Following recent price increases from the '˜Big Six' energy suppliers in the UK, MoneySuperMarket has warned that millions of Brits could fall victim to further rises as their fixed-term energy deals come to an end.
In order to combat this, the price comparison site recommends that customers act now and lock into another fixed deal, whether that's with a new supplier or their existing one.
A total of 84 fixed tariffs will end between now and 31 July, leaving millions of customers at risk of being automatically rolled onto their supplier's default tariff - which is usually most expensive - unless they take action.
Four of the so-called '˜Big Six' - British Gas, EDF Energy, Npower and Scottish Power - as well as some smaller suppliers - Co-operative Energy, First Utility, PFP Energy and Sainsbury's Energy - are among those with fixed tariffs ending between now and the end of July.
In fact, 52 fixed tariffs are due to expire at the end of June, with a further 32 coming to an end in July.
Once a fixed tariff deal comes to an end, energy suppliers will often automatically move customers onto a standard variable rate, or default tariff, meaning those affected could see their bills rise by more than Â£3001 on average, with little notice from their supplier.
Energy bills are set to rise
This is in addition to the 10.6 million Brits on average already impacted by hikes from British Gas, EDF Energy, Npower, E.ON, Scottish Power and, most recently, SSE last week.
Many of the deals ending include exit fees, but customers aren't often aware that market regulation allows you to switch suppliers once you get to within six weeks of the tariff end date without being charged a penalty fee.
As a result, MoneySuperMarket is recommending that people shop around and find a competitive tariff.
'At this time of year, as you're enjoying the hot weather and long summer evenings, energy bills are understandably the last thing on your mind, said Stephen Murray, energy expert at MoneySuperMarket.
"However, with a substantial number of fixed tariffs coming to an end in June and July, you should act now and lock into another fixed deal, whether that's with a new supplier or their existing one.
'You don't need to wait until the tariff expires - you can do it today. Switching online takes five minutes and it's an easy process, with savings of Â£250 or more to be made.'
For more information on switching energy suppliers, visit www.moneysupermarket.com