What's the equation to convert gas meter readings into kWh?

  • 16 March 2022
  • 9 replies

Does anyone have the equation to work out the KWH from a meter reading for both gas and electric. Please.


Best answer by nealmurphy 16 March 2022, 17:04

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9 replies

Userlevel 7
Badge +2

Hi @Johnnyhornet 

First the easy one. The electricity should be measured in kWh on the meter. So to work out how much you’ve used since the last reading you simply take the old reading away from the current reading on the meter.

Now for the trickier one (science books at the ready)…

Gas meters can measure usage in cubic feet or cubic metres. If yours is measured in cubic feet then multiply the value by 0.0283 to get cubic metres.

The volume of a gas is dependent upon pressure and temperature and therefore varies. The volume of gas measured by the meter is adjusted by multiplying by a correction factor to take account of the temperature and atmospheric conditions. The correction factor used will be shown on your gas bill (e.g. 1.02264).

Next, the volume needs to be converted into a calorific value (CV) which is a measure of the energy released when a given volume of gas is completely combusted. This depends upon the gas’s composition. The CV usually ranges from 37.5 to 43.0 MJ per cubic metre. The value used should also be on your bill.

Finally. the thermal energy can be converted into kWh. 1 Watt is 1 Joule per second. 1 Joule is 1 Ws. 1 kWh is 1000x3600 Joules = 3.6 MJ.

So divide the CV by 3.6 to convert MJ into kWh.

There will be a test next week, so don’t forget to revise.


Many thanks

Please help to understand this readings.
Our meters are reading in meters cub but we pay for KW 
How the meters cub are converted in to the KW and how much is actual a unit that is read on the meter.

Userlevel 6
Badge +3

This website has a conversion calculator

I am interested in solar panels at the moment so am looking to work out kwh usage.  I can calculate kwh and make and estimate for the CV.  But I cant for the life of me get a value near what my usage is calculated at by OVO  How can I find out whether OVO have my gas metre readings as a cubic metre or cubic foot measurement?

Userlevel 7
Badge +1

Hey @Gertie !

I can help with that. If you don’t mind, please can you post photos of your gas meter? I’ll need to see it in order to figure this one out. :)

Its a cubic foot meter Apparently listed as imperial meter. No. 021005

Userlevel 7
Badge +1

Assuming that’s a meter reading, I calculate roughly 664988.1877 kWh. But this isn’t going to be perfect as I don’t have the exact formula to hand.

Userlevel 7

There’s a site I’ve found that offers this service, @Gertie - theenergyshop have a page for this here


Can I ask what other factors you’re looking at when looking into solar PV panels in your home? Need advice from our solar panel members?