Energy Secretary Ed Davey admits the plans won't make bills cheaper for everyone - but should make them simpler.
It is possible that some of the best deals on the market will disappear. We could lurch from a minefield of deals to virtually none at all.
Downing Street sources are adamant tomorrow's energy bills announcement will stick to David Cameron's promise of lower tariffs, but will it?
Ministers are poised to announce plans to decrease energy bills in a bid to get customers on the lowest tariffs available.