We recently switched energy suppliers. The effective handover date was 13 November.
I've just checked the old account, which was in credit to the tune of £300-400 (probably more now) with Shell Energy, and it tells me that the refund will be paid 11 weeks after the process started.
They take 6 weeks from the final reading date before they issue the final bill, the wankers, and a further 2 weeks before they issue the refund. Given that we were billed monthly, I can't for the life of me see why they can't issue the final bill around what was the "normal" billing date, or at least a couple of weeks later.
They are an absolute shower of shite, continually over-estimating readings (and thus overcharging) despite accurate readings having been submitted (this was one of the reasons we switched). A few months ago, they decided they'd undercharged us, debited £1,700 approx to our energy a/c, and put our monthly payment up to nearly £400 for a small 2-bed house occupied by 2 adults. It took us 3 months to get that straightened out and the overpayment refunded.
God knows how many customers they supply, but if they hang on to an average of £400 of customers' money for 3 months a few times, they must have a very healthy bank balance.
Bunch of chiselling heisters, the lot of them.