In the UK the utilities take money to meet an estimated bill; meaning most people are usually creditors to the utility. If a customer doesn't rein it in then the utility will often take stupid amounts to meet an anticipated bill.
I think they were threatened with regulation and so stopped being so blatant, but they make money off holding customer's cash.
The projection is roughly the monthly consumption from last year if I am not not mistaking. You should change provider if you're being charged stupid amounts.
The provider certainly allows debt when moving in, while the contracts and payments are setup. Afterwards, I am not sure if the last bill if for the next or past period, probably a bit of both.
I think they were threatened with regulation and so stopped being so blatant, but they make money off holding customer's cash.