There's never been much sense in trying to work out by how much my electricity payments have changed with British Gas. They've had over thirty years to assess my average annual usage but they still keep putting my direct debits up really high for a few months and then dropping them really low for the next few months. Over the past few years, I've had payments of well over £200 per month taken from my account during some periods but well under £100 per month during others.
I'm currently paying £185 per month. The BG website says that I'm over-paying but I like it that way. I prefer to build up a nice healthy credit balance, so that I don't have to worry too much when I finally decide that it's time to turn some heating on.