Analysis by comparison site MoneySupermarket.com revealed that a number of fixed rate deals will end over the next month, with bill payers running the risk of a bill shock when reverting to their providers’ standard tariff.

Households who signed up to npower’s Go Fix 11 tariff stand to come out worse off if they become complacent.

The tariff, which was introduced in February 2012, offered an average bill of £1,033.19. However, customers have until 21st May to move to another deal otherwise they risk being swiftly moved on to the suppliers standard tariff with an average bill of £1,352.23 – a hike of nearly £320.

MoneySupermarket says the trend for longer term fixed rate tariffs seems to have gathered pace with all of the ‘Big Six’ energy suppliers offering deals to fix prices over the long term. 

Clare Francis, editor-in-chief at MoneySupermarket.com, said: “There are a large number of fixed rate energy deals coming to an end over the next month and now is the time to take action before you see your bills rocket.

“Most people will be moved onto their provider’s standard price plan unless they take action so in order to avoid a bill shock it’s well worth taking 10 minutes to find a new deal to move onto. There are a number of new fixed rate products available to customers over the short and long term with savings up to £177 to be made by switching.”

Households should note that all energy suppliers have a duty to inform their fixed rate customers that their tariff is about to end 30 days before it expires.

Francis added: “If you haven’t received a notification from your provider but think yours ends soon, contact them immediately to find out exactly when it finishes. The simplest way to find out which new tariff will be the best one for you is to use a comparison site.

“With prices expected to continue to rise, we recommend going for a fixed online deal, to protect you from future price rises as opposed to a variable rate deal. You might pay slightly more initially but over the term of the deal it will probably offer better value for money.

“As well as saving money by switching tariff it’s also worth thinking about how you use energy at home. Making simple changes such as doing your washing at 30 degrees rather than 40 or 60, and turning appliances off as opposed to leaving them on standby, can result in significant savings over the year.”