Anyone receiving a recent electricity or gas bill will have noticed the substantial price rises. Many of these bills are estimated which isn't usually a big problem, but, in this instance, if the bill is under-estimated it could be losing you money. This is because when you catch up with the higher useage it will be charged at the new prices, rather than the old price that was in force when the power was used.
In my case, the useage was considerably under-estimated on my recent bill. I've rung them up and given them an accurate reading. If I had left the inaccuracy to carry forward it would have cost me over £30 more because of the price hikes.