How do I calculate my gas meter readings to kWh?

OhWow

I'm trying to work out my yearly gas usage in kWh, but can't find the calculation.

My meter has CUBIC FEET written by the numbers.

My reading on 1 October 2026 was 189. On 1 October 2025 it was 134.

Thanks

MikeJXE

this is what our friend Google says

elsien

alternatively, just use one of the online calculator. Your energy provider probably has one.

StewedApple

https://forums.moneysavingexpert.com/discussion/6685605/how-do-i-calculate-my-gas-meter-readings-to-kwh

You will find the formula used on your most recent gas bill. It seems to vary slightly as its based on energy value in gas (which apparently varies), pressure, where you are (because the gas may be from different sources) possibly time of year and also whether it's a leap year (this last one may not be true).

I also understand from other people's comments that there is no such thing as kWh but it is useful shortcut.

debitcardmayhem

Perhaps look at your bills , they bill in kWh

PA1968

I use this site for checking the CV values against my bill - regions can be changed

https://fprates.online/gas/NW

Scot_39

From memory not all suppliers give the full calculation.

Like in this example guide on how to read your bill from British Gas. The assumed m3 in equation is there in the text, but not on the example bill.

https://www.britishgas.co.uk/help-and-support/bills-and-payments/view-your-bill

Maybe its bills are different if you have an old meter in ft3 etc.

Of course it would help if the example actually used the readings for the date of the bill - and not months earlier - as the readings change shown is 70 from Aug to Nov - but the bill is 43 gas units Jan Feb at 40 calorific value.

And the 43 magically becomes c490 kWh - the metric factor.

What after all is a "gas unit"

And not no mention of m3 or 100 ft3 or volume factors changing with meter age.

But too many people report are misbilled on unit factors - so either they dont read their bills - or as above - I suspect the bills dont make it clear enough what units the calcs are using.

Perhaps because the presumption is that we now all have m3 meters.

But given some of the complaints have been people overbilled after smart upgrades (all m3) I find it a little shocking that they don't have to be far more explicit - like clearly highlight the units presumed in the calcs they apply.

molerat

Ballpark for an imperial meter is 100 cu ft (meter units) = 32 kWh (billing units). The fly in the ointment is that one of the factors in the conversion, the calorific value of the gas, varies on a daily basis and is (should be !) averaged over the billing period. This figure can be downloaded from the National Gas Transmission Data Portal and used in your own calculations if you so wish. The fprates site linked above also gives that figure and will give the average for any selected period.

Your use is roughly 189 - 134 = 55 x 32 = 1760 kWh.

Ildhund

@molerat wrote:

… the calorific value of the gas … varies on a daily basis and is (should be !) averaged over the billing period.

I'm not sure that's the case. If daily readings are available, then it would be proper to use each day's CV to convert quantity of gas consumed to kWh. If actual readings are some days apart - e.g. at the start and end of a monthly billing period - then yes, the prescribed average of daily CVs should be used.

This is the official word on converting gas volume to kWh: Gas meter readings and bill calculation - GOV.UK. The legal basis is The Gas (Calculation of Thermal Energy) Regulations 1996

molerat

https://forums.moneysavingexpert.com/discussion/comment/82158558#Comment_82158558

OFGEM issued a letter to suppliers in 2014 clarifying how the regulations were to be interpreted and it stated that the truncated average over the billing period was to be used. One particular supplier uses a "daily billing period" but provides no calculations for that and presents a monthly bill showing that truncated average so the figures do not add up and states the figures are "only an indication" of how the bill was calculated. The daily calculation method also leaves scope for re-billing as the daily CV can be resubmitted some time after the event so the final days of the billing period can be adjusted after the bill has been generated. Using a longer billing period would need a substantial change in a daily CV to make any difference to the truncated average.

FreeBear

https://forums.moneysavingexpert.com/discussion/6685605/how-do-i-calculate-my-gas-meter-readings-to-kwh

Depending on who your supplier is, there may be a graph on their web site showing historical usage - Octopus allows me to display daily, weekly, monthly, and yearly usage. The bill also states an annual estimated usage which isn't too far off what I've used in previous years. But if you are needing accurate kWh numbers to check billing, web graphs & forecast usage isn't going to be accurate enough.

Oh, and when you eventually get a new gas meter fitted (smart or dumb), keep an eye on your bills and make sure your supplier is charging you for cubic metres and not (100s)cubic feet.