Energy customers to be told if they are not on best deal The Deputy Prime Minister will say it is unacceptable that families struggling to cope with rising household costs are not told that cheaper fuel tariffs are available. The country's six big energy firms, which supply 99 per cent of homes, offer more than 120 different tariffs. Seven in 10 customers are not on the best deal and could save an average of more than £100 each annually by switching. In a speech today, Mr Clegg will say: "We can't control volatile world energy prices but we can still help people get their bills down. So I can announce today that we have secured a landmark deal with the six big energy companies to give customers a guaranteed offer of the best tariff for them. Under the scheme, every household will be warned at least once a year if they should switch tariffs. The Deputy Prime Minister will add that the Government is working to put bar codes on energy bills that can be read by smart phones. This will enable energy usage to be scrutinised by a specialist website which can calculate if someone would save money by switching to another firm. Mr Clegg will also insist that efforts to advance the use of green energy sources such as wind and solar are essential, despite them being blamed for adding to energy bills.