A total of nine dual fuel energy tariffs expire on 31 August and with eight of them, it will mean customers will see a hike in their bills.

Customers on these tariffs can expect a £135.17 price jump on average, that’s 14.5% more when rolled onto their suppliers’ standard variable tariff.

Gocompare Energy research also found that customers on the Scottish Power Online Fixed Energy August 2016 tariff will see the largest average UK rise with bills increased by a fifth.

Those that fail to shop around will see their bills rise by £183.10 – 20% from the £897.47 per year to £1,080.57.

In comparison, households under the British Gas Fixed Price August 2016 tariff will actually see their annual energy bill drop by £78.35 (6.98%).

This is because the standard tariff they will be rolled onto is cheaper than the deal they are currently on. While a £78.35 price drop might sound appealing to some, people could save more than three times that by shopping around and switching energy provider.

Ben Wilson, energy spokesperson at Gocompare.com, said: “With autumn approaching households should be looking ahead to ensure they’re not stung by a price rise as their usage begins to creep up. Back to school is an expensive time for any family, especially following the summer holidays where household finances are often stretched.

“Shopping around for a better energy deal only takes a few minutes and customers could save up to £292. There’s a host of really competitive fixed energy deals available right now, but with prices starting to creep up across the board, it’s unlikely many of them will be here for long, meaning customers should act fast to lock in savings.”

The top 10 cheapest dual fuel tariffs

Gocompare lists the 10 cheapest dual fuel tariffs paid by direct debit for medium users:

• Avro Energy Simple and Select fixed tariff costs £770. It has no early exit fees.
• So Energy So Falcon fixed tariff costs  £779. It’s £5 per fuel in early exit fees.
• GB Energy Supply Fixed 12 Crystal fixed tariff costs £780. It has no early exit fees.
• SSE 1 Year Fixed V8 fixed tariff costs £782. It’s £30 per fuel in early exit fees.
• Affect Energy Fixed Saver August 2017 costs £784. It’s £25 per fuel in early exit fees.
• Places for People Energy Together – September 2017 Fixed 35 costs £792. It’s £30 per fuel in early exit fees.
• Flow Energy Connect 8 Fixed tariff costs £792. It’s £30 per fuel in early exit fees.
• Octopus Energy 12M Fixed tariff costs £796. It has no early exit fees.
• Octopus Energy Flexible Octopus variable tariff costs £806. It has no early exit fees.
• Npower Online Price Fix September 2017 fixed tariff costs £806. It’s £20 per fuel in early exit fees.