Deputy prime minister Nick Clegg today unveiled a new system under which energy companies will be required to let customers know what their best deal is.
The move could save households up to £100 a year, according to ministers who have been calling for the change.
Energy companies will be obliged to tell people about the most economic tariff for them.
Clegg said seven out of 10 people have the wrong deal and pay too much.
Under the deal, British Gas, E.On, NPower, Scottish and Southern Energy, EDF and Scottish Power will contact their customers once a year to tell them their best deal.