Changing gas calorific value on bills

Richard_III_2

I've been looking through my last few BG gas bills.

In the conversion from gas units to kWh, can anyone explain to me what the calorific value is and why it changes.

My current bill states
When we work out your bill, we convert your gas units into kilowatt hours as follows: units used x [2.83] (for metric conversion - omit if your meter measures cubic meters) x vol conversion factor [1.02264] x calorific value [39.9000] divided by [3.6]

This is all well and good. But the calorific value has been changing over the last few bills.


19 Feb 2004 - 39.0000
23 Nov 2005 - 39.2000
8 Feb 2006 - 38.6000
16 May 2006 - 39.3406
25 July 2006 - 39.8842
now - 39.9000


Many thanks

espresso

See this thread where it has been discussed previously.

Hazzanet

It's the amount of energy derived from burning a set amount of gas. It changes depending on where the gas came from, its composition etc.

I believe they use an average figure across your supply area, and it does regularly change.

Hazza

Richard_III_2

whoops - must search forum / internet first

penrhyn

Natural gas is well, natural, and its composition will vary from time to time, ie the amount of methane, ethane, propane and butane etc. its composed of, and thus the energy a given volume produces.
The calorific value corrects for this variation.