Gas and electricity bills in the UK are set to rise by up to £206.72.
That’s because 26 fixed dual fuel tariffs expire at the end of January, according to price comparison site Gocompare.com.
It warns 22 of those tariffs will result in higher bills if customers are rolled onto their suppliers’ variable tariffs.
That could be an average annual rise up to £258.26 on their energy bills.
However it added, customers with tariffs from M&S Energy, First Utility and Scottish Power will see their bills fall slightly when their tariffs expire.
This is because the suppliers’ standard variable tariffs are cheaper than the fixed deal they are currently on.
However, these customers can only expect to save between £4.22 to £29.30 depending on their provider, it added.
Ben Wilson, energy spokesperson for the site said: “There are some really competitive energy available at the moment so you could be doing yourself a disservice if you let your supplier roll you onto their standard variable tariff without shopping around first.”