My gas bill.

[Workingman]

I bet that I am not alone in thinking that the units of gas used times the cost in pence per kWh would be the price I pay. How wrong was I?

I did that calculation and my bill was nearly half what SP was telling me it came to, so I queried it. After a very long chat with a customer advisor who couldn't help I went and did some digging.

The units of gas you use are measured in cubic metres not kilowatt hours - there is an equation to use and it is this: units used x 39.24 (calorific value of the gas) x 1.02264 (variable for the calorific value) / 3.6 to bring it to kWh. You then have to multiply that value by the kWh price quoted. It looks a bit frightening, eh? No wonder the calculation is hidden deep in the bowels of every energy supplier website.

It is actually not as bad as it looks. The x 39.24 x 1.02264 / 3.6 part is in numbers so small that they give a constant to all intents and purposed. It is 11.15.

So your bill is units used x 11.15 x the pence per kWh.

A simple bill would be 20 units x 11.15 = 223 times that by say 7.5 pence per kWh and it is £16.73p. You then have to add a month's service charges to get your true bill. It is worth keeping an eye on (and records of bills) especially if you sometimes get estimates.

Only works for gas as electricity is already metered in kWh.

[TheOstrich]

The 39.24 (calorific value of the gas) figure is variable, month by month, between 39.2 and 39.4.
The actual figure they've used is set out on each bill, (in the blurb on page 2 in E.On's case).
Only makes pence difference, but it does tend to beggar up my carefully-worked spreadsheet !

Our gas bill's coming down now we're into better weather. Last month it was just £1.01 a day.
The electric's running at around £1.90 a day (£699/year), and that doesn't tend to vary much throughout the year.

[Workingman]

Only makes pence difference, but it does tend to beggar up my carefully-worked spreadsheet !

Mine too, which is why I use the 11.15 constant to calculate the amounts and then enter the actual bill manually in the spreadsheet - not more than a few pence out - I checked my back bills. I am now paperless so do not get all the calculations. I input my reading and the website calculates the bill.

It just bugged me that the calculations are so hard to find.