gas formula to work out your gas bill

nudge51

I wonder how many of us look at the formula that british gas use to work out the units you have used to turn it into kw.
One component of this formula is something called the calorific value.

I noticed that this calorific value was different when I compared 2 bills
and was told by BG this does change but could not tell me why.

To me a "formula" is something that does not change,but I noticed that
the 2 bills I am comparing were 1st bill was at the higher price for the gas the 2nd bill was when they had reduced the price per kw but this bill was the one with the increased calorific value.

This has led me to believe they announce price cuts but then increase this calorific value in the "formula" to probably get you paying what you would be paying before so called price cuts but this is probably something we don't notice or even bother to check.
If anyone knows why this calorific value changes I would be interesed to know

jrrowleyws

Calorific values are regularly measured and you are billed based on an average. The calorific values vary depending on the composition of the gas. This is one reason you are not billed in units.

melbury

Can't we just be told what the price of 1 unit of gas is rather than having to work out this long forumula?

macman

For the reason already give-a 'unit' of gas (which can be a cubic metre or 100 cu ft, depending on your metering) is not a constant in terms of energy. The energy value, which is what you are billed on, varies, hence the calorific value adjustment having to be applied during the conversion to kwh, which is the actual billing unit.
You are not ever billed in 'units' as read from your meter-they are simply a measure of volume, not energy.
In practice, the variation in calorific value is minute, and makes a minimal difference to your bill.

whowants2brich

If you pick two rooms in your house, the bathroom and the living room. If you imagine how much oxygen and water is in both rooms, you'll probably find the bathroom has more of both than your living room, because you'll have an air extractor fan or vent in the bathroom, and central heating in the living room.

If you were to now say that the two rooms were the exact same size, they would contain the same amount of air. But the bathroom would contain significantly more water and oxygen in the air than the living room.

Your gas meter measures the volume of air/gas that passes through, in cubic metres or cubic feet. It does not know how much gas (the fuel) is actually in the gas (the air), and that is what is measured on a regular basis. It changes based on temperature, pressure, and various other parameters.

The calorific value is therefore adjusted to take this into account. And for the record, I just multiply my gas meter readings by 11.15, and find it is pretty accurate. It gives me a very rough guide to how much I've used, and is never too far out. The bill we got for the past 4 months actually had a conversion factor of 11.164 (by the time I multiplied and divided as per the formula)...

victor2

The Calorific Value of gas is published by National Grid for each of the regions in the UK on a daily basis and can be seen at http://marketinformation.natgrid.co.uk/gas/DataItemExplorer.aspx
In reality, it doesn't vary much and suppliers in my experience use a value for your bill which is a little below the mathematical average for the period billed.