Gas and electricity bills will rise by £147.95 as 12 dual fuel tariffs expire at the end of October.
According to a comparison site, householders will face a 15.22% rise in their energy bills if they allow themselves to be rolled onto their supplier’s standard tariff.
Npower, Co-operative Energy, Scottish Power, Sainsbury’s Energy, Extra Energy and First:Utility dual deals are expected to expire on 31st October.
It added customers on Extra Energy’s Fresh Fixed Price Oct 2015 v2 and ValuePlus Fixed Price Oct 2015 v1 tariffs could see an average increase at the end of the month of £186.08.
Caroline Lloyd, energy spokesperson at Gocompare.com, said: “The 12 fixed dual fuel tariffs due to expire on Halloween could result in a substantial price rise for customers on those tariffs. As such, people are really doing themselves a disservice if they let themselves get rolled onto their supplier’s standard tariff.
“Households need to fight back against what is effectively an automatic price rise, and the best way that they can do this is by getting online and shopping around for a better deal.”