the future price of electricity, part 3

So, in June I blogged a follow-up to the weird estimate npower gave for my future electricity bills. Two months later, and I've had my next quarter's bill (differently weird, there).

The estimate seems to have gone back to a more reasonable amount this time around, so I'm no longer fearing an order of magnitude increase in power bills. I wonder what caused the original glitch?

But I'm going to keep a close eye on these estimates in the future.