It claims residential electricity customers not on a mains gas supply will see their bills reduced by an average of £14.
Graham Bartlett, managing director of E.ON's retail business, said the firm is "always looking" to price its gas and electricity "as fairly and competitively as possible".
He added: "However, we, like Ofgem, saw that our electricity customers who have no mains gas are simply not able to get some of our best deals. That's why we've decided to level the playing field in our core regions by passing on this special reduction."
Last month, E.ON announced that mining had begun at all eight caverns of the firm's Holford gas storage facility in Cheshire.
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