Families are paying £1.4bn more than they have to because of the gap. Photograph: Alamy Stock Photo
The gap between the best and worst energy tariffs offered by the big six suppliers has widened by more than half since a round of price hikes over the winter.
The difference between the firms’ cheapest fixed deals and their most expensive ones, standard variable tariffs, jumped from £70 last November on average to £109 in June, according to challenger supplier Bulb.
Standard variable tariffs landed the big six in the crosshairs of Theresa May, who promised to impose a price cap to address the “injustice” of families collectively paying £1.4bn over the odds because of the gap.
While plans for a cap have been hugely watered-down, the new figures could provide fuel for Greg Clark, business secretary, and Ofgem, the energy regulator, to take stronger action.
A spokesman for the Department of Business, Energy and Industrial Strategy said: “Energy customers should not be punished for their loyalty … We now want to see suppliers playing their part and supporting the regulator to deliver a fairer deal to customers on poor value tariffs.”
Bulb found that the gap, which it calls a “loyalty fee” because customers roll on to standard variable tariffs if no action is taken when fixed ones end, had widened the most at E.ON.
One of the worst examples in June was the £328.98 chasm between Npower’s cheapest deal and standard variable rate, for customers in Greater London.
However British Gas had no gap and EDF had actually narrowed the differential since November.
All of the big six, apart from British Gas, hiked their standard variable tariffs in the past six months. Some, such as SSE, have lost hundreds of thousands of customers as a result.
Hayden Wood, co-founder of Bulb, which has around 60,000 customers, said: “I’m disappointed that so many energy companies are still putting profits first and customers last.
“They shouldn’t lure customers with teaser rates and then hit them with prices hikes later. It’s just not right.”
The company looked at comparison site uSwitch to see the cheapest fix and the standard variable tariff for each of the big six across all regions on 25 November 2016 and 25 June 2016. As tariffs can change from day to day, the supplier admitted its analysis provided only a snapshot.
In response a spokesman for SSE said: “It is wrong to categorise this as a ‘big six issue’ when some of the largest differentials in the market belong to the smaller suppliers.”
E.ON said: “We’re always working hard to engage with our customers to make them aware of the different tariffs that might be appropriate for them … which our existing customers can switch to without charge.”
EDF said: “EDF Energy works hard to engage its customers and enable them to choose the most appropriate deal for themselves.”
ScottishPower said: “We will continue to work hard to offer customers good value products and continue to lead the large suppliers in encouraging customers to move away from standard tariffs.”
Npower said it was “proactive” in highlighting its cheapest tariffs to customers when their fixed deals are coming to an end. British Gas did not comment.
Despite blaming the big six for “rip-off” energy prices, the government admitted last week that the average annual dual fuel energy bill will rise by £2.30 next year because it is giving the steel, ceramics and cement industries a £100m exemption from subsidising clean energy projects.
Separately on Monday, a report warned that energy bills may rising if the UK quits the EU internal energy market during Brexit. “Electricity interconnection with the EU meets 7% of UK’s electricity needs and keeps consumer energy bills down,” the Green Alliance thinktank said.