The first 'reverse auction' - in which energy suppliers will bid to provide the 280,000 customers signed up to the scheme with their lowest price tariff - is due to take place on May 9.
Co-Operative Energy has also signed-up for the scheme after Which? altered its definition of the term "market leading" bid. The term now adds that an energy supplier can bid for the customers signed-up to the scheme with their current best deals.
EDF has already confirmed that it will be bidding at the Big Switch auction with its existing Blue +Price Promise tariff, according to This Is Money. The company has forecast that, based on average consumption, the fixed price plan would cost Â£1,054.20 per year.
Meanwhile, Scottish and Southern and British Gas have announced that they will not be partaking in the scheme.
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