Research from auto-switching firm Look After My Bills revealed 112 fixed energy deals end on Sunday (30 June), with people on these tariffs rolled onto their supplier’s pricier standard tariff.

Customers on Shell Energy Smart First June 2019 – Online will face the biggest hike with their bills rising from £907 to £1,254 overnight, a 38 per cent increase.

Six of the 10 biggest price rises come from green energy supplier Engie (see table below).

This year is set to be the worst on record for energy price rises meaning it’s more important than ever to switch to a better deal when your tariff comes to an end.

Separate research from Look After My Bills this week revealed 42 energy suppliers hiked prices in the first six months of 2019 alone.

The average price hike stands at £110, compared to an average rise of £75 in 2018.

Simona Rutkauskaite from Look After My Bills said: “This is the worst month this year for the loyalty penalty.

“A combination of price rises and a huge number of fixed tariffs ending means hundreds of thousands face a shock to their bills.

“People are lured into fixed contracts with competitive rates and at the end of their contract find themselves punished with tremendous price hikes. It’s a loyalty trap.”

Top ten biggest bill price jumps

What is a standard variable or default tariff?

All energy suppliers have a standard variable, default or ‘evergreen’ tariff. This is the tariff you’ll be switched to if you don’t take action when a fixed-term deal comes to an end.

Suppliers can hike prices on standard tariffs whenever they choose – as long as typical bills don’t exceed the price cap. However, it’s free to switch away from a standard variable tariff as they don’t have exit fees.

In most cases, households will be better off switching to a dual fuel tariff run online and paid by monthly direct debit. Deals change frequently but the ‘big six’ (British Gas, E.ON, Npower, Scottish Power, Scottish & Southern and EDF Energy) tend to be more expensive than smaller brands.