It has also been claimed that younger people may choose to fall into debt while paying their bills.
Adam Scorer, campaigns director of energywatch, stated that the review demonstrated how consumers are faced with "three evils".
He added: "The review also shows how understanding the actual experience of consumers can help a wide range of agencies anticipate and support households in fuel poverty."
Details about the new study have come after energywatch also published its final annual report.
In the study, the organisation claimed that prepayment customers are paying more for energy than those on online tariffs.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.