Help with calculating British Gas - Gas kWh

dazzh

Hi,

Could anybody please help with the correct formula as to how British Gas calculate their Gas kWh. They do not include this on their bills so I emailed them and they state the following:-

• Present reading - Previous reading = Total Units Used
• Total Units Used x 1.02264 (Correction Factor) = Corrected Consumption
• Corrected Consumption x 2.83 = Cubic Metres 
• Cubic Metres x Calorific Value (given on latest bill) / 3.6 = Total kWh Used

I have tried this but missed out step 3, as my meter is in cubic meters, but always get less kWh than what they bill me for.

As an example one period was 127.7 units. So 127.7 x 1.02264(correction factor) x 38.3(calorific value for that period) / 3.6 = 1389.3kWh. However BG has calculated this as 1413kWh.

If it was a one off I probably wouldn't have bothered but it's repeated throughout all my gas bills. 

Any help greatly appreciated so I can chase this up with BG.

MikeJXE

The only difference in m3 to kWh is the calorific value that changes periodically 

Do yours match BG 

Unless they are using more decimal places like 127.7999

Conrad3000

They seem.to be making it as difficult and complicated as possible to the average person.

They might as well break down the bills via Calculus.

MikeJXE

I wouldn’t worry about it it’s only pence 

I keep a spreadsheet on my energy use every month, the only item I can’t calculate until I get the bill is the calorific value 

When thats in my calculations compared to Octopus are within a couple of pence but in the main spot on 

Gerry1

dazzh said:

As an example one period was 127.7 units. So 127.7 x 1.02264(correction factor) x 38.3(calorific value for that period) / 3.6 = 1389.3kWh.

Two likely variances here.

• The volume should have been 127m3 (you should ignore any figures after the decimal point or shown in red).
• The CV varies all the time.  It seems unlikely that the agent would have looked up the CV for your area and also calculated it for the exact date range of your billing period.

The simple answer is Ditch and Switch !  Octopus for example give a detailed analysis of the Volume to kWh calculation.

dazzh

Thanks to all for your replies.
I eventually phoned BG and explained the issue. The advisor tried to calculate it and got the same answer as myself so she's passed it through to another department to have a look and they will get back to me.
If I get a reply I'll update but I'm not too hopeful of hearing from them.  

Gerry1

It's quite possible that you and the agent were both using the current Calorific Value, but that's effectively just a snapshot: the CV may well have been higher during part of the billing period, especially if it was longer than one month.

If your car used 250 litres of petrol in the last three months and today’s pump price is 145.9p, you can't assume you spent exactly £364.75

dazzh

Thanks @Gerry1 but we used the calorific value from the bill for the period in question as I noticed that it varied throughout the billing cycle.
If they would just print how they calculate it on the bill it would be easier to understand. Instead they only give you the gas units used the calorific value and then the total kWh. Nothing about correction factor or how they arrive at your kWh.

MikeJXE

My Octopus explain the calculation thus on every bill