Ever wondered why your gas bill is so high?

[Andy Wade]

There are actually up to *four* "conversion factors" which are now being confused in this thread:

1. Imperial to metric conversion: since 1992 all gas bills have been based on usage in cubic metres. As most gas meters still read in "units" of a hundred cubic foot the metered consumption (difference between the "current" and "previous" readings) is multiplied by 2.83 to convert to cubic metres. This conversion factor is constant, and clearly does not apply if you have a metric meter, which reads directly in m^3.
2. The volume conversion factor or VCF. This is a constant multiplier with a value of 1.02264 and is an adjustment for temperature and pressure. The VCF was first introduced during 1997 along with a corresponding reduction in the gas price. I'd be interested if anyone knows the detailed reasons for its introduction, but its existence seems to be an admission that metered gas volumes had previously been slightly low - presumably because the temperature and pressure at which meters are calibrated don't quite match actual supply conditions.
3. The calorific value. This is the energy content of the gas and is the only factor which varies from bill to bill. The value used is a legal "declared" value of the fuel's gross calorific value (GCV) in units of megajoules (MJ) per cubic metre.
4. Conversion from megajoules to kilowatt-hours. Gas is priced in kilowatt-hours (kWh) so the calculated energy consumption is next divided by 3.6 to convert from MJ to kWh.

So, for an imperial meter, the billing calculation is essentially

charge = (current - previous) * 2.83 * 1.02264 * GCV * price / 3.6

or, for a metric meter,

charge = (current - previous) * 1.02264 * GCV * price / 3.6

then add VAT at 5%.

[Jake D]

I would imagine it is only a tiny percentage of the said terraced houses that are wasting loads of gas or not using any gas. And the two extremes found in that tiny percentage, would to a large extent cancel each other out, no?

Perhaps I should rephrase my question and ask for the mean rather than the average.

Jake D

[lairdy]

We are not worthy ;-)

I hadn't realised the volume conversion factor was a constant. And was mixing it up with the calorific value, which is variable (by up to 15% I found, surprisingly - probably due to the %age of C2 and higher hydrocarbons).

[Jake D]

Thanks for clarifying that one.

Transco recently came to my house offering to rip out my old (circa

1980) meter and replace it with a modern one - free of charge. They said they were doing this for all households with old-style meters. I was unable to take them up on the offer at the time, since I had 'work in progress' in the room concerned. But it gave me time to wonder why they were wanting to change the meter. Obviously it's going to cost them something. I wonder what they stand to gain from this considerable expense. I wonder if I'm better off letting them change my meter, or better off keeping the old one!

Jake D

[Tony Bryer]

Check out

- it will give you a cost in £ and a price per kWh. A bit of reverse calculation will turn this into kWh/year and your gas bill will give you the conversion to volume

[manatbandq]

If you are one of the ones in the minority then the average wouldn't be much use to you.

The mean is the average in the sense you are using the terms. For what you are asking you probably want to use the mode (most common value).

MBQ

[manatbandq]

It's cheaper for them to have a team change many meters in the same area than to have to keep coming back to individual meters with the complication of missed appointments, etc.

MBQ

[Jake D]

I believe I should be very roughly typical regards gas consumption for a terraced house in Southern England.

Ah, yes, thanks; the mode! I had forgotten that one! Okay then, the mode is what I'm after.

I just want to determine whether my gas bills seem realistic. If not, then I shall suspect a gas leak somewhere. My gas consumption seemed to rise inordinately some time last Winter (more than usual).

Jake D

[Jake D]

That looks useful - thank you.

Jake D

[Guy King]

The message from Jake D contains these words:

The midrange or mode or even median might be of more use.

[Tony Bryer]

If only they worked that way here: six meters in the common front hall, being replaced one by one. When I queried this, the fitter said that he was over at one of the big 1930s block in East Sheen every couple of weeks to change another meter and he'd be doing this for another year.

It could be that the replacement algorithm is by usage, account age or somesuch. Or it could be that they don't trust the fitters not to get muddled if faced with replacing more than one.

I've had two visits to change my gas meter so far, both abandoned because the meter (as was the fashion) hangs from the pipes and they can't change this without moving a pipe ... which meter replacers are apparently not competent to do.

[Andy Wade]

15%? My record of gas bills going back to 1991 shows a lowest CV of 38.1 MJ/m^3 and a highest of 39.6. That's a spread of just under 4%.

[<me9]

Both my gas and electricity meter were changed about 10 years ago, as they were older than what was allowed. Both were new when the house was built in

1976. The electricity meter was replaced by one dating from 1953 (but presumably recalibrated). As the meters are the property of the supplier (or is it the distribution Co.?) I doubt if you have any say in the matter.

One of my beefs with BG is that at one time they insisted on changing the meter (cos it was inconsistent in readings and they suspected fiddling? the previous occupier worked away for long spells). I had to leave the key with a neighbour, and when I returned there was a strong smell of gas due to a cracked fibre washer on the new meter. Safety experts begorra!

[manatbandq]

Turn everything off for a few hours and check the meter before and after.

MBQ

[LJMeek]

A colleague in work and my sister-in-law have just found out they've the same billing problem as me. I know it's not statistically robust, but I've only asked 8 people to check if their meter units tie with their billing units. That's 2 out of 8. I posted the original message to see if I could get a response from a wider sample of gas users. Maybe this isn't a national problem after all.

[Jake D]

Excellent idea! Thanks. (Why didn't I think of that?!?)

Jake D