  5. Multiply this figure by 1.02264. This is the correction factor and accounts for temperature and pressure as gas expands and contracts.
  6. Convert this figure from gas m3 to kWh by dividing it by a conversion factor of 3.6.

Again, as an example, let’s take a meter reading of 100ft3 and convert it to kWh:

100(ft3) x 0.0283 x 40.0 x 1.02264 ÷ 3.6 = 32,156kWh

As we can see, the final figure this time is 32,156kWh. If your imperial meter measures in hundreds of cubic feet rather than cubic feet, you should use 2.83 instead of 0.0283 when converting from imperial to metric in step 3 and 28.3 if it uses thousands of cubic feet. These higher units of measurement are usually indicated by the phrase ‘x100' or ‘x1000' on your meter.

How to get the best gas unit rate per kWh

Illustration of a gas flame and energy savings

Once you’ve converted your gas units to know your average consumption in kWh, you’re ready to compare business energy deals and see if you can get a better gas and electricity plan elsewhere.

You could save hundreds - or even thousands - of pounds just by changing your energy plan. In fact, customers who switch business energy suppliers with Selectra save an average £1,305* on their energy.

Switching supplier is fast, easy and free, and doesn’t require any digging or drilling, as your gas will continue to be delivered through your existing pipes. All you need to do is choose the best deal for your business and we’ll take care of the rest, including contacting your current energy provider and getting you set up with your new supplier. Speak to a business energy expert today on 020 3318 3633 or get a free online quote to find out how much you could save.

*Of customers who made a saving on a three-year business energy contract between January 2020 and May 2020, the average amount saved was £1,305.

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