Customers could save more than £200 a year if they switch energy suppliers, a new league table showing the worst deals on the market has revealed.
Industry watchdog Ofgem compared the most expensive standard tariffs with the cheapest deals on the market to provide greater transparency to consumers.
Their findings showed there is a £261 difference between Npower's standard variable tariff and its cheapest tariff, while customers of Co-operative Energy, Extra Energy, Npower, First Utility and Scottish Power could save in excess of £200 if they switch suppliers.
The release of the energy company league table follows a warning by the Competition and Markets Authority (CMA) in June that 70% of people were on the more expensive "default" standard variable tariff, costing consumers £1.4 bill.
Ofgem said last month that 66% of all households remain on standard variable tariffs.
Switching supplier: The difference between each supplier's standard variable tariff and the average of the cheapest tariffs from the 10 cheapest suppliers
- Extra Energy £260
- Co-operative Energy £252
- Scottish Power £211
- Npower £208
- First Utility £201
- EDF Energy £200
- SSE £198
- Ovo £194
- E-ON £187
- British Gas £174
- Utility Warehouse £143
Difference between a supplier's standard variable tariff and its cheapest tariff
- Npower £261
- Co-operative Energy £245
- First Utility £157
- Extra Energy £154
- Utility Warehouse £150
- EDF Energy £136
- Scottish Power £129
- British Gas £129
- SSE £98
- Ovo £67
- E-ON £41
Energy Secretary Greg Clark said the table will instantly show consumers where they can save money and increase transparency around the "millions" of Britons who are overpaying for their energy by remaining on the expensive standard variable tariffs.
He said: "Millions of people across Britain continue to pay too much for their energy. The measures announced today are a positive step to help more people benefit from increased choice and competition.
"As the Government has made clear, where markets are not working for consumers - in energy or otherwise - we are prepared to act."
Energy UK chief executive Lawrence Slade said: "A record number of people have switched electricity supplier in 2016. This is fantastic progress, but more needs to be done.
"Over 40 companies across the industry, big and small, are working hard to win customers. I'd encourage everyone to look at the best deal for them, whether that is one that offers a lower price or better customer service, there are choices for everyone."